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Sample records for field dynamic hysteresis

  1. Dynamic hysteresis behaviors for the two-dimensional mixed spin (2, 5/2) ferrimagnetic Ising model in an oscillating magnetic field

    Science.gov (United States)

    Ertaş, Mehmet

    2015-09-01

    Keskin and Ertaş (2009) presented a study of the magnetic properties of a mixed spin (2, 5/2) ferrimagnetic Ising model within an oscillating magnetic field. They employed dynamic mean-field calculations to find the dynamic phase transition temperatures, the dynamic compensation points of the model and to present the dynamic phase diagrams. In this work, we extend the study and investigate the dynamic hysteresis behaviors for the two-dimensional (2D) mixed spin (2, 5/2) ferrimagnetic Ising model on a hexagonal lattice in an oscillating magnetic field within the framework of dynamic mean-field calculations. The dynamic hysteresis curves are obtained for both the ferromagnetic and antiferromagnetic interactions and the effects of the Hamiltonian parameters on the dynamic hysteresis behaviors are discussed in detail. The thermal behaviors of the coercivity and remanent magnetizations are also investigated. The results are compared with some theoretical and experimental works and a qualitatively good agreement is found. Finally, the dynamic phase diagrams depending on the frequency of an oscillating magnetic field in the plane of the reduced temperature versus magnetic field amplitude is examined and it is found that the dynamic phase diagrams display richer dynamic critical behavior for higher values of frequency than for lower values.

  2. Thermal behavior of dynamic magnetizations, hysteresis loop areas and correlations of a cylindrical Ising nanotube in an oscillating magnetic field within the effective-field theory and the Glauber-type stochastic dynamics approach

    International Nuclear Information System (INIS)

    Deviren, Bayram; Keskin, Mustafa

    2012-01-01

    The dynamical aspects of a cylindrical Ising nanotube in the presence of a time-varying magnetic field are investigated within the effective-field theory with correlations and Glauber-type stochastic approach. Temperature dependence of the dynamic magnetizations, dynamic total magnetization, hysteresis loop areas and correlations are investigated in order to characterize the nature of dynamic transitions as well as to obtain the dynamic phase transition temperatures and compensation behaviors. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and core, i.e., five different types of compensation behaviors in the Néel classification nomenclature exist in the system. -- Highlights: ► Kinetic cylindrical Ising nanotube is investigated using the effective-field theory. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► The effects of the exchange interactions have been studied in detail. ► Five different types of compensation behaviors have been found. ► Some characteristic phenomena are found depending on ratio of physical parameters.

  3. Thermal behavior of dynamic magnetizations, hysteresis loop areas and correlations of a cylindrical Ising nanotube in an oscillating magnetic field within the effective-field theory and the Glauber-type stochastic dynamics approach

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram, E-mail: bayram.deviren@nevsehir.edu.tr [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-02-20

    The dynamical aspects of a cylindrical Ising nanotube in the presence of a time-varying magnetic field are investigated within the effective-field theory with correlations and Glauber-type stochastic approach. Temperature dependence of the dynamic magnetizations, dynamic total magnetization, hysteresis loop areas and correlations are investigated in order to characterize the nature of dynamic transitions as well as to obtain the dynamic phase transition temperatures and compensation behaviors. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and core, i.e., five different types of compensation behaviors in the Néel classification nomenclature exist in the system. -- Highlights: ► Kinetic cylindrical Ising nanotube is investigated using the effective-field theory. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► The effects of the exchange interactions have been studied in detail. ► Five different types of compensation behaviors have been found. ► Some characteristic phenomena are found depending on ratio of physical parameters.

  4. Hysteresis

    OpenAIRE

    Mark Setterfield

    2010-01-01

    Three competing conceptualizations of hysteresis in economics are identified: the unit/zero root approach, “true” hysteresis, and hysteresis conceived as a product of historical time. The properties of these conceptualizations are discussed and their pros and cons considered.

  5. Dynamic magnetic hysteresis behavior and dynamic phase transition in the spin-1 Blume-Capel model

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram, E-mail: bayram.deviren@nevsehir.edu.tr [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-03-15

    The nature (time variation) of response magnetization m(wt) of the spin-1 Blume-Capel model in the presence of a periodically varying external magnetic field h(wt) is studied by employing the effective-field theory (EFT) with correlations as well as the Glauber-type stochastic dynamics. We determine the time variations of m(wt) and h(wt) for various temperatures, and investigate the dynamic magnetic hysteresis behavior. We also investigate the temperature dependence of the dynamic magnetization, hysteresis loop area and correlation near the transition point in order to characterize the nature (first- or second-order) of the dynamic transitions as well as obtain the dynamic phase transition temperatures. The hysteresis loops are obtained for different reduced temperatures and we find that the areas of the loops are decreasing with the increasing of the reduced temperatures. We also present the dynamic phase diagrams and compare the results of the EFT with the results of the dynamic mean-field approximation. The phase diagrams exhibit many dynamic critical points, such as tricritical ( Bullet ), zero-temperature critical (Z), triple (TP) and multicritical (A) points. According to values of Hamiltonian parameters, besides the paramagnetic (P), ferromagnetic (F) fundamental phases, one coexistence or mixed phase region, (F+P) and the reentrant behavior exist in the system. The results are in good agreement with some experimental and theoretical results. - Highlights: Black-Right-Pointing-Pointer Kinetic spin-1 Blume-Capel model is studied using the effective-field theory. Black-Right-Pointing-Pointer We investigated the dynamic magnetic hysteresis behavior. Black-Right-Pointing-Pointer Dynamic magnetization, hysteresis loop area and correlation are investigated. Black-Right-Pointing-Pointer System exhibits tricritical, zero-temperature, triple and multicritical points. Black-Right-Pointing-Pointer We present the dynamic phase diagrams and compare the results of the EFT

  6. Dynamic hysteresis modeling including skin effect using diffusion equation model

    Energy Technology Data Exchange (ETDEWEB)

    Hamada, Souad, E-mail: souadhamada@yahoo.fr [LSP-IE: Research Laboratory, Electrical Engineering Department, University of Batna, 05000 Batna (Algeria); Louai, Fatima Zohra, E-mail: fz_louai@yahoo.com [LSP-IE: Research Laboratory, Electrical Engineering Department, University of Batna, 05000 Batna (Algeria); Nait-Said, Nasreddine, E-mail: n_naitsaid@yahoo.com [LSP-IE: Research Laboratory, Electrical Engineering Department, University of Batna, 05000 Batna (Algeria); Benabou, Abdelkader, E-mail: Abdelkader.Benabou@univ-lille1.fr [L2EP, Université de Lille1, 59655 Villeneuve d’Ascq (France)

    2016-07-15

    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.

  7. Dynamical hysteresis and spatial synchronization in coupled non ...

    Indian Academy of Sciences (India)

    ... via mutual synchronization indices reveals that one attractor corresponds to spatially synchronized oscillators, while the other corresponds to desynchronized oscillators. Dynamical hysteresis may thus help to understand critical aspects of the dynamical behavior of complex biological systems, e.g. seizures in the epileptic ...

  8. Instantaneous stiffness and hysteresis of dynamic elastic response prosthetic feet.

    Science.gov (United States)

    Webber, Christina M; Kaufman, Kenton

    2017-10-01

    Dynamic elastic response prosthetic feet are designed to mimic the functional characteristics of the native foot/ankle joint. Numerous designs of dynamic elastic response feet exist which make the prescription process difficult, especially because of the lack of empirical evidence describing the objective performance characteristics of the feet. To quantify the mechanical properties of available dynamic elastic response prosthetic feet, specifically the stiffness and hysteresis. Mechanical testing of dynamic elastic response prosthetic feet. Static Proof Testing in accordance with ISO 10328 was conducted on seven dynamic elastic response prosthetic feet. Load-displacement data were used to calculate the instantaneous stiffness in both the heel and forefoot regions, as well as hysteresis associated with each foot. Heel stiffness was greater than forefoot stiffness for all feet. The heel of the glass composite prosthetic foot was stiffer than the carbon fiber feet and it exhibited less hysteresis. Two different carbon fiber feet had the stiffest forefoot regions. Mechanical testing is a reproducible method that can be used to provide objective evidence about dynamic elastic response prosthetic foot performance and aid in the prescription process. Clinical relevance The quantitative stiffness and hysteresis data from this study can be used by prosthetists to aid the prescription process and make it more objective.

  9. Dynamical hysteresis and spatial synchronization in coupled non ...

    Indian Academy of Sciences (India)

    behavior of complex biological systems, e.g. seizures in the epileptic brain can be viewed as transitions between different dynamical phases caused by time dependence in the brain's internal coupling. Keywords. Hysteresis; multistability; spatial synchronization; spatio-temporal chaos. PACS Nos 05.45.Xt; 05.45.tp; 05.45.

  10. Magnetic fluid hyperthermia probed by both calorimetric and dynamic hysteresis measurements

    Energy Technology Data Exchange (ETDEWEB)

    Guibert, Clément; Fresnais, Jérôme; Peyre, Véronique; Dupuis, Vincent, E-mail: vincent.dupuis@upmc.fr

    2017-01-01

    In this paper, we report an investigation of magnetic fluid hyperthermia (MFH) using combined calorimetric and newly implemented dynamic hysteresis measurements for two sets of well characterized size-sorted maghemite nanoparticles (with diameters of about 10 nm and 20 nm) dispersed in water and in glycerol. Our primary goal was to assess the influence of viscosity on the heating efficiency of magnetic nanoparticles described in terms of specific loss power (SLP or specific absorption rate, SAR) and dynamic hysteresis. In particular, we aimed to investigate how this SLP depends on the transition from Néelian to Brownian behavior of nanoparticles expected to occur between 10 nm and 20 nm (for maghemite) and dependent on the viscosity. While we observed a good agreement between calorimetric and dynamic hysteresis measurements, we found that the SLP measured for the different systems do not depend noticeably on the viscosity of solvent. Calculations performed according to Rosensweig's linear model [1] allow us to quantitatively reproduce our results at low field intensities, provided we use a value for the magnetic anisotropy constant much smaller than the one commonly used in the literature. This raises the question of the temperature dependance of the magnetic anisotropy constant and its relevance for a quantitative description of MFH. - Highlights: • Dynamic hysteresis measurements are a promising tool to study magnetic hyperthermia. • Dynamic hysteresis cycles can be reproduced using a simple model. • The effect of viscosity on hyperthermia of maghemite is weaker than expected.

  11. Neural networks dynamic hysteresis model for piezoceramic actuator based on hysteresis operator of first-order differential equation

    International Nuclear Information System (INIS)

    Dang Xuanju; Tan Yonghong

    2005-01-01

    A new neural networks dynamic hysteresis model for piezoceramic actuator is proposed by combining the Preisach model with diagonal recurrent neural networks. The Preisach model is based on elementary rate-independent operators and is not suitable for modeling piezoceramic actuator across a wide frequency band because of the rate-dependent hysteresis characteristic of the piezoceramic actuator. The structure of the developed model is based on the structure of the Preisach model, in which the rate-independent relay hysteresis operators (cells) are replaced by the rate-dependent hysteresis operators of first-order differential equation. The diagonal recurrent neural networks being modified by an adjustable factor can be used to model the hysteresis behavior of the pizeoceramic actuator because its structure is similar to the structure of the modified Preisach model. Therefore, the proposed model not only possesses that of the Preisach model, but also can be used for describing its dynamic hysteresis behavior. Through the experimental results of both the approximation and the prediction, the effectiveness of the neural networks dynamic hysteresis model for the piezoceramic actuator is demonstrated

  12. Open-loop position tracking control of a piezoceramic flexible beam using a dynamic hysteresis compensator

    International Nuclear Information System (INIS)

    Nguyen, Phuong-Bac; Choi, Seung-Bok

    2010-01-01

    This paper proposes a novel hysteresis compensator to enhance control accuracy in open-loop position tracking control of a piezoceramic flexible beam. The proposed hysteresis compensator consists of two components: a rate-independent hysteresis compensator and a nonlinear filter. The compensator is formulated based on the inverse Preisach model, while the weight coefficients of the filter are identified adaptively using a recursive least square (RLS) algorithm. In this work, two dynamic hysteresis compensators (or rate-independent hysteresis compensators) are developed by adopting two different nonlinear filters: Volterra and bilinear filters. In order to demonstrate the improved control accuracy of the proposed dynamic compensators, a flexible beam associated with the piezoceramic actuator is modeled using the finite element method (FEM) and Euler–Bernoulli beam theory. The beam model is then integrated with the proposed hysteresis model to achieve accurate position tracking control at the tip of the beam. An experimental investigation on the tip position tracking control is undertaken by realizing three different hysteresis compensators: a rate-independent hysteresis compensator, a rate-dependent hysteresis compensator with a Volterra nonlinear filter and a rate-independent hysteresis compensator with a bilinear nonlinear filter. It is shown that the proposed dynamic hysteresis compensators can provide much better tracking control accuracy than conventional rate-independent hysteresis compensators

  13. Polarization extension mechanism revealed through dynamic ferroelectric hysteresis and electric field driven structural distortions in lead free Na0.5Bi0.5TiO3 ceramic

    Science.gov (United States)

    Karthik, T.; Asthana, Saket

    2017-09-01

    The electric field amplitude (E o) dependent dynamic ferroelectric hysteresis and polarization current density curves measured at room temperature for Na0.5Bi0.5TiO3 (NBT), showed three different stages of polarization reversal mechanism. The scaling relationship confirmed the dominance of domain wall motion at Stage I (i.e. upto E o  <  35 kV cm-1), followed by domain switching at Stage II (35 kV cm-1  <  E o  <  60 kV cm-1). Interestingly, a unique behaviour with two sub stages was observed in Stage III (60 kV cm-1  <  E o  <  90 kV cm-1), with two distinct switching mechanisms viz., polarization rotation at Stage III-A and polarization extension at Stage III-B. X-ray diffraction analysis based on the Rietveld refined atomic positional co-ordinates, in electrically poled system strongly favors the polarization extension mechanism proposed at Stage III-B. The measured E o-dependent longitudinal piezoelectric response (d 33 and g33) values match closely with our proposed polarization reversal mechanism.

  14. Magnetic fluid hyperthermia probed by both calorimetric and dynamic hysteresis measurements

    Science.gov (United States)

    Guibert, Clément; Fresnais, Jérôme; Peyre, Véronique; Dupuis, Vincent

    2017-01-01

    In this paper, we report an investigation of magnetic fluid hyperthermia (MFH) using combined calorimetric and newly implemented dynamic hysteresis measurements for two sets of well characterized size-sorted maghemite nanoparticles (with diameters of about 10 nm and 20 nm) dispersed in water and in glycerol. Our primary goal was to assess the influence of viscosity on the heating efficiency of magnetic nanoparticles described in terms of specific loss power (SLP or specific absorption rate, SAR) and dynamic hysteresis. In particular, we aimed to investigate how this SLP depends on the transition from Néelian to Brownian behavior of nanoparticles expected to occur between 10 nm and 20 nm (for maghemite) and dependent on the viscosity. While we observed a good agreement between calorimetric and dynamic hysteresis measurements, we found that the SLP measured for the different systems do not depend noticeably on the viscosity of solvent. Calculations performed according to Rosensweig's linear model [1] allow us to quantitatively reproduce our results at low field intensities, provided we use a value for the magnetic anisotropy constant much smaller than the one commonly used in the literature. This raises the question of the temperature dependance of the magnetic anisotropy constant and its relevance for a quantitative description of MFH.

  15. Low Field Magnetic and Thermal Hysteresis in Antiferromagnetic Dysprosium

    Directory of Open Access Journals (Sweden)

    Iuliia Liubimova

    2017-06-01

    Full Text Available Magnetic and thermal hysteresis (difference in magnetic properties on cooling and heating have been studied in polycrystalline Dy (dysprosium between 80 and 250 K using measurements of the reversible Villari effect and alternating current (AC susceptibility. We argue that measurement of the reversible Villari effect in the antiferromagnetic phase is a more sensitive method to detect magnetic hysteresis than the registration of conventional B(H loops. We found that the Villari point, recently reported in the antiferromagnetic phase of Dy at 166 K, controls the essential features of magnetic hysteresis and AC susceptibility on heating from the ferromagnetic state: (i thermal hysteresis in AC susceptibility and in the reversible Villari effect disappears abruptly at the temperature of the Villari point; (ii the imaginary part of AC susceptibility is strongly frequency dependent, but only up to the temperature of the Villari point; (iii the imaginary part of the susceptibility drops sharply also at the Villari point. We attribute these effects observed at the Villari point to the disappearance of the residual ferromagnetic phase. The strong influence of the Villari point on several magnetic properties allows this temperature to be ranked almost as important as the Curie and Néel temperatures in Dy and likely also for other rare earth elements and their alloys.

  16. An efficient hysteresis modeling methodology and its implementation in field computation applications

    Energy Technology Data Exchange (ETDEWEB)

    Adly, A.A., E-mail: adlyamr@gmail.com [Electrical Power and Machines Dept., Faculty of Engineering, Cairo University, Giza 12613 (Egypt); Abd-El-Hafiz, S.K. [Engineering Mathematics Department, Faculty of Engineering, Cairo University, Giza 12613 (Egypt)

    2017-07-15

    Highlights: • An approach to simulate hysteresis while taking shape anisotropy into consideration. • Utilizing the ensemble of triangular sub-regions hysteresis models in field computation. • A novel tool capable of carrying out field computation while keeping track of hysteresis losses. • The approach may be extended for 3D tetra-hedra sub-volumes. - Abstract: Field computation in media exhibiting hysteresis is crucial to a variety of applications such as magnetic recording processes and accurate determination of core losses in power devices. Recently, Hopfield neural networks (HNN) have been successfully configured to construct scalar and vector hysteresis models. This paper presents an efficient hysteresis modeling methodology and its implementation in field computation applications. The methodology is based on the application of the integral equation approach on discretized triangular magnetic sub-regions. Within every triangular sub-region, hysteresis properties are realized using a 3-node HNN. Details of the approach and sample computation results are given in the paper.

  17. Field rotor measurements. Data sets prepared for analysis of stall hysteresis

    Energy Technology Data Exchange (ETDEWEB)

    Aagaard Madsen, H.; Thirstrup Petersen, J. [Risoe National Lab. (Denmark); Bruining, A. [Delft Univ. of Technology (Netherlands); Brand, A. [ECN (Netherlands); Graham, M. [Imperical College (United Kingdom)

    1998-05-01

    As part of the JOULE-3 project `STALLVIB` an analysis and synthesis of the data from the field rotor experiments at ECN, Delft University, Imperial College, NREL and Risoe has been carried out. This has been done in order to see to what extent the data could be used for further development and validation of engineering dynamic stall models. A detailed investigation of the influence of the post-processing of the different data sets has been performed. Further, important statistical functions such as PSD spectra, coherence and transfer functions have been derived for the data sets which can be used as basis for evaluation of the quality of the data seen relative to actual application of the data. The importance of using an appropriate low-pass filtering to remove high frequency noise has been demonstrated when the relation between instantaneous values of e.g. {alpha} and C{sub N} is considered. In general, the complicated measurement on a rotor of {alpha} and w and the interpretation of these parameters combined with the strongly three-dimensional, turbulent flow field around the rotating blade has the consequence that it seems difficult to derive systematic information from the different data sets about stall hysteresis. In particular, the measurement of {alpha}, which determination of the stagnation point gives reasonable data below stall but fails in stall. On the other hand, measurements of {alpha} with a five hole pitot tube can be used also in the stall region. Another main problem is the non-dimensionalization of the coefficients C{sub N} and C{sub r}. If the dynamic pressure used for the non-dimensionalization is not fully correlated with the aerodynamic pressure over the considered airfoil section due to e.g. influence of the gravity on the pressure pipes, the hysteresis loops will be distorted. However, using the data with caution and applying a suitable post-processing as described by the different participants, it will probably be possible to obtain some

  18. Magnetic hysteresis and domain wall dynamics in single chain magnets with antiferromagnetic interchain coupling

    Energy Technology Data Exchange (ETDEWEB)

    Bukharov, A A; Ovchinnikov, A S; Baranov, N V [Department of Physics, Ural State University, Ekaterinburg, 620083 (Russian Federation); Inoue, K [Institute for Advanced Materials Research, Hiroshima University, Hiroshima (Japan)

    2010-11-03

    Using Monte Carlo simulations we investigate magnetic hysteresis in two- and three-dimensional systems of weakly antiferromagnetically coupled spin chains based on a scenario of domain wall (kink) motion within the chains. By adapting the model of walkers to simulate the domain wall dynamics and using the Ising-like dipole-dipole model, we study the effects of interchain coupling, temperature and anisotropy axis direction on hysteresis curves.

  19. Hysteresis in single-layer MoS2 field effect transistors.

    Science.gov (United States)

    Late, Dattatray J; Liu, Bin; Matte, H S S Ramakrishna; Dravid, Vinayak P; Rao, C N R

    2012-06-26

    Field effect transistors using ultrathin molybdenum disulfide (MoS(2)) have recently been experimentally demonstrated, which show promising potential for advanced electronics. However, large variations like hysteresis, presumably due to extrinsic/environmental effects, are often observed in MoS(2) devices measured under ambient environment. Here, we report the origin of their hysteretic and transient behaviors and suggest that hysteresis of MoS(2) field effect transistors is largely due to absorption of moisture on the surface and intensified by high photosensitivity of MoS(2). Uniform encapsulation of MoS(2) transistor structures with silicon nitride grown by plasma-enhanced chemical vapor deposition is effective in minimizing the hysteresis, while the device mobility is improved by over 1 order of magnitude.

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

    Science.gov (United States)

    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.

  1. Comparison of hysteresis loop area scaling behavior of Co/Pt multilayers: Discrete and continuous field sweeping

    Energy Technology Data Exchange (ETDEWEB)

    Handoko, Djati; Lee, Sang-Hyuk [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Min Lee, Kyung; Jeong, Jong-Ryul [Department of Material Science and Engineering and Graduate School of Green Energy Technology, Chungnam National University, Daejeon 305-764 (Korea, Republic of); Kim, Dong-Hyun, E-mail: donghyun@chungbuk.ac.kr [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of)

    2014-02-15

    We have investigated the hysteresis loop shape changes with discrete and continuous magnetic field sweeping for Co/Pt multilayers with a perpendicular magnetic anisotropy. The hysteresis loop shape was observed by measuring a polar magneto-optical Kerr effect. The loop area has been found to increase rapidly with an increase of the field step size as well as the sweeping frequency until the area reaches a maximum. The increase of the loop area has been analyzed based on the Steinmetz law, where a loop area scaling exponent determined from discrete field sweeping is compared to a scaling exponent from continuous field sweeping. The dynamic coercivity behavior with respect to discrete and continuous field sweeping is analyzed together with the loop area scaling behavior, suggesting that details of magnetic configuration disorders do not modify the loop area scaling exponent. - Highlights: • Co/Pt thin film multilayers with perpendicular magnetic anisotropy have been prepared. • Discrete and continuous field sweeping is applied for MOKE measurement. • Loop area scaling exponent is observed. • The dynamic coercivity behavior is analyzed together with the loop area scaling behavior. • Disorder details of magnetic configuration do not modify the loop area scaling exponent.

  2. Droplet evaporation dynamics on a superhydrophobic surface with negligible hysteresis.

    Science.gov (United States)

    Dash, Susmita; Garimella, Suresh V

    2013-08-27

    We report on experiments of droplet evaporation on a structured superhydrophobic surface that displays very high contact angle (CA ∼ 160 deg), and negligible contact angle hysteresis (evaporation is observed to occur in a constant-contact-angle mode, with contact radius shrinking for almost the entire duration of evaporation. Experiments conducted on Teflon-coated smooth surface (CA ∼ 120 deg) as a baseline also support an evaporation process that is dominated by a constant-contact-angle mode. The experimental results are compared with an isothermal diffusion model for droplet evaporation from the literature. Good agreement is observed for the Teflon-coated smooth surface between the analytical expression and experimental results in terms of the total time for evaporation, transient volume, contact angle, and contact radius. However, for the structured superhydrophobic surface, the experiments indicate that the time taken for complete evaporation of the droplet is greater than the predicted time, across all droplet volumes. This disparity is attributed primarily to the evaporative cooling at the droplet interface due to the high aspect ratio of the droplet and also the lower effective thermal conductivity of the substrate due to the presence of air gaps. This hypothesis is verified by numerically evaluating the temperature distribution along the droplet interface. We propose a generalized relation for predicting the instantaneous volume of droplets with initial CA > 90 deg, irrespective of the mode of evaporation.

  3. Random crystal field effect on the magnetic and hysteresis behaviors of a spin-1 cylindrical nanowire

    Energy Technology Data Exchange (ETDEWEB)

    Zaim, N.; Zaim, A., E-mail: ah_zaim@yahoo.fr; Kerouad, M., E-mail: kerouad@fs-umi.ac.ma

    2017-02-15

    In this work, the magnetic behavior of the cylindrical nanowire, consisting of a ferromagnetic core of spin-1 atoms surrounded by a ferromagnetic shell of spin-1 atoms is studied in the presence of a random crystal field interaction. Based on Metropolis algorithm, the Monte Carlo simulation has been used to investigate the effects of the concentration of the random crystal field p, the crystal field D and the shell exchange interaction J{sub s} on the phase diagrams and the hysteresis behavior of the system. Some characteristic behaviors have been found, such as the first and second-order phase transitions joined by tricritical point for appropriate values of the system parameters, triple and isolated critical points can be also found. Depending on the Hamiltonian parameters, single, double and para hysteresis regions are explicitly determined. - Highlights: • Phase diagrams of a ferromagnetic nanowire are examined by the Monte Carlo simulation. • Different types of the phase diagrams are obtained. • The effect of the random crystal field on the hysteresis loops is studied. • Single, double and para hysteresis regions are explicitly determined.

  4. Calculation of the magnetic field in the active zone of a hysteresis clutch

    Science.gov (United States)

    Ermilov, M. A.; Glukhov, O. M.

    1977-01-01

    The initial distribution of magnetic induction in the armature stationary was calculated relative to the polar system of a hysteresis clutch. Using several assumptions, the problem is reduced to calculating the static magnetic field in the ferromagnetic plate with finite and continuous magnetic permeability placed in the air gap between two identical, parallel semiconductors with rack fixed relative to the tooth or slot position.

  5. Scaling behavior of hysteresis in multilayer MoS{sub 2} field effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Li, Tao; Du, Gang; Zhang, Baoshun; Zeng, Zhongming, E-mail: zmzeng2012@sinano.ac.cn [Key Laboratory of Nanodevices and Applications, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Ruoshui Road 398, Suzhou 215123 (China)

    2014-09-01

    Extrinsic hysteresis effects are often observed in MoS{sub 2} field effect devices due to adsorption of gas molecules on the surface of MoS{sub 2} channel. Scaling is a common method used in ferroics to quantitatively study the hysteresis. Here, the scaling behavior of hysteresis in multilayer MoS{sub 2} field effect transistors with a back-gated configuration was investigated. The power-law scaling relations were obtained for hysteresis area (〈A〉) and memory window (ΔV) with varying the region of back-gate voltage (V{sub bg,max}). It is interesting to find that the transition voltage in the forward sweep (V{sub FW}) and in the backward sweep (V{sub BW}) shifted to the opposite directions of back-gate voltage (V{sub bg}) with increasing V{sub bg,max}. However, when decreasing V{sub bg,max}, V{sub FW} shifted to positive and reversibly recovered, but V{sub BW} almost kept unchanged. The evolution of 〈A〉, ΔV, V{sub FW,} and V{sub BW} with V{sub bg,max} were discussed by the electrons transferring process between the adsorbate and MoS{sub 2} channel.

  6. Effect of External Economic-Field Cycle and Market Temperature on Stock-Price Hysteresis: Monte Carlo Simulation on the Ising Spin Model

    Science.gov (United States)

    Punya Jaroenjittichai, Atchara; Laosiritaworn, Yongyut

    2017-09-01

    In this work, the stock-price versus economic-field hysteresis was investigated. The Ising spin Hamiltonian was utilized as the level of ‘disagreement’ in describing investors’ behaviour. The Ising spin directions were referred to an investor’s intention to perform his action on trading his stock. The periodic economic variation was also considered via the external economic-field in the Ising model. The stochastic Monte Carlo simulation was performed on Ising spins, where the steady-state excess demand and supply as well as the stock-price were extracted via the magnetization. From the results, the economic-field parameters and market temperature were found to have significant effect on the dynamic magnetization and stock-price behaviour. Specifically, the hysteresis changes from asymmetric to symmetric loops with increasing market temperature and economic-field strength. However, the hysteresis changes from symmetric to asymmetric loops with increasing the economic-field frequency, when either temperature or economic-field strength is large enough, and returns to symmetric shape at very high frequencies. This suggests competitive effects among field and temperature factors on the hysteresis characteristic, implying multi-dimensional complicated non-trivial relationship among inputs-outputs. As is seen, the results reported (over extensive range) can be used as basis/guideline for further analysis/quantifying how economic-field and market-temperature affect the stock-price distribution on the course of economic cycle.

  7. A Novel Hysteresis Model of Magnetic Field Strength Determined by Magnetic Induction Intensity for Fe-3% Si Electrical Steel Applied in Cigarette Making Machines

    Directory of Open Access Journals (Sweden)

    Hao Wang

    2016-01-01

    Full Text Available Hysteresis characteristics of grain-oriented electrical steel were studied through the hysteresis loop. Existing hysteresis fitting simulation methods were summarized, and new Fe-3% Si grain-oriented electrical steel hysteresis loop model was proposed. Undetermined coefficients of the magnetic field intensity and magnetic flux density were determined by both the fixed angle method and the least squares method, and the hysteresis loop model was validated with high fitting degree by experimental data.

  8. Hysteresis loop signatures of phase transitions in a mean-field model of disordered Ising magnet

    Science.gov (United States)

    Timonin, P. N.

    2010-06-01

    The multiplicity of long-lived states in frustrated disordered magnets makes the task to experimentally deter-mine which of them has the lowest free energy (and thus what thermodynamic phase the sample is in) seem rather hopeless. Nevertheless here we show in the framework of Landau-type phenomenological model that signatures of the mean-field equilibrium phase transitions in such highly nonequilibrium systems may be found in the evolution of the hysteresis loop form. Thus the sequence of transitions from spin-glass to mixed phase and to ferromagnetic one results in the changes from inclined hysteresis loop to that with the developing vertical sides and to one with the perfectly vertical sides. Such relation between loop form and the location of global minimum may hold beyond the mean-field approximation and can be useful in the real experiments and Monte-Carlo simulations of the problems involving rugged potential landscape.

  9. Hysteresis mechanism and control in pentacene organic field-effect transistors with polymer dielectric

    Directory of Open Access Journals (Sweden)

    Wei Huang

    2013-05-01

    Full Text Available Hysteresis mechanism of pentacene organic field-effect transistors (OFETs with polyvinyl alcohol (PVA and/or polymethyl methacrylate (PMMA dielectrics is studied. Through analyzing the electrical characteristics of OFETs with various PVA/PMMA arrangements, it shows that charge, which is trapped in PVA bulk and at the interface of pentacene/PVA, is one of the origins of hysteresis. The results also show that memory window is proportional to both trap amount in PVA and charge density at the gate/PVA or PVA/pentacene interfaces. Hence, the controllable memory window of around 0 ∼ 10 V can be realized by controlling the thickness and combination of triple-layer polymer dielectrics.

  10. Hysteresis in conducting ferromagnets

    International Nuclear Information System (INIS)

    Schneider, Carl S.; Winchell, Stephen D.

    2006-01-01

    Maxwell's magnetic diffusion equation is solved for conducting ferromagnetic cylinders to predict a magnetic wave velocity, a time delay for flux penetration and an eddy current field, one of five fields in the linear unified field model of hysteresis. Measured Faraday voltages for a thin steel toroid are shown to be proportional to magnetic field step amplitude and decrease exponentially in time due to maximum rather than average permeability. Dynamic permeabilities are a field convolution of quasistatic permeability and the delay function from which we derive and observe square root dependence of coercivity on rate of field change

  11. OP09O-OP404-9 Wide Field Camera 3 CCD Quantum Efficiency Hysteresis

    Science.gov (United States)

    Collins, Nick

    2009-01-01

    The HST/Wide Field Camera (WFC) 3 UV/visible channel CCD detectors have exhibited an unanticipated quantum efficiency hysteresis (QEH) behavior. At the nominal operating temperature of -83C, the QEH feature contrast was typically 0.1-0.2% or less. The behavior was replicated using flight spare detectors. A visible light flat-field (540nm) with a several times full-well signal level can pin the detectors at both optical (600nm) and near-UV (230nm) wavelengths, suppressing the QEH behavior. We are characterizing the timescale for the detectors to become unpinned and developing a protocol for flashing the WFC3 CCDs with the instrument's internal calibration system in flight. The HST/Wide Field Camera 3 UV/visible channel CCD detectors have exhibited an unanticipated quantum efficiency hysteresis (QEH) behavior. The first observed manifestation of QEH was the presence in a small percentage of flat-field images of a bowtie-shaped contrast that spanned the width of each chip. At the nominal operating temperature of -83C, the contrast observed for this feature was typically 0.1-0.2% or less, though at warmer temperatures contrasts up to 5% (at -50C) have been observed. The bowtie morphology was replicated using flight spare detectors in tests at the GSFC Detector Characterization Laboratory by power cycling the detector while cold. Continued investigation revealed that a clearly-related global QE suppression at the approximately 5% level can be produced by cooling the detector in the dark; subsequent flat-field exposures at a constant illumination show asymptotically increasing response. This QE "pinning" can be achieved with a single high signal flat-field or a series of lower signal flats; a visible light (500-580nm) flat-field with a signal level of several hundred thousand electrons per pixel is sufficient for QE pinning at both optical (600nm) and near-UV (230nm) wavelengths. We are characterizing the timescale for the detectors to become unpinned and developing a

  12. Characterizing dynamic hysteresis and fractal statistics of chaotic two-phase flow and application to fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Burkholder, Michael B.; Litster, Shawn, E-mail: litster@andrew.cmu.edu [Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 (United States)

    2016-05-15

    In this study, we analyze the stability of two-phase flow regimes and their transitions using chaotic and fractal statistics, and we report new measurements of dynamic two-phase pressure drop hysteresis that is related to flow regime stability and channel water content. Two-phase flow dynamics are relevant to a variety of real-world systems, and quantifying transient two-phase flow phenomena is important for efficient design. We recorded two-phase (air and water) pressure drops and flow images in a microchannel under both steady and transient conditions. Using Lyapunov exponents and Hurst exponents to characterize the steady-state pressure fluctuations, we develop a new, measurable regime identification criteria based on the dynamic stability of the two-phase pressure signal. We also applied a new experimental technique by continuously cycling the air flow rate to study dynamic hysteresis in two-phase pressure drops, which is separate from steady-state hysteresis and can be used to understand two-phase flow development time scales. Using recorded images of the two-phase flow, we show that the capacitive dynamic hysteresis is related to channel water content and flow regime stability. The mixed-wettability microchannel and in-channel water introduction used in this study simulate a polymer electrolyte fuel cell cathode air flow channel.

  13. Structural transitions and hysteresis in clump- and stripe-forming systems under dynamic compression.

    Science.gov (United States)

    McDermott, Danielle; Olson Reichhardt, Cynthia J; Reichhardt, Charles

    2016-11-28

    Using numerical simulations, we study the dynamical evolution of particles interacting via competing long-range repulsion and short-range attraction in two dimensions. The particles are compressed using a time-dependent quasi-one dimensional trough potential that controls the local density, causing the system to undergo a series of structural phase transitions from a low density clump lattice to stripes, voids, and a high density uniform state. The compression proceeds via slow elastic motion that is interrupted with avalanche-like bursts of activity as the system collapses to progressively higher densities via plastic rearrangements. The plastic events vary in magnitude from small rearrangements of particles, including the formation of quadrupole-like defects, to large-scale vorticity and structural phase transitions. In the dense uniform phase, the system compresses through row reduction transitions mediated by a disorder-order process. We characterize the rearrangement events by measuring changes in the potential energy, the fraction of sixfold coordinated particles, the local density, and the velocity distribution. At high confinements, we find power law scaling of the velocity distribution during row reduction transitions. We observe hysteresis under a reversal of the compression when relatively few plastic rearrangements occur. The decompressing system exhibits distinct phase morphologies, and the phase transitions occur at lower compression forces as the system expands compared to when it is compressed.

  14. Reversible hysteresis inversion in MoS2 field effect transistors

    DEFF Research Database (Denmark)

    Kaushik, Naveen; Mackenzie, David M. A.; Thakar, Kartikey

    2017-01-01

    . The intrinsic-oxide trap model has been corroborated through device simulations. Further, pulsed current–voltage (I–V) measurements were carried out to extract the trap time constants at different temperatures. Non-volatile memory and temperature sensor applications exploiting temperature dependent hysteresis...

  15. Relaxation and optimisation of a phase-field control system with hysteresis

    Czech Academy of Sciences Publication Activity Database

    Krejčí, Pavel; Timoshin, S. A.; Tolstonogov, A. A.

    2018-01-01

    Roč. 91, č. 1 (2018), s. 85-100 ISSN 0020-7179 Institutional support: RVO:67985840 Keywords : evolution control system * hysteresis * state-dependent constraint Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 2.208, year: 2016 http:// www .tandfonline.com/doi/full/10.1080/00207179.2016.1268270

  16. Relaxation and optimisation of a phase-field control system with hysteresis

    Czech Academy of Sciences Publication Activity Database

    Krejčí, Pavel; Timoshin, S. A.; Tolstonogov, A. A.

    2018-01-01

    Roč. 91, č. 1 (2018), s. 85-100 ISSN 0020-7179 Institutional support: RVO:67985840 Keywords : evolution control system * hysteresis * state-dependent constraint Subject RIV: BA - General Mathematics OBOR OECD: Pure mathematics Impact factor: 2.208, year: 2016 http://www.tandfonline.com/doi/full/10.1080/00207179.2016.1268270

  17. Hysteresis behaviour of low-voltage organic field-effect transistors employing high dielectric constant polymer gate dielectrics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Se Hyun; Yun, Won Min; Kwon, Oh-Kwan; Hong, Kipyo; Yang, Chanwoo; Park, Chan Eon [POSTECH Organic Electronics Laboratory, Department of Chemical Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Choi, Woon-Seop, E-mail: cep@postech.ac.k, E-mail: wschoi@hoseo.ed [School of Display Engineering, Hoseo University, Asan City, Chungnam 336-795 (Korea, Republic of)

    2010-11-24

    Here, we report on the fabrication of low-voltage-operating pentacene-based organic field-effect transistors (OFETs) that utilize crosslinked cyanoethylated poly(vinyl alcohol) (CR-V) gate dielectrics. The crosslinked CR-V-based OFET could be operated successfully at low voltages (below 4 V), but abnormal behaviour during device operation, such as uncertainty in the field-effect mobility ({mu}) and hysteresis, was induced by the slow polarization of moieties embedded in the gate dielectric (e.g. polar functionalities, ionic impurities, water and solvent molecules). In an effort to improve the stability of OFET operation, we measured the dependence of {mu} and hysteresis on dielectric thickness, CR-V crosslinking conditions and sweep rate of the gate bias. The influence of the CR-V surface properties on {mu}, hysteresis, and the structural and morphological features of the pentacene layer grown on the gate dielectric was characterized and compared with the properties of pentacene grown on a polystyrene surface.

  18. Experimental evidence for dynamic friction on rock fractures from frequency-dependent nonlinear hysteresis and harmonic generation

    Science.gov (United States)

    Saltiel, Seth; Bonner, Brian P.; Mittal, Tushar; Delbridge, Brent; Ajo-Franklin, Jonathan B.

    2017-07-01

    Frictional properties affect the propagation of high-amplitude seismic waves across rock fractures and faults. Laboratory evidence suggests that these properties can be measured in active seismic surveys, potentially offering a route to characterizing friction in situ. We present experimental results from a subresonance torsional modulus and attenuation apparatus that utilizes micron-scale sinusoidal oscillations to probe the nonlinear stress-strain relation at a range of strain amplitudes and rates. Nonlinear effects are further quantified using harmonic distortion; however, time series data best illuminate underlying physical processes. The low-frequency stress-strain hysteretic loops show stiffening at the sinusoid's static ends, but stiffening is reduced above a threshold frequency. This shape is determined by harmonic generation in the strain; the stress signal has no harmonics, confirming that the fractured sample is the source of the nonlinearity. These qualitative observations suggest the presence of rate-dependent friction and are consistent between fractures in three different rock types. We propose that static friction at the low strain rate part of the cycle, when given sufficient "healing" time at low oscillation frequencies, causes this stiffening cusp shape in the hysteresis loop. While rate-and-state friction is commonly used to represent dynamic friction, it cannot capture static friction or negative slip velocities. So we implement another dynamic friction model, based on the work of Dahl, which describes this process and produces similar results. Since the two models have a similar form, parameterizations of field data could constraint fault model inputs, such as specific location velocity strengthening or weakening properties.

  19. Magnetic field hysteresis under various sweeping rates for Ni-Co-Mn-In metamagnetic shape memory alloys

    Science.gov (United States)

    Xu, Xiao; Kihara, Takumi; Tokunaga, Masashi; Matsuo, Akira; Ito, Wataru; Umetsu, Rie Y.; Kindo, Koichi; Kainuma, Ryosuke

    2013-09-01

    Magnetic field-induced transition of Ni45Co5Mn36.7In13.3 was investigated under magnetic fields with different sweeping rates. A static magnetic field produced by a superconducting magnet, a semi-static magnetic field created by a flywheel DC generator-powered magnet, and a pulsed magnetic field resulting from a condenser bank-powered magnet were used in this study, which covers sweeping rates of more than 6 orders. The magnetic field hysteresis is enlarged with increasing sweeping rate. The experimental results were consistent with a phenomenological model, and the activation energy for the thermally activated process was determined to be 0.7 eV for this alloy.

  20. Monte Carlo simulation of dynamic phase transitions and frequency dispersions of hysteresis curves in core/shell ferrimagnetic cubic nanoparticle

    Energy Technology Data Exchange (ETDEWEB)

    Vatansever, Erol, E-mail: erol.vatansever@deu.edu.tr

    2017-05-10

    By means of Monte Carlo simulation method with Metropolis algorithm, we elucidate the thermal and magnetic phase transition behaviors of a ferrimagnetic core/shell nanocubic system driven by a time dependent magnetic field. The particle core is composed of ferromagnetic spins, and it is surrounded by an antiferromagnetic shell. At the interface of the core/shell particle, we use antiferromagnetic spin–spin coupling. We simulate the nanoparticle using classical Heisenberg spins. After a detailed analysis, our Monte Carlo simulation results suggest that present system exhibits unusual and interesting magnetic behaviors. For example, at the relatively lower temperature regions, an increment in the amplitude of the external field destroys the antiferromagnetism in the shell part of the nanoparticle, leading to a ground state with ferromagnetic character. Moreover, particular attention has been dedicated to the hysteresis behaviors of the system. For the first time, we show that frequency dispersions can be categorized into three groups for a fixed temperature for finite core/shell systems, as in the case of the conventional bulk systems under the influence of an oscillating magnetic field. - Highlights: • Cubic core/shell nanoparticle is considered. • Monte-Carlo simulation with Metropolis algorithm is used. • The particle is subjected to time dependent oscillating magnetic field. • External field destroys the antiferromagnetism in the shell part of particle. • Frequency dispersions of hysteresis loop areas can be categorized into three groups.

  1. A mechanical brake hardware-in-the-loop simulation of a railway vehicle that accounts for hysteresis and pneumatic cylinder dynamics

    Directory of Open Access Journals (Sweden)

    Dong-Chan Lee

    2015-11-01

    Full Text Available A brake hardware-in-the-loop simulation system for a railway vehicle provides an effective platform for testing the braking performance under various dangerous braking conditions. However, in general, four-brake calipers are required to implement a mechanical brake system for one car. In this article, we implement a brake hardware-in-the-loop simulation system only with one brake caliper and three air tanks accounting for hysteresis and pneumatic cylinder dynamics, ultimately saving installation space and reducing financial budget costs. Since the brake caliper has a high nonlinearity, such as hysteresis resulting from friction and from the precompressed spring of the brake cylinder, we measured the hysteresis of the brake caliper clamping force for a mechanical brake system using loadcells, based on which a mathematical model was constructed for the hysteresis of the clamping force between the brake pad and the disk. Moreover, the pneumatic cylinder dynamics are identified and are implemented in three air tanks, together with hysteresis nonlinearity. The proposed brake hardware-in-the-loop simulation system is applied to the wheel-slide protection simulation of a railway vehicle with an initial speed of 80 km/h and demonstrated experimentally accounting for the hysteresis and brake cylinder dynamics.

  2. Quasiparticles in dynamical fields

    International Nuclear Information System (INIS)

    Donau, F.

    1986-01-01

    The equation of motion method provides the microscopic framework to describe quasi-particle excitations in odd-A transitional and deformed nuclei. The various modes of collective motion (i.e. rotations and fluctuations in the shape and pairing degrees of freedom) can be considered as external static and dynamical fields acting on the quasiparticles. Taking into account the self-consistency between the quasiparticle and the fields one can derive also the inertial properties without to introduce kinematical constraints. Inspecting the interacting bosom fermion approximation (IBFA) it is found that the pair field is not properly treated within this model. Footing on our microscope concept another type of boson fermion coupling model (BFM) is proposed. The role of the quadrople pairing is studied. It is suggested that the dynamics of the quadrupole pair field is of equal importance as that of the quadrupole distortion field

  3. Magnetic Hysteresis

    CERN Document Server

    Della Torre, Edward

    2000-01-01

    Understanding magnetic hysteresis is vitally important to the development of the science of magnetism as a whole and to the advancement of practical magnetic device applications. Magnetic Hysteresis, by acclaimed expert Edward Della Torre, presents a clear explanation of the connection between physical principles and phenomenological hysteresis. This comprehensive book offers a lucid analysis that enables the reader to save valuable time by reducing trial-and-error design. Dr. Della Torre uses physical principles to modify Preisach modeling and to describe the complex behavior of magnetic media. While Pretsach modeling is a useful mathematical tool, its congruency and deletion properties present limitations to accurate descriptions of magnetic materials. Step-by-step, this book describes the modifications that can overcome these limitations. Special attention is given to the use of feedback around a Preisach transducer to remove the congruency restriction, and to the use of accommodation and aftereffect model...

  4. Quantum hysteresis loops in microscopic system: The loop area as a ...

    Indian Academy of Sciences (India)

    possible use of hysteresis loop area in designing field parameters for optimal control is suggested. Keywords. Quantum hysteresis; stochastic resonance; quantum dynamics; Fourier grid methods; stochastically perturbed .... To calculate the integral on the right hand side, we need to know how m(t) varies over one cycle. The.

  5. Measurement of contact-angle hysteresis for droplets on nanopillared surface and in the Cassie and Wenzel states: a molecular dynamics simulation study.

    Science.gov (United States)

    Koishi, Takahiro; Yasuoka, Kenji; Fujikawa, Shigenori; Zeng, Xiao Cheng

    2011-09-27

    We perform large-scale molecular dynamics simulations to measure the contact-angle hysteresis for a nanodroplet of water placed on a nanopillared surface. The water droplet can be in either the Cassie state (droplet being on top of the nanopillared surface) or the Wenzel state (droplet being in contact with the bottom of nanopillar grooves). To measure the contact-angle hysteresis in a quantitative fashion, the molecular dynamics simulation is designed such that the number of water molecules in the droplets can be systematically varied, but the number of base nanopillars that are in direct contact with the droplets is fixed. We find that the contact-angle hysteresis for the droplet in the Cassie state is weaker than that in the Wenzel state. This conclusion is consistent with the experimental observation. We also test a different definition of the contact-angle hysteresis, which can be extended to estimate hysteresis between the Cassie and Wenzel state. The idea is motivated from the appearance of the hysteresis loop typically seen in computer simulation of the first-order phase transition, which stems from the metastability of a system in different thermodynamic states. Since the initial shape of the droplet can be controlled arbitrarily in the computer simulation, the number of base nanopillars that are in contact with the droplet can be controlled as well. We show that the measured contact-angle hysteresis according to the second definition is indeed very sensitive to the initial shape of the droplet. Nevertheless, the contact-angle hystereses measured based on the conventional and new definition seem converging in the large droplet limit. © 2011 American Chemical Society

  6. Nonlinear dynamic analysis of periodic ferroresonance based on a novel hysteresis approach

    Science.gov (United States)

    Zou, Mi; Sima, Wen-Xia; Yang, Ming; Yang, Qing; Li, Licheng; Li, Jianbiao

    2016-03-01

    Ferroresonance is one of the most harmful and longest known power quality disturbances in the history of AC power systems. The ability of predicting transient and steady-state ferroresonance simulations mainly depends on the accuracy of the power transformer model. Most existing voltage transformer models apply single-valued nonlinear functions to represent the core nonlinearities. This study, based on our previous work, proposes a newly improved and accurate transformer iron core hysteresis model for ferroresonance simulation by extension of the classical arctangent model. To verify the proposed model’s accuracy and superiority, three different ferroresonant voltage and current waveform simulations were performed using both the proposed model and renowned EMTP Type-96 model under the same system parameters. In addition, simulation results were compared with the corresponding experimental measurements. The results indicate that the proposed model is easily implemented using numerical modeling method with good stability and convergence, and is sufficiently accurate for both transient and steady-state periodic ferroresonance analysis.

  7. Domain patterns and hysteresis in phase-transforming solids: analysis and numerical simulations of a sharp interface dissipative model via phase-field approximation

    Czech Academy of Sciences Publication Activity Database

    DeSimone, A.; Kružík, Martin

    2013-01-01

    Roč. 8, č. 2 (2013), s. 481-499 ISSN 1556-1801 R&D Projects: GA ČR(CZ) GAP201/12/0671 Institutional support: RVO:67985556 Keywords : hysteresis * shape memory Subject RIV: BA - General Mathematics Impact factor: 0.952, year: 2013 http://library.utia.cas.cz/separaty/2013/MTR/kruzik-domain patterns and hysteresis in phase-transforming solids analysis and numerical simulations of a sharp interface dissipative model via phase-field approximation.pdf

  8. Describing the efect of tempering on hysteresis curves of 54SiCr6 spring steel by the effective field model

    Czech Academy of Sciences Publication Activity Database

    Perevertov, Oleksiy

    2012-01-01

    Roč. 324, č. 8 (2012), s. 1645-1648 ISSN 0304-8853 Grant - others:GA AV ČR(CZ) M100100906 Institutional research plan: CEZ:AV0Z10100520 Keywords : hysteresis curve * internal stress * tempering * spring steel * effective field model * coincidence point Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.826, year: 2012

  9. Effect of the Hamiltonian parameters on the hysteresis properties of the kinetic mixed spin (1/2, 1) Ising ferrimagnetic model on a hexagonal lattice

    Energy Technology Data Exchange (ETDEWEB)

    Batı, Mehmet, E-mail: mehmet.bati@erdogan.edu.tr [Department of Physics, Recep Tayyip Erdoğan University, 53100 Rize (Turkey); Ertaş, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2017-05-15

    The hysteresis properties of a kinetic mixed spin (1/2, 1) Ising ferrimagnetic system on a hexagonal lattice are studied by means of the dynamic mean field theory. In the present study, the effects of the nearest-neighbor interaction, temperature, frequency of oscillating magnetic field and the exchange anisotropy on the hysteresis properties of the kinetic system are discussed in detail. A number of interesting phenomena such as the shape of hysteresis loops with one, two, three and inverted-hysteresis/proteresis (butterfly shape hysteresis) have been obtained. Finally, the obtained results are compared with some experimental and theoretical results and a qualitatively good agreement is found.

  10. Magnetic field computation in a non-oriented sheet cross-section considering the hysteresis phenomenon

    Energy Technology Data Exchange (ETDEWEB)

    Boukhtache, Sebti, E-mail: sebti_boukhtache@yahoo.f [Laboratoire d' Electrotechnique de Batna, Rue Chahid Med Boukhlouf, University of Batna, 05000 Batna (Algeria); Yakhlef, Malika, E-mail: malika_yakhlef@yahoo.f [Laboratoire d' Electrotechnique de Batna, Rue Chahid Med Boukhlouf, University of Batna, 05000 Batna (Algeria); Chabane, Mabrouk, E-mail: machabane@yahoo.co [Laboratoire d' Electrotechnique de Batna, Rue Chahid Med Boukhlouf, University of Batna, 05000 Batna (Algeria)

    2010-03-15

    The aim of the present work is the numerical computation of the average magnetic induction in the cross-section of a non-oriented 3% Si-Fe sheet by solving the magnetic diffusion equation. Jiles' dynamic model is used to describe the magnetization law. The obtained results are compared with those of the measurements carried out for frequencies of 0.5, 50, 200 and 500 Hz. A satisfactory agreement is obtained between both types of results.

  11. Hydrophobic dielectric surface influenced active layer thickness effect on hysteresis and mobility degradation in organic field effect transistors

    Science.gov (United States)

    Padma, N.

    2016-02-01

    Effect of active layer thickness, influenced by the hydrophobic dielectric surface, on the performance of copper phthalocyanine based organic field effect transistors (OFETs) was studied. While charge carrier mobility was found to be highest for an optimum thickness of 30 nm, hysteresis and threshold voltage shift were found to be minimum for 15 nm thick film which is attributed to the excess availability of photogenerated carriers, especially close to the dielectric/semiconductor interface, as this thickness is within the exciton quenching length in organic semiconductors. But prolonged bias stress resulted in larger decay in drain current for higher thickness indicating the dominant role played by the larger grain boundary density in the increased volume. These results were found to be different from that on unmodified SiO2 dielectric with higher surface energy and were suggested to be caused by the 3D growth mode of CuPc films on the hydrophobic surface. Mobility degradation at higher gate voltages also exhibited a dependence on the active layer thickness which was tuned by the hydrophobic surface induced growth mode at the dielectric/semiconductor interface.

  12. Lévy stable noise-induced transitions: stochastic resonance, resonant activation and dynamic hysteresis

    International Nuclear Information System (INIS)

    Dybiec, Bartłomiej; Gudowska-Nowak, Ewa

    2009-01-01

    A standard approach to analysis of noise-induced effects in stochastic dynamics assumes a Gaussian character of the noise term describing interaction of the analyzed system with its complex surroundings. An additional assumption about the existence of timescale separation between the dynamics of the measured observable and the typical timescale of the noise allows external fluctuations to be modeled as temporally uncorrelated and therefore white. However, in many natural phenomena the assumptions concerning the above mentioned properties of 'Gaussianity' and 'whiteness' of the noise can be violated. In this context, in contrast to the spatiotemporal coupling characterizing general forms of non-Markovian or semi-Markovian Lévy walks, so called Lévy flights correspond to the class of Markov processes which can still be interpreted as white, but distributed according to a more general, infinitely divisible, stable and non-Gaussian law. Lévy noise-driven non-equilibrium systems are known to manifest interesting physical properties and have been addressed in various scenarios of physical transport exhibiting a superdiffusive behavior. Here we present a brief overview of our recent investigations aimed at understanding features of stochastic dynamics under the influence of Lévy white noise perturbations. We find that the archetypal phenomena of noise-induced ordering are robust and can be detected also in systems driven by memoryless, non-Gaussian, heavy-tailed fluctuations with infinite variance

  13. Hysteresis, reentrance, and glassy dynamics in systems of self-propelled rods.

    Science.gov (United States)

    Kuan, Hui-Shun; Blackwell, Robert; Hough, Loren E; Glaser, Matthew A; Betterton, M D

    2015-01-01

    Nonequilibrium active matter made up of self-driven particles with short-range repulsive interactions is a useful minimal system to study active matter as the system exhibits collective motion and nonequilibrium order-disorder transitions. We studied high-aspect-ratio self-propelled rods over a wide range of packing fractions and driving to determine the nonequilibrium state diagram and dynamic properties. Flocking and nematic-laning states occupy much of the parameter space. In the flocking state, the average internal pressure is high and structural and mechanical relaxation times are long, suggesting that rods in flocks are in a translating glassy state despite overall flock motion. In contrast, the nematic-laning state shows fluidlike behavior. The flocking state occupies regions of the state diagram at both low and high packing fraction separated by nematic-laning at low driving and a history-dependent region at higher driving; the nematic-laning state transitions to the flocking state for both compression and expansion. We propose that the laning-flocking transitions are a type of glass transition that, in contrast to other glass-forming systems, can show fluidization as density increases. The fluid internal dynamics and ballistic transport of the nematic-laning state may promote collective dynamics of rod-shaped micro-organisms.

  14. Dynamic phase diagrams of the Ising metamagnet in an oscillating magnetic field within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.t [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2010-07-12

    Dynamic aspects of a two-sublattice Ising metamagnet on honeycomb, square and hexagonal lattices under the presence of a time-dependent oscillating external magnetic field are studied by using the effective-field theory with correlations. The set of effective-field dynamic equations is derived by employing Glauber transition rates. The phases in the system are obtained by solving these dynamic equations. The thermal behavior of the dynamic staggered magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. The phase diagrams are constructed in two different planes, and exhibit dynamic tricritical behavior, which strongly depends on interaction parameters. In order to investigate the spin correlation effect on the dynamic phase diagrams of the system, the results are also given within the framework of the dynamic mean-field approximation.

  15. Dynamic phase diagrams of the Ising metamagnet in an oscillating magnetic field within the effective-field theory

    International Nuclear Information System (INIS)

    Deviren, Bayram; Keskin, Mustafa

    2010-01-01

    Dynamic aspects of a two-sublattice Ising metamagnet on honeycomb, square and hexagonal lattices under the presence of a time-dependent oscillating external magnetic field are studied by using the effective-field theory with correlations. The set of effective-field dynamic equations is derived by employing Glauber transition rates. The phases in the system are obtained by solving these dynamic equations. The thermal behavior of the dynamic staggered magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. The phase diagrams are constructed in two different planes, and exhibit dynamic tricritical behavior, which strongly depends on interaction parameters. In order to investigate the spin correlation effect on the dynamic phase diagrams of the system, the results are also given within the framework of the dynamic mean-field approximation.

  16. A mechanical brake hardware-in-the-loop simulation of a railway vehicle that accounts for hysteresis and pneumatic cylinder dynamics

    OpenAIRE

    Dong-Chan Lee; Chul-Goo Kang

    2015-01-01

    A brake hardware-in-the-loop simulation system for a railway vehicle provides an effective platform for testing the braking performance under various dangerous braking conditions. However, in general, four-brake calipers are required to implement a mechanical brake system for one car. In this article, we implement a brake hardware-in-the-loop simulation system only with one brake caliper and three air tanks accounting for hysteresis and pneumatic cylinder dynamics, ultimately saving installat...

  17. Hysteretic dynamics of active particles in a periodic orienting field.

    Science.gov (United States)

    Romensky, Maksym; Scholz, Dimitri; Lobaskin, Vladimir

    2015-07-06

    Active motion of living organisms and artificial self-propelling particles has been an area of intense research at the interface of biology, chemistry and physics. Significant progress in understanding these phenomena has been related to the observation that dynamic self-organization in active systems has much in common with ordering in equilibrium condensed matter such as spontaneous magnetization in ferromagnets. The velocities of active particles may behave similar to magnetic dipoles and develop global alignment, although interactions between the individuals might be completely different. In this work, we show that the dynamics of active particles in external fields can also be described in a way that resembles equilibrium condensed matter. It follows simple general laws, which are independent of the microscopic details of the system. The dynamics is revealed through hysteresis of the mean velocity of active particles subjected to a periodic orienting field. The hysteresis is measured in computer simulations and experiments on unicellular organisms. We find that the ability of the particles to follow the field scales with the ratio of the field variation period to the particles' orientational relaxation time, which, in turn, is related to the particle self-propulsion power and the energy dissipation rate. The collective behaviour of the particles due to aligning interactions manifests itself at low frequencies via increased persistence of the swarm motion when compared with motion of an individual. By contrast, at high field frequencies, the active group fails to develop the alignment and tends to behave like a set of independent individuals even in the presence of interactions. We also report on asymptotic laws for the hysteretic dynamics of active particles, which resemble those in magnetic systems. The generality of the assumptions in the underlying model suggests that the observed laws might apply to a variety of dynamic phenomena from the motion of

  18. Hysteresis modelling of GO laminations for arbitrary in-plane directions taking into account the dynamics of orthogonal domain walls

    Energy Technology Data Exchange (ETDEWEB)

    Baghel, A.P.S.; Sai Ram, B. [Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India); Chwastek, K. [Department of Electrical Engineering Czestochowa University of Technology (Poland); Daniel, L. [Group of Electrical Engineering-Paris (GeePs), CNRS(UMR8507)/CentraleSupelec/UPMC/Univ Paris-Sud, 11 rue Joliot-Curie, 91192 Gif-sur-Yvette (France); Kulkarni, S.V. [Department of Electrical Engineering, Indian Institute of Technology Bombay, Mumbai 400076 (India)

    2016-11-15

    The anisotropy of magnetic properties in grain-oriented steels is related to their microstructure. It results from the anisotropy of the single crystal properties combined to crystallographic texture. The magnetization process along arbitrary directions can be explained using phase equilibrium for domain patterns, which can be described using Neel's phase theory. According to the theory the fractions of 180° and 90° domain walls depend on the direction of magnetization. This paper presents an approach to model hysteresis loops of grain-oriented steels along arbitrary in-plane directions. The considered description is based on a modification of the Jiles–Atherton model. It includes a modified expression for the anhysteretic magnetization which takes into account contributions of two types of domain walls. The computed hysteresis curves for different directions are in good agreement with experimental results. - Highlights: • An extended Jiles–Atherton description is used to model hysteresis loops in GO steels. • The model stresses the role of material anisotropy and different contributions of the two types of domain walls. • Hysteresis loops can be modeled along arbitrary in-plane directions. • Modeling results are in good agreement with experiments.

  19. Vacuum in thermo field dynamics

    International Nuclear Information System (INIS)

    Matsumoto, H.

    1987-01-01

    The framework for thermo field dynamics is presented in the axiomatic form. It consists of the conditions for the quantum algebra and the conditions for the vacuum. Choices of nonequilibrium vacuums correspond to nonequilibrium phenomena. (orig.)

  20. Vector hysteresis models

    Czech Academy of Sciences Publication Activity Database

    Krejčí, Pavel

    1991-01-01

    Roč. 2, - (1991), s. 281-292 ISSN 0956-7925 Keywords : vector hysteresis operator * hysteresis potential * differential inequality Subject RIV: BA - General Mathematics http://www.math.cas.cz/~krejci/b15p.pdf

  1. Atom dynamics in laser fields

    International Nuclear Information System (INIS)

    Jang, Su; Mi, No Gin

    2004-12-01

    This book introduces coherent dynamics of internal state, spread of atoms wave speed, semiclassical atoms density matrix such as dynamics equation in both still and moving atoms, excitation of atoms in movement by light, dipole radiating power, quantum statistical mechanics by atoms in movement, semiclassical atoms in movement, atoms in movement in the uniform magnetic field including effects of uniform magnetic field, atom cooling using laser such as Doppler cooling, atom traps using laser and mirrors, radiant heat which particles receive, and near field interactions among atoms in laser light.

  2. Dynamic phase transitions in a cylindrical Ising nanowire under a time-dependent oscillating magnetic field

    International Nuclear Information System (INIS)

    Deviren, Bayram; Kantar, Ersin; Keskin, Mustafa

    2012-01-01

    The dynamic phase transitions in a cylindrical Ising nanowire system under a time-dependent oscillating external magnetic field for both ferromagnetic and antiferromagnetic interactions are investigated within the effective-field theory with correlations and the Glauber-type stochastic dynamics approach. The effective-field dynamic equations for the average longitudinal magnetizations on the surface shell and core are derived by employing the Glauber transition rates. Temperature dependence of the dynamic magnetizations, the dynamic total magnetization, the hysteresis loop areas and the dynamic correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, five different types of compensation behaviors in the Néel classification nomenclature exist in the system. The system also exhibits a reentrant behavior. - Highlights: ► The dynamic aspects of a cylindrical Ising nanowire are investigated in detail. ► The dynamic magnetizations, hysteresis loop areas and correlations are calculated. ► We studied both the FM and AFM interactions within the EFT with correlations. ► Some characteristic phenomena are found depending on the interaction parameters. ► We obtained five different types of compensation behaviors and reentrant behavior.

  3. Dynamic phase transitions in a cylindrical Ising nanowire under a time-dependent oscillating magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Kantar, Ersin [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-07-15

    The dynamic phase transitions in a cylindrical Ising nanowire system under a time-dependent oscillating external magnetic field for both ferromagnetic and antiferromagnetic interactions are investigated within the effective-field theory with correlations and the Glauber-type stochastic dynamics approach. The effective-field dynamic equations for the average longitudinal magnetizations on the surface shell and core are derived by employing the Glauber transition rates. Temperature dependence of the dynamic magnetizations, the dynamic total magnetization, the hysteresis loop areas and the dynamic correlations are investigated in order to characterize the nature (first- or second-order) of the dynamic transitions as well as the dynamic phase transition temperatures and the compensation behaviors. The system strongly affected by the surface situations. Some characteristic phenomena are found depending on the ratio of the physical parameters in the surface shell and the core. According to the values of Hamiltonian parameters, five different types of compensation behaviors in the Neel classification nomenclature exist in the system. The system also exhibits a reentrant behavior. - Highlights: Black-Right-Pointing-Pointer The dynamic aspects of a cylindrical Ising nanowire are investigated in detail. Black-Right-Pointing-Pointer The dynamic magnetizations, hysteresis loop areas and correlations are calculated. Black-Right-Pointing-Pointer We studied both the FM and AFM interactions within the EFT with correlations. Black-Right-Pointing-Pointer Some characteristic phenomena are found depending on the interaction parameters. Black-Right-Pointing-Pointer We obtained five different types of compensation behaviors and reentrant behavior.

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

    Energy Technology Data Exchange (ETDEWEB)

    Boukheddaden, Kamel, E-mail: kbo@physique.uvsq.fr [GEMaC, Université de Versailles St-Quentin, 45 Avenue des Etats Unis, 78035 Versailles (France); Sy, Mouhamadou; Paez-Espejo, Miguel [GEMaC, Université de Versailles St-Quentin, 45 Avenue des Etats Unis, 78035 Versailles (France); Slimani, Ahmed [Laboratoire des matériaux ferroélectriques, Département de Physique, Faculté des Sciences de Sfax, Route de la Soukra km 3.5 BP 1171, 3018 Sfax (Tunisia); Varret, François [GEMaC, Université de Versailles St-Quentin, 45 Avenue des Etats Unis, 78035 Versailles (France)

    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}{sub 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.

  5. Field-effect transistors with high mobility and small hysteresis of transfer characteristics based on CH3NH3PbBr3 films

    Science.gov (United States)

    Aleshin, A. N.; Shcherbakov, I. P.; Trapeznikova, I. N.; Petrov, V. N.

    2017-12-01

    Field-effect transistor (FET) structures based on soluble organometallic perovskites, CH3NH3PbBr3, were obtained and their electrical properties were studied. FETs made of CH3NH3PbBr3 films possess current- voltage characteristics (IVs) typical for ambipolar FETs with saturation regime. The transfer characteristics of FETs based on CH3NH3PbBr3 have an insignificant hysteresis and slightly depend on voltage at the source-drain. Mobilities of charge carriers (holes) calculated from IVs of FETs based on CH3NH3PbBr3 at 300 K in saturation and weak field regimes were 5 and 2 cm2/V s, respectively, whereas electron mobility is 3 cm2/V s, which exceeds the mobility value 1 cm2/V s obtained earlier for FETs based on CH3NH3PbI3.

  6. Excitation thresholds of field-aligned irregularities and associated ionospheric hysteresis at very high latitudes observed using SPEAR-induced HF radar backscatter

    Directory of Open Access Journals (Sweden)

    D. M. Wright

    2009-07-01

    Full Text Available On 10 October 2006 the SPEAR high power radar facility was operated in a power-stepping mode where both CUTLASS radars were detecting backscatter from the SPEAR-induced field-aligned irregularities (FAIs. The effective radiated power of SPEAR was varied from 1–10 MW. The aim of the experiment was to investigate the power thresholds for excitation (Pt and collapse (Pc of artificially-induced FAIs in the ionosphere over Svalbard. It was demonstrated that FAI could be excited by a SPEAR ERP of only 1 MW, representing only 1/30th of SPEAR's total capability, and that once created the irregularities could be maintained for even lower powers. The experiment also demonstrated that the very high latitude ionosphere exhibits hysteresis, where the down-going part of the power cycle provided a higher density of irregularities than for the equivalent part of the up-going cycle. Although this second result is similar to that observed previously by CUTLASS in conjunction with the Tromsø heater, the same is not true for the equivalent incoherent scatter measurements. The EISCAT Svalbard Radar (ESR failed to detect any hysteresis in the plasma parameters over Svalbard in stark contract with the measurements made using the Tromsø UHF.

  7. Turbulence via information field dynamics

    Science.gov (United States)

    Ensslin, Torsten A.

    2015-08-01

    Turbulent flows exhibit-scale free regimes, for which information on the statistical properties of the dynamics exists for many length-scales. The simulation of turbulent systems can benefit from the inclusion of such information on sub-grid process. How can statistical information about the flow on small scales be optimally be incorporated into simulation schemes? Information field dynamics (IFD) is a novel information theoretical framework to design schemes that exploit such statistical knowledge on sub-grid flow fluctuations. In this talk, I will introduce the basic idea of IFD, present its first toy applications, and discuss the next steps towards its usage in complex turbulence simulations.

  8. Rotation of Magnetization Derived from Brownian Relaxation in Magnetic Fluids of Different Viscosity Evaluated by Dynamic Hysteresis Measurements over a Wide Frequency Range.

    Science.gov (United States)

    Ota, Satoshi; Kitaguchi, Ryoichi; Takeda, Ryoji; Yamada, Tsutomu; Takemura, Yasushi

    2016-09-10

    The dependence of magnetic relaxation on particle parameters, such as the size and anisotropy, has been conventionally discussed. In addition, the influences of external conditions, such as the intensity and frequency of the applied field, the surrounding viscosity, and the temperature on the magnetic relaxation have been researched. According to one of the basic theories regarding magnetic relaxation, the faster type of relaxation dominates the process. However, in this study, we reveal that Brownian and Néel relaxations coexist and that Brownian relaxation can occur after Néel relaxation despite having a longer relaxation time. To understand the mechanisms of Brownian rotation, alternating current (AC) hysteresis loops were measured in magnetic fluids of different viscosities. These loops conveyed the amplitude and phase delay of the magnetization. In addition, the intrinsic loss power (ILP) was calculated using the area of the AC hysteresis loops. The ILP also showed the magnetization response regarding the magnetic relaxation over a wide frequency range. To develop biomedical applications of magnetic nanoparticles, such as hyperthermia and magnetic particle imaging, it is necessary to understand the mechanisms of magnetic relaxation.

  9. Rotation of Magnetization Derived from Brownian Relaxation in Magnetic Fluids of Different Viscosity Evaluated by Dynamic Hysteresis Measurements over a Wide Frequency Range

    Directory of Open Access Journals (Sweden)

    Satoshi Ota

    2016-09-01

    Full Text Available The dependence of magnetic relaxation on particle parameters, such as the size and anisotropy, has been conventionally discussed. In addition, the influences of external conditions, such as the intensity and frequency of the applied field, the surrounding viscosity, and the temperature on the magnetic relaxation have been researched. According to one of the basic theories regarding magnetic relaxation, the faster type of relaxation dominates the process. However, in this study, we reveal that Brownian and Néel relaxations coexist and that Brownian relaxation can occur after Néel relaxation despite having a longer relaxation time. To understand the mechanisms of Brownian rotation, alternating current (AC hysteresis loops were measured in magnetic fluids of different viscosities. These loops conveyed the amplitude and phase delay of the magnetization. In addition, the intrinsic loss power (ILP was calculated using the area of the AC hysteresis loops. The ILP also showed the magnetization response regarding the magnetic relaxation over a wide frequency range. To develop biomedical applications of magnetic nanoparticles, such as hyperthermia and magnetic particle imaging, it is necessary to understand the mechanisms of magnetic relaxation.

  10. Improved hysteresis in a normally-off AlGaN/GaN MOS heterojunction field-effect transistor with a recessed gate structure formed by selective regrowth

    Science.gov (United States)

    Nakazawa, Satoshi; Shiozaki, Nanako; Negoro, Noboru; Tsurumi, Naohiro; Anda, Yoshiharu; Ishida, Masahiro; Ueda, Tetsuzo

    2017-09-01

    A normally-off AlGaN/GaN MOS heterojunction field-effect transistor (MOS-HFET) with a recessed gate structure formed by selective area regrowth is demonstrated. The fabricated MOS-HFET exhibits a threshold voltage of 1.7 V with an improved hysteresis of 0.5 V as compared with a device fabricated by a conventional dry etching process. An analysis of capacitance-voltage (C-V) characteristics reveals that the dry etching process increases interface state density and introduces an additional discrete trap. The use of the selective area regrowth technique effectively suppresses such degradation, avoiding the MOS interface from being exposed to dry etching. The results presented in this paper indicate that the selective area regrowth technique is promising for the fabrication of normally-off AlGaN/GaN MOS-HFETs.

  11. Temperature dependent piezoelectric response and strain-electric-field hysteresis of rare-earth modified bismuth ferrite ceramics

    DEFF Research Database (Denmark)

    Walker, Julian; Ursic, Hana; Bencan, Andreja

    2016-01-01

    The rare-earth (RE)-modified bismuth ferrite (BiFeO3 or BFO) family of ferroelectrics have uncomplicated lead-free chemistries and simple perovskite structures. Due to the high Curie transition temperature of the parent BiFeO3 perovskite (similar to 830 °C), they are promising piezoelectric...... materials for use at elevated temperatures. However, the influence of the specific RE species on the electromechanical behavior at high temperatures and above the coercive electric-field is not widely reported. Here, structural analysis over multiple length scales using X-ray diffraction, transmission......, there are qualitative differences in the field-induced strain and electric current behavior as a function of electric-field cycling and the materials exhibit an electrical-history dependent behavior. Bi0.91Dy0.09FeO3 possesses an improved d33 stability as a function of temperature relative to the parent BFO perovskite...

  12. Dynamic phase transitions and dynamic phase diagrams in the kinetic spin-5/2 Blume–Capel model in an oscillating external magnetic field: Effective-field theory and the Glauber-type stochastic dynamics approach

    International Nuclear Information System (INIS)

    Ertaş, Mehmet; Keskin, Mustafa; Deviren, Bayram

    2012-01-01

    Using an effective field theory with correlations, we study a kinetic spin-5/2 Blume–Capel model with bilinear exchange interaction and single-ion crystal field on a square lattice. The effective-field dynamic equation is derived by employing the Glauber transition rates. First, the phases in the kinetic system are obtained by solving this dynamic equation. Then, the thermal behavior of the dynamic magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. Finally, we present the phase diagrams in two planes, namely (T/zJ, h 0 /zJ) and (T/zJ, D/zJ), where T absolute temperature, h 0 , the amplitude of the oscillating field, D, crystal field interaction or single-ion anisotropy constant and z denotes the nearest-neighbor sites of the central site. The phase diagrams exhibit four fundamental phases and ten mixed phases which are composed of binary, ternary and tetrad combination of fundamental phases, depending on the crystal field interaction parameter. Moreover, the phase diagrams contain a dynamic tricritical point (T), a double critical end point (B), a multicritical point (A) and zero-temperature critical point (Z). - Highlights: ► The effective-field theory is used to study the kinetic spin-5/2 Ising Blume–Capel model. ► Time variations of average order parameter have been studied to find phases in the system. ► The dynamic magnetization, hysteresis loop area and correlation have been calculated. ► The dynamic phase boundaries of the system depend on D/zJ. ► The dynamic phase diagrams are presented in the (T/zJ, h 0 /zJ) and (D/zJ, T/zJ) planes.

  13. Dynamic phase transitions and dynamic phase diagrams in the kinetic spin-5/2 Blume-Capel model in an oscillating external magnetic field: Effective-field theory and the Glauber-type stochastic dynamics approach

    Energy Technology Data Exchange (ETDEWEB)

    Ertas, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey)

    2012-04-15

    Using an effective field theory with correlations, we study a kinetic spin-5/2 Blume-Capel model with bilinear exchange interaction and single-ion crystal field on a square lattice. The effective-field dynamic equation is derived by employing the Glauber transition rates. First, the phases in the kinetic system are obtained by solving this dynamic equation. Then, the thermal behavior of the dynamic magnetization, the hysteresis loop area and correlation are investigated in order to characterize the nature of the dynamic transitions and to obtain dynamic phase transition temperatures. Finally, we present the phase diagrams in two planes, namely (T/zJ, h{sub 0}/zJ) and (T/zJ, D/zJ), where T absolute temperature, h{sub 0}, the amplitude of the oscillating field, D, crystal field interaction or single-ion anisotropy constant and z denotes the nearest-neighbor sites of the central site. The phase diagrams exhibit four fundamental phases and ten mixed phases which are composed of binary, ternary and tetrad combination of fundamental phases, depending on the crystal field interaction parameter. Moreover, the phase diagrams contain a dynamic tricritical point (T), a double critical end point (B), a multicritical point (A) and zero-temperature critical point (Z). - Highlights: Black-Right-Pointing-Pointer The effective-field theory is used to study the kinetic spin-5/2 Ising Blume-Capel model. Black-Right-Pointing-Pointer Time variations of average order parameter have been studied to find phases in the system. Black-Right-Pointing-Pointer The dynamic magnetization, hysteresis loop area and correlation have been calculated. Black-Right-Pointing-Pointer The dynamic phase boundaries of the system depend on D/zJ. Black-Right-Pointing-Pointer The dynamic phase diagrams are presented in the (T/zJ, h{sub 0}/zJ) and (D/zJ, T/zJ) planes.

  14. Static and dynamical Meissner force fields

    Science.gov (United States)

    Weinberger, B. R.; Lynds, L.; Hull, J. R.; Mulcahy, T. M.

    1991-01-01

    The coupling between copper-based high temperature superconductors (HTS) and magnets is represented by a force field. Zero-field cooled experiments were performed with several forms of superconductors: 1) cold-pressed sintered cylindrical disks; 2) small particles fixed in epoxy polymers; and 3) small particles suspended in hydrocarbon waxes. Using magnets with axial field symmetries, direct spatial force measurements in the range of 0.1 to 10(exp 4) dynes were performed with an analytical balance and force constants were obtained from mechanical vibrational resonances. Force constants increase dramatically with decreasing spatial displacement. The force field displays a strong temperature dependence between 20 and 90 K and decreases exponentially with increasing distance of separation. Distinct slope changes suggest the presence of B-field and temperature-activated processes that define the forces. Hysteresis measurements indicated that the magnitude of force scales roughly with the volume fraction of HTS in composite structures. Thus, the net force resulting from the field interaction appears to arise from regions as small or smaller than the grain size and does not depend on contiguous electron transport over large areas. Results of these experiments are discussed.

  15. Understanding Unemployment Hysteresis

    DEFF Research Database (Denmark)

    Møller, Niels Framroze

    What explains the persistence of unemployment? The literature on hysteresis, which is based on unit root testing in autoregressive models, consists of a vast number of univariate studies, i.e. that analyze unemployment series in isolation, but few multivariate analyses that focus on the sources o...... by the hysteresis theories. Instead, it is the equilibrium that has evolved persistently as a consequence of exogenous oil prices shifting the price setting relation (in the unemployment-real wage space) in a non-stationary manner....... changing equilibrium, slow adjustment towards the equilibrium (persistent ‡fluctuations), or perhaps even a combination of the two. Different hypotheses of slow adjustment, as implied by theories of hysteresis, nominal rigidities or labor hoarding can also be compared. A small illustrative application...

  16. Hysteresis in layered spring magnets.

    Energy Technology Data Exchange (ETDEWEB)

    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.

  17. Molecular magnetic hysteresis at 60 kelvin in dysprosocenium.

    Science.gov (United States)

    Goodwin, Conrad A P; Ortu, Fabrizio; Reta, Daniel; Chilton, Nicholas F; Mills, David P

    2017-08-23

    Lanthanides have been investigated extensively for potential applications in quantum information processing and high-density data storage at the molecular and atomic scale. Experimental achievements include reading and manipulating single nuclear spins, exploiting atomic clock transitions for robust qubits and, most recently, magnetic data storage in single atoms. Single-molecule magnets exhibit magnetic hysteresis of molecular origin-a magnetic memory effect and a prerequisite of data storage-and so far lanthanide examples have exhibited this phenomenon at the highest temperatures. However, in the nearly 25 years since the discovery of single-molecule magnets, hysteresis temperatures have increased from 4 kelvin to only about 14 kelvin using a consistent magnetic field sweep rate of about 20 oersted per second, although higher temperatures have been achieved by using very fast sweep rates (for example, 30 kelvin with 200 oersted per second). Here we report a hexa-tert-butyldysprosocenium complex-[Dy(Cp ttt ) 2 ][B(C 6 F 5 ) 4 ], with Cp ttt  = {C 5 H 2 t Bu 3 -1,2,4} and t Bu = C(CH 3 ) 3 -which exhibits magnetic hysteresis at temperatures of up to 60 kelvin at a sweep rate of 22 oersted per second. We observe a clear change in the relaxation dynamics at this temperature, which persists in magnetically diluted samples, suggesting that the origin of the hysteresis is the localized metal-ligand vibrational modes that are unique to dysprosocenium. Ab initio calculations of spin dynamics demonstrate that magnetic relaxation at high temperatures is due to local molecular vibrations. These results indicate that, with judicious molecular design, magnetic data storage in single molecules at temperatures above liquid nitrogen should be possible.

  18. Molecular magnetic hysteresis at 60 kelvin in dysprosocenium

    Science.gov (United States)

    Goodwin, Conrad A. P.; Ortu, Fabrizio; Reta, Daniel; Chilton, Nicholas F.; Mills, David P.

    2017-08-01

    Lanthanides have been investigated extensively for potential applications in quantum information processing and high-density data storage at the molecular and atomic scale. Experimental achievements include reading and manipulating single nuclear spins, exploiting atomic clock transitions for robust qubits and, most recently, magnetic data storage in single atoms. Single-molecule magnets exhibit magnetic hysteresis of molecular origin—a magnetic memory effect and a prerequisite of data storage—and so far lanthanide examples have exhibited this phenomenon at the highest temperatures. However, in the nearly 25 years since the discovery of single-molecule magnets, hysteresis temperatures have increased from 4 kelvin to only about 14 kelvin using a consistent magnetic field sweep rate of about 20 oersted per second, although higher temperatures have been achieved by using very fast sweep rates (for example, 30 kelvin with 200 oersted per second). Here we report a hexa-tert-butyldysprosocenium complex—[Dy(Cpttt)2][B(C6F5)4], with Cpttt = {C5H2tBu3-1,2,4} and tBu = C(CH3)3—which exhibits magnetic hysteresis at temperatures of up to 60 kelvin at a sweep rate of 22 oersted per second. We observe a clear change in the relaxation dynamics at this temperature, which persists in magnetically diluted samples, suggesting that the origin of the hysteresis is the localized metal-ligand vibrational modes that are unique to dysprosocenium. Ab initio calculations of spin dynamics demonstrate that magnetic relaxation at high temperatures is due to local molecular vibrations. These results indicate that, with judicious molecular design, magnetic data storage in single molecules at temperatures above liquid nitrogen should be possible.

  19. Hysteresis in Magnetocaloric Materials

    DEFF Research Database (Denmark)

    von Moos, Lars

    In this thesis the effects of hysteresis on magnetocaloric material properties and their performance in magnetic refrigeration devices are investigated. This is done through an experimental and model study of first order magnetocaloric materials MnFe(P,As) and Gd5Si2Ge2. The experimental characte......In this thesis the effects of hysteresis on magnetocaloric material properties and their performance in magnetic refrigeration devices are investigated. This is done through an experimental and model study of first order magnetocaloric materials MnFe(P,As) and Gd5Si2Ge2. The experimental...... cases. The Gd5Si2Ge2 model is based on detailed first order reversal curve data, taking both reversible and irreversible properties into account, and is able to reproduce a series of independent experimental results. The Preisach models are applied to simulate material behavior under realistic...... set points, which is demonstrated to induce partial hysteresis loop behavior that will generally underestimate thermal hysteresis. Furthermore it is shown that care should be taken in non-isofield type experiments, as is the case for direct MCE experiments. Measuring the temperature dependence...

  20. Comparison of angular dependence of magnetic Barkhausen noise of hysteresis and initial magnetization curve in API5L steel

    Science.gov (United States)

    Chávez-Gonzalez, A. F.; Martínez-Ortiz, P.; Pérez-Benítez, J. A.; Espina-Hernández, J. H.; Caleyo, F.

    2018-01-01

    This work analyzes the differences between the magnetic Barkhausen noise corresponding to the initial magnetization curve and Barkhausen noise corresponding to one branch of the hysteresis loop in API-5L steel. The outcomes show that the Barkhausen noise signal corresponding to the initial magnetization curve and that corresponding to the hysteresis are significantly different. This difference is due to the presence of different processes of the domain wall dynamics in both phenomena. To study the processes present in magnetization dynamics for an applied field of H > 0, research into the angular dependence of a Barkhausen signal using applied field bands has revealed that a Barkhausen signal corresponding to the initial magnetization curve is more suitable than a Barkhausen signal corresponding to the hysteresis loop.

  1. Analytic synthesis of a hysteresis motor

    International Nuclear Information System (INIS)

    Anih, Linus U.; Obe, Emeka S.; Agbachi, Eugene O.

    2011-01-01

    This paper presents the unique synthesis of a motor with a hysteresis torque-speed characteristic. The machine is synthesized from a conventional polyphase squirrel cage induction motor (SCIM) with a high rotor resistance to leakage reactance r 2 /x 2 ratio, which is mechanically coupled to a polyphase transfer field (TF) machine but with an inversion of the usual torque-speed characteristic of the latter about the speed axis and both machines are connected in parallel to the supply. It is shown that the resultant torque of the combined machines is constant, from standstill to full speed ω 0 , typical of that of a hysteresis motor. Unlike the conventional hysteresis motor, the output torque of the synthesized version can be made large.

  2. Mechanical hysteresis in actin networks.

    Science.gov (United States)

    Majumdar, Sayantan; Foucard, Louis C; Levine, Alex J; Gardel, Margaret L

    2018-03-14

    Understanding the response of complex materials to external force is central to fields ranging from materials science to biology. Here, we describe a novel type of mechanical adaptation in cross-linked networks of F-actin, a ubiquitous protein found in eukaryotic cells. We show that shear stress changes the network's nonlinear mechanical response even long after that stress is removed. The duration, magnitude and direction of forcing history all change this mechanical response. While the mechanical hysteresis is long-lived, it can be simply erased by force application in the opposite direction. We further show that the observed mechanical adaptation is consistent with stress-dependent changes in the nematic order of the constituent filaments. Thus, this mechanical hysteresis arises from the changes in non-linear response that originates from stress-induced changes to filament orientation. This demonstrates that F-actin networks can exhibit analog read-write mechanical hysteretic properties, which can be used for adaptation to mechanical stimuli.

  3. Hysteresis, nucleation and growth phenomena in spin-crossover solids

    Science.gov (United States)

    Ridier, Karl; Molnár, Gábor; Salmon, Lionel; Nicolazzi, William; Bousseksou, Azzedine

    2017-12-01

    The observation and the study of first-order phase transitions in cooperative spin-crossover (SCO) solids exhibiting hysteresis behaviours are of particular interest and currently constitute a burgeoning area in the field of bistable molecular materials. The understanding and the control of the transition mechanisms (nucleation and growth processes) and their dynamics within the hysteresis region appear to be a general and appealing problem from a fundamental point of view and for technological applications as well. This review reports on the recent progresses and most important findings made on the spatiotemporal dynamics of the spin transition in SCO solids, particularly through the universal nucleation and growth process. Both thermally induced and light-induced spin transitions are discussed. We open up this review to the central question of the evolution of the transition mechanisms and dynamics in SCO nano-objects, which constitute promising systems to reach ultra-fast switching, and the experimental issues inherent to such studies at the micro- and nanometric scale.

  4. Hysteresis losses and specific absorption rate measurements in magnetic nanoparticles for hyperthermia applications.

    Science.gov (United States)

    Coïsson, Marco; Barrera, Gabriele; Celegato, Federica; Martino, Luca; Kane, Shashank N; Raghuvanshi, Saroj; Vinai, Franco; Tiberto, Paola

    2017-06-01

    Magnetic hysteresis loops areas and hyperthermia on magnetic nanoparticles have been studied with the aim of providing reliable and reproducible methods of measuring the specific absorption rate (SAR). The SAR of Fe 3 O 4 nanoparticles with two different mean sizes, and Ni 1-x Zn x Fe 2 O 4 ferrites with 0 ≤ x ≤ 0.8 has been measured with three approaches: static hysteresis loops areas, dynamic hysteresis loops areas and hyperthermia of a water solution. For dynamic loops and thermometric measurements, specific experimental setups have been developed, that operate at comparable frequencies (≈ 69kHz and ≈ 100kHz respectively) and rf magnetic field peak values (up to 100mT). The hyperthermia setup has been fully modelled to provide a direct measurement of the SAR of the magnetic nanoparticles by taking into account the heat exchange with the surrounding environment in non-adiabatic conditions and the parasitic heating of the water due to ionic currents. Dynamic hysteresis loops are shown to provide an accurate determination of the SAR except for superparamagnetic samples, where the boundary with a blocked regime could be crossed in dynamic conditions. Static hysteresis loops consistently underestimate the specific absorption rate but can be used to select the most promising samples. A means of reliably measure SAR of magnetic nanoparticles by different approaches for hyperthermia applications is presented and its validity discussed by comparing different methods. This work fits within the general subject of metrological traceability in medicine with a specific focus on magnetic hyperthermia. This article is part of a Special Issue entitled "Recent Advances in Bionanomaterials" Guest Editor: Dr. Marie-Louise Saboungi and Dr. Samuel D. Bader. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Modeling of Hysteresis in Piezoelectric Actuator Based on Segment Similarity

    Directory of Open Access Journals (Sweden)

    Rui Xiong

    2015-11-01

    Full Text Available To successfully exploit the full potential of piezoelectric actuators in micro/nano positioning systems, it is essential to model their hysteresis behavior accurately. A novel hysteresis model for piezoelectric actuator is proposed in this paper. Firstly, segment-similarity, which describes the similarity relationship between hysteresis curve segments with different turning points, is proposed. Time-scale similarity, which describes the similarity relationship between hysteresis curves with different rates, is used to solve the problem of dynamic effect. The proposed model is formulated using these similarities. Finally, the experiments are performed with respect to a micro/nano-meter movement platform system. The effectiveness of the proposed model is verified as compared with the Preisach model. The experimental results show that the proposed model is able to precisely predict the hysteresis trajectories of piezoelectric actuators and performs better than the Preisach model.

  6. Chameleon field dynamics during inflation

    Science.gov (United States)

    Saba, Nasim; Farhoudi, Mehrdad

    By studying the chameleon model during inflation, we investigate whether it can be a successful inflationary model, wherein we employ the common typical potential usually used in the literature. Thus, in the context of the slow-roll approximations, we obtain the e-folding number for the model to verify the ability of resolving the problems of standard big bang cosmology. Meanwhile, we apply the constraints on the form of the chosen potential and also on the equation of state parameter coupled to the scalar field. However, the results of the present analysis show that there is not much chance of having the chameleonic inflation. Hence, we suggest that if through some mechanism the chameleon model can be reduced to the standard inflationary model, then it may cover the whole era of the universe from the inflation up to the late time.

  7. Hysteresis and parent-metabolite analyses unravel characteristic pesticide transport mechanisms in a mixed land use catchment.

    Science.gov (United States)

    Tang, Ting; Stamm, Christian; van Griensven, Ann; Seuntjens, Piet; Bronders, Jan

    2017-11-01

    To properly estimate and manage pesticide occurrence in urban rivers, it is essential, but often highly challenging, to identify the key pesticide transport pathways in association to the main sources. This study examined the concentration-discharge hysteresis behaviour (hysteresis analysis) for three pesticides and the parent-metabolite concentration dynamics for two metabolites at sites with different levels of urban influence in a mixed land use catchment (25 km 2 ) within the Swiss Greifensee area, aiming to identify the dominant pesticide transport pathways. Combining an adapted hysteresis classification framework with prior knowledge of the field conditions and pesticide usage, we demonstrated the possibility of using hysteresis analysis to qualitatively infer the dominant pesticide transport pathway in mixed land-use catchments. The analysis showed that hysteresis types, and therefore the dominant transport pathway, vary among pesticides, sites and rainfall events. Hysteresis loops mostly correspond to dominant transport by flow components with intermediate response time, although pesticide sources indicate that fast transport pathways are responsible in most cases (e.g. urban runoff and combined sewer overflows). The discrepancy suggests the fast transport pathways can be slowed down due to catchment storages, such as topographic depressions in agricultural areas, a wastewater treatment plant (WWTP) and other artificial storage units (e.g. retention basins) in urban areas. Moreover, the WWTP was identified as an important factor modifying the parent-metabolite concentration dynamics during rainfall events. To properly predict and manage pesticide occurrence in catchments of mixed land uses, the hydrological delaying effect and chemical processes within the artificial structures need to be accounted for, in addition to the catchment hydrology and the diversity of pesticide sources. This study demonstrates that in catchments with diverse pesticide sources

  8. Wetting hysteresis of nanodrops on nanorough surfaces

    Science.gov (United States)

    Chang, Cheng-Chung; Sheng, Yu-Jane; Tsao, Heng-Kwong

    2016-10-01

    Nanodrops on smooth or patterned rough surfaces are explored by many-body dissipative particle dynamics to demonstrate the influence of surface roughness on droplet wetting. On a smooth surface, nanodrops exhibit the random motion and contact angle hysteresis is absent. The diffusivity decays as the intrinsic contact angle (θY) decreases. On a rough surface, the contact line is pinned and the most stable contact angle (θY') is acquired. The extent of contact angle hysteresis (Δ θ ) is determined by two approaches, which resemble the inflation-deflation method and inclined plane method for experiments. The hysteresis loop is acquired and both approaches yield consistent results. The influences of wettability and surface roughness on θY' and Δ θ are examined. θY' deviates from that estimated by the Wenzel or Cassie-Baxter models. This consequence can be explained by the extent of impregnation, which varies with the groove position and wettability. Moreover, contact angle hysteresis depends more on the groove width than the depth.

  9. Dynamic shielding of the magnetic fields

    Directory of Open Access Journals (Sweden)

    RAU, M.

    2010-11-01

    Full Text Available The paper presents a comparative study of the methods used to control and compensate the direct and alternative magnetic fields. Two frequently used methods in the electromagnetic compatibility of the complex biomagnetism installations were analyzed. The two methods refer to the use of inductive magnetic field sensors (only for alternative fields and of fluxgate magnetometers as active transducers which measures both the direct and alternative components of the magnetic field. The applications of the dynamic control of the magnetic field are: control of the magnetic field of the military ships, control of parasite magnetic field produced by power transformers and the electrical networks, protection of the mass spectrometers, electronic microscopes, SQUID and optical pumping magnetometers for applications in biomagnetism.

  10. Thermo field dynamics: a quantum field theory at finite temperature

    International Nuclear Information System (INIS)

    Mancini, F.; Marinaro, M.; Matsumoto, H.

    1988-01-01

    A brief review of the theory of thermo field dynamics (TFD) is presented. TFD is introduced and developed by Umezawa and his coworkers at finite temperature. The most significant concept in TFD is that of a thermal vacuum which satisfies some conditions denoted as thermal state conditions. The TFD permits to reformulate theories at finite temperature. There is no need in an additional principle to determine particle distributions at T ≠ 0. Temperature and other macroscopic parameters are introduced in the definition of the vacuum state. All operator formalisms used in quantum field theory at T=0 are preserved, although the field degrees of freedom are doubled. 8 refs

  11. Mean field methods for cortical network dynamics

    DEFF Research Database (Denmark)

    Hertz, J.; Lerchner, Alexander; Ahmadi, M.

    2004-01-01

    We review the use of mean field theory for describing the dynamics of dense, randomly connected cortical circuits. For a simple network of excitatory and inhibitory leaky integrate- and-fire neurons, we can show how the firing irregularity, as measured by the Fano factor, increases with the stren......We review the use of mean field theory for describing the dynamics of dense, randomly connected cortical circuits. For a simple network of excitatory and inhibitory leaky integrate- and-fire neurons, we can show how the firing irregularity, as measured by the Fano factor, increases...

  12. Field based model for pedestrian dynamics

    Science.gov (United States)

    Yu, Bin; Zhang, Michael; Wang, Zhongren

    2018-03-01

    A pedestrian’s physical movement is simulated as a response to the pedestrian subjective evaluation of the objective environment. The objective environment is modeled by presumed fields statically or dynamically superposed. Regulation functions, which consider not only force caused by presumed fields but also local crowd densities around pedestrians, are introduced for consideration of pedestrians’ intelligence. Numerical experiments indicate that the model can be calibrated to reproduce a fundamental diagram that matches an empirical one proposed by Weidmann. Such experiments prove the model to be a useful tool for study of pedestrian dynamics.

  13. Hysteresis in multiphase microfluidics at a T-junction.

    Science.gov (United States)

    Zagnoni, Michele; Anderson, Jamie; Cooper, Jonathan M

    2010-06-15

    Multiphase microfluidics offer a wide range of functionalities in the fields of fluid dynamics, biology, particle synthesis, and, more recently, also in logical computation. In this article, we describe the hysteresis of immiscible, multiphase flow obtained in hydrophilic, microfluidic systems at a T-junction. Stable and unstable state behaviors, in the form of segmented and parallel flow patterns of oil and water, were reliably produced, depending upon the history of the flow rates applied to the phases. The transition mechanisms between the two states were analyzed both experimentally and using numerical simulations, describing how the physical and fluid dynamic parameters influenced the hysteretic behavior of the flow. The characteristics of these multiphase systems render them suitable to be used as pressure comparators and also for the implementation of microfluidic logic operations.

  14. Thermal hysteresis proteins.

    Science.gov (United States)

    Barrett, J

    2001-02-01

    Extreme environments present a wealth of biochemical adaptations. Thermal hysteresis proteins (THPs) have been found in vertebrates, invertebrates, plants, bacteria and fungi and are able to depress the freezing point of water (in the presence of ice crystals) in a non-colligative manner by binding to the surface of nascent ice crystals. The THPs comprise a disparate group of proteins with a variety of tertiary structures and often no common sequence similarities or structural motifs. Different THPs bind to different faces of the ice crystal, and no single mechanism has been proposed to account for THP ice binding affinity and specificity. Experimentally THPs have been used in the cryopreservation of tissues and cells and to induce cold tolerance in freeze susceptible organisms. THPs represent a remarkable example of parallel and convergent evolution with different proteins being adapted for an anti-freeze role.

  15. Local hysteresis in relaxation oscillators

    International Nuclear Information System (INIS)

    Alstroem, P.; Christiansen, B.; Levinsen, M.T.

    1988-01-01

    Relaxation oscillations or 'integrate and fire' phenomena are very commonly found in nature. When modulated by an external force a global hysteresis connected with chaos is often encountered. Besides this kind of hysteresis a local form is found in some systems. We describe briefly the difference and the circumstances under which to observe local hysteresis. A specific system treated in detail is the Fohlmeister model, originally derived to describe a neuronal encoder. In the limit of small damping an analytical solution is obtained. Furthermore, we derive an upper limit to the hysteresis. The results are compared to numerical calculations on the full system and agree quite well. In contrast to e.g. the driven damped pendulum equation the hysteresis is limited in size as compared to the phase-locked region. (orig.)

  16. String Analysis for Dynamic Field Access

    DEFF Research Database (Denmark)

    Madsen, Magnus; Andreasen, Esben

    2014-01-01

    domains to reason about dynamic field access in a static analysis tool. A key feature of the domains is that the equal, concatenate and join operations take Ο(1) time. Experimental evaluation on four common JavaScript libraries, including jQuery and Prototype, shows that traditional string domains...

  17. Dynamical interplay between fluctuations, electric fields and ...

    Indian Academy of Sciences (India)

    similarity in the scaling properties of the probability distribution function (PDF) of turbulent transport has been observed in the plasma edge region in fusion plasmas. The investigation of the dynamical interplay between fluctuation in gradients, turbulent transport and radial electric fields has shown that these parameters are ...

  18. Controlling Josephson dynamics by strong microwave fields

    NARCIS (Netherlands)

    Chesca, B.; Savel'ev, E.; Rakhmanov, A.L.; Smilde, H.J.H.; Hilgenkamp, Johannes W.M.

    2008-01-01

    We observe several sharp changes in the slope of the current-voltage characteristics (CVCs) of thin-film ramp-edge Josephson junctions between YBa2Cu3O7−delta and Nb when applying strong microwave fields. Such behavior indicates an intriguing Josephson dynamics associated with the switching from a

  19. Field dynamics inference via spectral density estimation

    Science.gov (United States)

    Frank, Philipp; Steininger, Theo; Enßlin, Torsten A.

    2017-11-01

    Stochastic differential equations are of utmost importance in various scientific and industrial areas. They are the natural description of dynamical processes whose precise equations of motion are either not known or too expensive to solve, e.g., when modeling Brownian motion. In some cases, the equations governing the dynamics of a physical system on macroscopic scales occur to be unknown since they typically cannot be deduced from general principles. In this work, we describe how the underlying laws of a stochastic process can be approximated by the spectral density of the corresponding process. Furthermore, we show how the density can be inferred from possibly very noisy and incomplete measurements of the dynamical field. Generally, inverse problems like these can be tackled with the help of Information Field Theory. For now, we restrict to linear and autonomous processes. To demonstrate its applicability, we employ our reconstruction algorithm on a time-series and spatiotemporal processes.

  20. On the use of magnetic hysteresis in paleomagnetism for granulometry

    Science.gov (United States)

    Tauxe, L.; Yu, Y.

    2004-05-01

    In environmental magnetism and paleomagnetism, measuring magnetic hysteresis has become a routine routine procedure for characterizing remanence carriers of rocks. In general, values of saturation magnetization (Ms), saturation remanence (Mr), and coercivity (Bc) are determined from hysteresis loops after appropriate non-ferrimagnetic slope correction. In addition, values of remanence coercivity (Bcr) are generally obtained from separate backfield measurements. The conventional hysteresis measurements have recently been extended to include the very time consuming first order reversal curves (FORCs). In this presentation, we discuss two approaches for determining average grain size accurately and rapidly from hysteresis measurements. (1) Squareness-Coercivity (SC) analysis: Plots of squareness (Mr/Ms) versus Bc characterize not only grain size but also dominant anisotropy, temperature dependence, and volume concentration with better resolution than the traditional Day plot squareness versus (Mr/Ms versus Bcr/Bc). SC plots are being calibrated using micromagnetic simultions which agree very well with experimental results. (2) Transient Hysteresis (TH) Transient hysteresis is determined from a partial hysteresis curve in which samples are exposed to a saturation field which is reduced to zero, then increased again to saturation in the same direction. This is a single FORC with the minimum field being zero. The area between the ascending and descending loop is the "transient hysteresis" TH. Micromagnetic modeling and experiments shows TH to be an excellent granulometric indicator. In particular, it clearly distinguishes superparamagnetic (SP) grain from multidomain (MD) since TH results from the action of self-demagnetization that is absent for SP. While many factors such as composition (lithology), field-treatment, grain shape and size, pre-history, stress, and volume concentration affect hysteresis properties, a combination of SC and TH predict with some confidence

  1. Dynamic Neural Fields with Intrinsic Plasticity.

    Science.gov (United States)

    Strub, Claudius; Schöner, Gregor; Wörgötter, Florentin; Sandamirskaya, Yulia

    2017-01-01

    Dynamic neural fields (DNFs) are dynamical systems models that approximate the activity of large, homogeneous, and recurrently connected neural networks based on a mean field approach. Within dynamic field theory, the DNFs have been used as building blocks in architectures to model sensorimotor embedding of cognitive processes. Typically, the parameters of a DNF in an architecture are manually tuned in order to achieve a specific dynamic behavior (e.g., decision making, selection, or working memory) for a given input pattern. This manual parameters search requires expert knowledge and time to find and verify a suited set of parameters. The DNF parametrization may be particular challenging if the input distribution is not known in advance, e.g., when processing sensory information. In this paper, we propose the autonomous adaptation of the DNF resting level and gain by a learning mechanism of intrinsic plasticity (IP). To enable this adaptation, an input and output measure for the DNF are introduced, together with a hyper parameter to define the desired output distribution. The online adaptation by IP gives the possibility to pre-define the DNF output statistics without knowledge of the input distribution and thus, also to compensate for changes in it. The capabilities and limitations of this approach are evaluated in a number of experiments.

  2. Confinement dynamics in the reversed field pinch

    International Nuclear Information System (INIS)

    Schoenberg, K.F.

    1988-01-01

    The study of basic transport and confinement dynamics is central to the development of the reversed field pinch (RFP) as a confinement concept. Thus, the goal of RFP research is to understand the connection between processes that sustain the RFP configuration and related transport/confinement properties. Recently, new insights into confinement have emerged from a detailed investigation of RFP electron and ion physics. These insights derive from the recognition that both magnetohydrodynamic (MHD) and electron kinetic effects play an important and strongly coupled role in RFP sustainment and confinement dynamics. In this paper, we summarize the results of these studies on the ZT-40M experiment. 8 refs

  3. Dynamic Magnetic Field Applications for Materials Processing

    Science.gov (United States)

    Mazuruk, K.; Grugel, Richard N.; Motakef, S.; Whitaker, Ann F. (Technical Monitor)

    2001-01-01

    Magnetic fields, variable in time and space, can be used to control convection in electrically conducting melts. Flow induced by these fields has been found to be beneficial for crystal growth applications. It allows increased crystal growth rates, and improves homogeneity and quality. Particularly beneficial is the natural convection damping capability of alternating magnetic fields. One well-known example is the rotating magnetic field (RMF) configuration. RMF induces liquid motion consisting of a swirling basic flow and a meridional secondary flow. In addition to crystal growth applications, RMF can also be used for mixing non-homogeneous melts in continuous metal castings. These applied aspects have stimulated increasing research on RMF-induced fluid dynamics. A novel type of magnetic field configuration consisting of an axisymmetric magnetostatic wave, designated the traveling magnetic field (TMF), has been recently proposed. It induces a basic flow in the form of a single vortex. TMF may find use in crystal growth techniques such as the vertical Bridgman (VB), float zone (FZ), and the traveling heater method. In this review, both methods, RMF and TMF are presented. Our recent theoretical and experimental results include such topics as localized TMF, natural convection dumping using TMF in a vertical Bridgman configuration, the traveling heater method, and the Lorentz force induced by TMF as a function of frequency. Experimentally, alloy mixing results, with and without applied TMF, will be presented. Finally, advantages of the traveling magnetic field, in comparison to the more mature rotating magnetic field method, will be discussed.

  4. Ultracold plasma dynamics in a magnetic field

    Science.gov (United States)

    Zhang, Xianli

    Plasmas, often called the fourth state of matter and the most common one in the universe, have parameters varying by many orders of magnitude, from temperature of a few hundred kelvin in the Earth's ionosphere to 10 16 K in the magnetosphere of a pulsar. Ultracold plasmas, produced by photoionizing a sample of laser-cooled and trapped atoms near the ionization limit, have extended traditional neutral plasma parameters by many orders of magnitude, to electron temperatures below 1 K and ion temperatures in the tens of muK to a few Kelvin, and densities of 105 cm -3 to 1010 cm-3. These plasmas thus provide a testing ground to study basic plasma theory in a clean and simple system with or without a magnetic field. Previous studies of ultracold plasmas have primarily concentrated on temperature measurements, collective modes and expansion dynamics in the absence of magnetic fields. This thesis presents the first study of ultracold plasma dynamics in a magnetic field. The presence of a magnetic field during the expansion can initiate various phenomena, such as plasma confinement and plasma instabilities. While the electron temperatures are very low in ultracold plasmas, we need only tens of Gauss of magnetic field to observe significant effects on the expansion dynamics. To probe the ultraocold plasma dynamics in a magnetic field, we developed a new diagnostic - projection imaging, which images the ion distribution by extracting the ions with a high voltage pulse onto a position-sensitive detector. Early in the lifetime of the plasma (explosion of the dense ion cloud. For later times, we measure the 2-D Gaussian width of the ion image, obtaining the transverse expansion velocity as a function of magnetic field (up to 70 G), and observe that the transverse expansion velocity scales as B-1/2, explained by a nonlinear ambipolar diffusion model that involes anisotropic diffusion in two different directions. We also present the first observation of a plasma instability in an

  5. Dynamics of coupled phantom and tachyon fields

    Energy Technology Data Exchange (ETDEWEB)

    Shahalam, M. [Zhejiang University of Technology, Institute for Advanced Physics and Mathematics, Hangzhou (China); Pathak, S.D.; Li, Shiyuan [Shandong University, School of Physics, Jinan (China); Myrzakulov, R. [Eurasian National University, Department of General and Theoretical Physics, Eurasian International Center for Theoretical Physics, Astana (Kazakhstan); Wang, Anzhong [Zhejiang University of Technology, Institute for Advanced Physics and Mathematics, Hangzhou (China); Baylor University, Department of Physics, GCAP-CASPER, Waco, TX (United States)

    2017-10-15

    In this paper, we apply the dynamical analysis to a coupled phantom field with scaling potential taking particular forms of the coupling (linear and combination of linear), and present phase space analysis. We investigate if there exists a late time accelerated scaling attractor that has the ratio of dark energy and dark matter densities of the order one. We observe that the scrutinized couplings cannot alleviate the coincidence problem, however, they acquire stable late time accelerated solutions. We also discuss a coupled tachyon field with inverse square potential assuming linear coupling. (orig.)

  6. Modeling emotional dynamics : currency versus field.

    Energy Technology Data Exchange (ETDEWEB)

    Sallach, D .L.; Decision and Information Sciences; Univ. of Chicago

    2008-08-01

    Randall Collins has introduced a simplified model of emotional dynamics in which emotional energy, heightened and focused by interaction rituals, serves as a common denominator for social exchange: a generic form of currency, except that it is active in a far broader range of social transactions. While the scope of this theory is attractive, the specifics of the model remain unconvincing. After a critical assessment of the currency theory of emotion, a field model of emotion is introduced that adds expressiveness by locating emotional valence within its cognitive context, thereby creating an integrated orientation field. The result is a model which claims less in the way of motivational specificity, but is more satisfactory in modeling the dynamic interaction between cognitive and emotional orientations at both individual and social levels.

  7. Dynamical symmetry breaking in quantum field theories

    CERN Document Server

    Miransky, Vladimir A

    1993-01-01

    The phenomenon of dynamical symmetry breaking (DSB) in quantum field theory is discussed in a detailed and comprehensive way. The deep connection between this phenomenon in condensed matter physics and particle physics is emphasized. The realizations of DSB in such realistic theories as quantum chromodynamics and electroweak theory are considered. Issues intimately connected with DSB such as critical phenomenona and effective lagrangian approach are also discussed.

  8. Molecular dynamics in high electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Apostol, M., E-mail: apoma@theory.nipne.ro; Cune, L.C.

    2016-06-15

    Highlights: • New method for rotation molecular spectra in high electric fields. • Parametric resonances – new features in spectra. • New elementary excitations in polar solids from dipolar interaction (“dipolons”). • Discussion about a possible origin of the ferroelectricity from dipolar interactions. - Abstract: Molecular rotation spectra, generated by the coupling of the molecular electric-dipole moments to an external time-dependent electric field, are discussed in a few particular conditions which can be of some experimental interest. First, the spherical-pendulum molecular model is reviewed, with the aim of introducing an approximate method which consists in the separation of the azimuthal and zenithal motions. Second, rotation spectra are considered in the presence of a static electric field. Two particular cases are analyzed, corresponding to strong and weak fields. In both cases the classical motion of the dipoles consists of rotations and vibrations about equilibrium positions; this motion may exhibit parametric resonances. For strong fields a large macroscopic electric polarization may appear. This situation may be relevant for polar matter (like pyroelectrics, ferroelectrics), or for heavy impurities embedded in a polar solid. The dipolar interaction is analyzed in polar condensed matter, where it is shown that new polarization modes appear for a spontaneous macroscopic electric polarization (these modes are tentatively called “dipolons”); one of the polarization modes is related to parametric resonances. The extension of these considerations to magnetic dipoles is briefly discussed. The treatment is extended to strong electric fields which oscillate with a high frequency, as those provided by high-power lasers. It is shown that the effect of such fields on molecular dynamics is governed by a much weaker, effective, renormalized, static electric field.

  9. Molecular dynamics in high electric fields

    International Nuclear Information System (INIS)

    Apostol, M.; Cune, L.C.

    2016-01-01

    Highlights: • New method for rotation molecular spectra in high electric fields. • Parametric resonances – new features in spectra. • New elementary excitations in polar solids from dipolar interaction (“dipolons”). • Discussion about a possible origin of the ferroelectricity from dipolar interactions. - Abstract: Molecular rotation spectra, generated by the coupling of the molecular electric-dipole moments to an external time-dependent electric field, are discussed in a few particular conditions which can be of some experimental interest. First, the spherical-pendulum molecular model is reviewed, with the aim of introducing an approximate method which consists in the separation of the azimuthal and zenithal motions. Second, rotation spectra are considered in the presence of a static electric field. Two particular cases are analyzed, corresponding to strong and weak fields. In both cases the classical motion of the dipoles consists of rotations and vibrations about equilibrium positions; this motion may exhibit parametric resonances. For strong fields a large macroscopic electric polarization may appear. This situation may be relevant for polar matter (like pyroelectrics, ferroelectrics), or for heavy impurities embedded in a polar solid. The dipolar interaction is analyzed in polar condensed matter, where it is shown that new polarization modes appear for a spontaneous macroscopic electric polarization (these modes are tentatively called “dipolons”); one of the polarization modes is related to parametric resonances. The extension of these considerations to magnetic dipoles is briefly discussed. The treatment is extended to strong electric fields which oscillate with a high frequency, as those provided by high-power lasers. It is shown that the effect of such fields on molecular dynamics is governed by a much weaker, effective, renormalized, static electric field.

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

    KAUST Repository

    Xu, Jixian

    2015-05-08

    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. Hysteresis in simulations of malaria transmission

    Science.gov (United States)

    Yamana, Teresa K.; Qiu, Xin; Eltahir, Elfatih A. B.

    2017-10-01

    Malaria transmission is a complex system and in many parts of the world is closely related to climate conditions. However, studies on environmental determinants of malaria generally consider only concurrent climate conditions and ignore the historical or initial conditions of the system. Here, we demonstrate the concept of hysteresis in malaria transmission, defined as non-uniqueness of the relationship between malaria prevalence and concurrent climate conditions. We show the dependence of simulated malaria transmission on initial prevalence and the initial level of human immunity in the population. Using realistic time series of environmental variables, we quantify the effect of hysteresis in a modeled population. In a set of numerical experiments using HYDREMATS, a field-tested mechanistic model of malaria transmission, the simulated maximum malaria prevalence depends on both the initial prevalence and the initial level of human immunity in the population. We found the effects of initial conditions to be of comparable magnitude to the effects of interannual variability in environmental conditions in determining malaria prevalence. The memory associated with this hysteresis effect is longer in high transmission settings than in low transmission settings. Our results show that efforts to simulate and forecast malaria transmission must consider the exposure history of a location as well as the concurrent environmental drivers.

  12. Dynamical Field Model of Hand Preference

    Science.gov (United States)

    Franceschetti, Donald R.; Cantalupo, Claudio

    2000-11-01

    Dynamical field models of information processing in the nervous system are being developed by a number of groups of psychologists and physicists working together to explain The details of behaviors exhibited by a number of animal species. Here we adapt such a model to the expression of hand preference in a small primate, the bushbaby (Otolemur garnetti) . The model provides a theoretical foundation for the interpretation of an experiment currently underway in which a several of these animals are forced to extend either right or left hand to retrieve a food item from a rotating turntable.

  13. Point defects dynamics in a stress field

    International Nuclear Information System (INIS)

    Smetniansky de De Grande, Nelida.

    1989-01-01

    The dependence of anisotropic defect diffusion on stress is studied for a hexagonal close packed (hcp) material under irradiation and uniaxially stressed. The diffusion is described as a discrete process of thermally activated jumps. It is shown that the presence of an external stress field enhances the intrinsic anisotropic diffusion, being this variation determined by the defect dipole tensors' symmetry in the equilibrium and saddle point configurations. Also, the point defect diffusion equations to sinks, like edge dislocations and spherical cavities, are solved and the sink strengths are calculated. The conclusion is that the dynamics of the interaction between defects and sinks is controlled by the changes in diffusivity induced by stress fields. (Author) [es

  14. Hysteresis and strain hardening in the creep response of a polyaniline ER fluid.

    Science.gov (United States)

    Hiamtup, Piyanoot; Sirivat, Anuvat; Jamieson, Alexander M

    2008-09-01

    The electrorheological creep response of PANI/silicone oil suspensions near the yield point is investigated using parallel plate rheometry. Controlled-stress, thixotropic loop experiments exhibit a pronounced hysteresis, from which we determined the static yield stress (sigma(y(static))), as the stress where onset of flow occurs on the upward part of the loop, and a dynamic yield stress (sigma(y(dynamic))), defined as the stress at which flow ceases on the downward part of the loop. The magnitude of the hysteresis, as characterized by the area under the loop, increases substantially with applied field strength and particle concentration, but decreases with increase of temperature. Consistent with literature data, the creep compliance shows an evolution from viscoelastic to viscoplastic to viscous flow behavior as the applied stress increases through the yield point. In the viscoplastic regime, the apparent equilibrium compliance, J(e)(app), shows a discrete pre-yield transition to higher values, indicating a seemingly-enhanced ductility as the applied stress nears the yield point. Measurement of the static yield stress following these creep experiments suggests that the origin of this transition is a pronounced strain-hardening effect. We conclude that strain-hardening contributes to the hysteresis observed in the thixotropic loop test.

  15. Dynamic pulsed-field-gradient NMR

    CERN Document Server

    Sørland, Geir Humborstad

    2014-01-01

    Dealing with the basics, theory and applications of dynamic pulsed-field-gradient NMR NMR (PFG NMR), this book describes the essential theory behind diffusion in heterogeneous media that can be combined with NMR measurements to extract important information of the system being investigated. This information could be the surface to volume ratio, droplet size distribution in emulsions, brine profiles, fat content in food stuff, permeability/connectivity in porous materials and medical applications currently being developed. Besides theory and applications it will provide the readers with background knowledge on the experimental set-ups, and most important, deal with the pitfalls that are numerously present in work with PFG-NMR. How to analyze the NMR data and some important basic knowledge on the hardware will be explained, too.

  16. Nonlinear dynamics in the relativistic field equation

    International Nuclear Information System (INIS)

    Tanaka, Yosuke; Mizuno, Yuji; Kado, Tatsuhiko; Zhao, Hua-An

    2007-01-01

    We have investigated relativistic equations and chaotic behaviors of the gravitational field with the use of general relativity and nonlinear dynamics. The space component of the Friedmann equation shows chaotic behaviors in case of the inflation (h=G-bar /G>0) and open (ζ=-1) universe. In other cases (h= 0 andx-bar 0 ) and the parameters (a, b, c and d); (2) the self-similarity of solutions in the x-x-bar plane and the x-ρ plane. We carried out the numerical calculations with the use of the microsoft EXCEL. The self-similarity and the hierarchy structure of the universe have been also discussed on the basis of E-infinity theory

  17. Research on the Hysteresis Effect on Positioning the System with Flexible Elements

    Directory of Open Access Journals (Sweden)

    Audrius Čereška

    2015-03-01

    Full Text Available The paper analyzes the hysteresis phenomenon of positioning systems with flexible elements for transmitting motion of which piezoelectric actuators are used. The article investigates the influence of hysteresis on the accuracy of positioning systems. A special test bench for conducting research and stand-up methodology for carrying out experimental researches have been used. The test bench includes a computer piezo controller, an inductive displacement sensor and a dynamic data collector used for gathering data and transmitting it to the software package. Mathematical modelling of hysteresis using Matlab/Simulink software package has been done. The performed research has shown that the hysteresis model of maximum dispersion error compared to experimental results makes less than 5%. Thus, it can be stated that the selected method for hysteresis modelling is suitable for precision positioning systems having deformable elements and controlled employing piezoelectric actuators to model hysteresis.

  18. Nonequilibrium dynamical mean-field theory

    International Nuclear Information System (INIS)

    Eckstein, Martin

    2009-01-01

    The aim of this thesis is the investigation of strongly interacting quantum many-particle systems in nonequilibrium by means of the dynamical mean-field theory (DMFT). An efficient numerical implementation of the nonequilibrium DMFT equations within the Keldysh formalism is provided, as well a discussion of several approaches to solve effective single-site problem to which lattice models such as the Hubbard-model are mapped within DMFT. DMFT is then used to study the relaxation of the thermodynamic state after a sudden increase of the interaction parameter in two different models: the Hubbard model and the Falicov-Kimball model. In the latter case an exact solution can be given, which shows that the state does not even thermalize after infinite waiting times. For a slow change of the interaction, a transition to adiabatic behavior is found. The Hubbard model, on the other hand, shows a very sensitive dependence of the relaxation on the interaction, which may be called a dynamical phase transition. Rapid thermalization only occurs at the interaction parameter which corresponds to this transition. (orig.)

  19. Nonequilibrium dynamical mean-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Eckstein, Martin

    2009-12-21

    The aim of this thesis is the investigation of strongly interacting quantum many-particle systems in nonequilibrium by means of the dynamical mean-field theory (DMFT). An efficient numerical implementation of the nonequilibrium DMFT equations within the Keldysh formalism is provided, as well a discussion of several approaches to solve effective single-site problem to which lattice models such as the Hubbard-model are mapped within DMFT. DMFT is then used to study the relaxation of the thermodynamic state after a sudden increase of the interaction parameter in two different models: the Hubbard model and the Falicov-Kimball model. In the latter case an exact solution can be given, which shows that the state does not even thermalize after infinite waiting times. For a slow change of the interaction, a transition to adiabatic behavior is found. The Hubbard model, on the other hand, shows a very sensitive dependence of the relaxation on the interaction, which may be called a dynamical phase transition. Rapid thermalization only occurs at the interaction parameter which corresponds to this transition. (orig.)

  20. The Kurzweil integral and hysteresis

    International Nuclear Information System (INIS)

    Krejci, P

    2006-01-01

    A hysteresis operator, called the play, with variable (possibly degenerate) characteristics, is considered in the space of right-continuous regulated functions. The Lipschitz continuity of the input-output mapping is proved by means of a new technique based on the Kurzweil integral

  1. Dynamics of the Random Field Ising Model

    Science.gov (United States)

    Xu, Jian

    The Random Field Ising Model (RFIM) is a general tool to study disordered systems. Crackling noise is generated when disordered systems are driven by external forces, spanning a broad range of sizes. Systems with different microscopic structures such as disordered mag- nets and Earth's crust have been studied under the RFIM. In this thesis, we investigated the domain dynamics and critical behavior in two dipole-coupled Ising ferromagnets Nd2Fe14B and LiHoxY 1-xF4. With Tc well above room temperature, Nd2Fe14B has shown reversible disorder when exposed to an external transverse field and crosses between two universality classes in the strong and weak disorder limits. Besides tunable disorder, LiHoxY1-xF4 has shown quantum tunneling effects arising from quantum fluctuations, providing another mechanism for domain reversal. Universality within and beyond power law dependence on avalanche size and energy were studied in LiHo0.65Y0.35 F4.

  2. Hysteresis force loss and damping properties in a practical magnet-superconductor maglev test vehicle

    Energy Technology Data Exchange (ETDEWEB)

    Yang Wenjiang; Liu Yu; Wen Zheng; Chen Xiaodong; Duan Yi [School of Astronautics, Beijing University of Aeronautics and Astronautics, Beijing 100083 (China)

    2008-01-15

    In order to investigate the feasible application of a permanent magnet-high-temperature superconductor (PM-HTS) interaction maglev system to a maglev train or a space vehicle launcher, we have constructed a demonstration maglev test vehicle. The force dissipation and damping of the maglev vehicle against external disturbances are studied in a wide range of amplitudes and frequencies by using a sine vibration testing set-up. The dynamic levitation force shows a typical hysteresis behavior, and the force loss is regarded as the hysteresis loss, which is believed to be due to flux motions in superconductors. In this study, we find that the hysteresis loss has weak frequency dependence at small amplitudes and that the dependence increases as the amplitude grows. To analyze the damping properties of the maglev vehicle at different field cooling (FC) conditions, we also employ a transient vibration testing technique. The maglev vehicle shows a very weak damping behavior, and the damping is almost unaffected by the trapped flux of the HTSs in different FC conditions, which is believed to be attributed to the strong pinning in melt-textured HTSs.

  3. Hysteresis force loss and damping properties in a practical magnet superconductor maglev test vehicle

    Science.gov (United States)

    Yang, Wenjiang; Liu, Yu; Wen, Zheng; Chen, Xiaodong; Duan, Yi

    2008-01-01

    In order to investigate the feasible application of a permanent magnet-high-temperature superconductor (PM-HTS) interaction maglev system to a maglev train or a space vehicle launcher, we have constructed a demonstration maglev test vehicle. The force dissipation and damping of the maglev vehicle against external disturbances are studied in a wide range of amplitudes and frequencies by using a sine vibration testing set-up. The dynamic levitation force shows a typical hysteresis behavior, and the force loss is regarded as the hysteresis loss, which is believed to be due to flux motions in superconductors. In this study, we find that the hysteresis loss has weak frequency dependence at small amplitudes and that the dependence increases as the amplitude grows. To analyze the damping properties of the maglev vehicle at different field cooling (FC) conditions, we also employ a transient vibration testing technique. The maglev vehicle shows a very weak damping behavior, and the damping is almost unaffected by the trapped flux of the HTSs in different FC conditions, which is believed to be attributed to the strong pinning in melt-textured HTSs.

  4. Classification of networks of automata by dynamical mean field theory

    International Nuclear Information System (INIS)

    Burda, Z.; Jurkiewicz, J.; Flyvbjerg, H.

    1990-01-01

    Dynamical mean field theory is used to classify the 2 24 =65,536 different networks of binary automata on a square lattice with nearest neighbour interactions. Application of mean field theory gives 700 different mean field classes, which fall in seven classes of different asymptotic dynamics characterized by fixed points and two-cycles. (orig.)

  5. A Highly Accurate Approach for Aeroelastic System with Hysteresis Nonlinearity

    Directory of Open Access Journals (Sweden)

    C. C. Cui

    2017-01-01

    Full Text Available We propose an accurate approach, based on the precise integration method, to solve the aeroelastic system of an airfoil with a pitch hysteresis. A major procedure for achieving high precision is to design a predictor-corrector algorithm. This algorithm enables accurate determination of switching points resulting from the hysteresis. Numerical examples show that the results obtained by the presented method are in excellent agreement with exact solutions. In addition, the high accuracy can be maintained as the time step increases in a reasonable range. It is also found that the Runge-Kutta method may sometimes provide quite different and even fallacious results, though the step length is much less than that adopted in the presented method. With such high computational accuracy, the presented method could be applicable in dynamical systems with hysteresis nonlinearities.

  6. A self-adaption compensation control for hysteresis nonlinearity in piezo-actuated stages based on Pi-sigma fuzzy neural network

    Science.gov (United States)

    Xu, Rui; Zhou, Miaolei

    2018-04-01

    Piezo-actuated stages are widely applied in the high-precision positioning field nowadays. However, the inherent hysteresis nonlinearity in piezo-actuated stages greatly deteriorates the positioning accuracy of piezo-actuated stages. This paper first utilizes a nonlinear autoregressive moving average with exogenous inputs (NARMAX) model based on the Pi-sigma fuzzy neural network (PSFNN) to construct an online rate-dependent hysteresis model for describing the hysteresis nonlinearity in piezo-actuated stages. In order to improve the convergence rate of PSFNN and modeling precision, we adopt the gradient descent algorithm featuring three different learning factors to update the model parameters. The convergence of the NARMAX model based on the PSFNN is analyzed effectively. To ensure that the parameters can converge to the true values, the persistent excitation condition is considered. Then, a self-adaption compensation controller is designed for eliminating the hysteresis nonlinearity in piezo-actuated stages. A merit of the proposed controller is that it can directly eliminate the complex hysteresis nonlinearity in piezo-actuated stages without any inverse dynamic models. To demonstrate the effectiveness of the proposed model and control methods, a set of comparative experiments are performed on piezo-actuated stages. Experimental results show that the proposed modeling and control methods have excellent performance.

  7. Dynamic reconstruction algorithm of temperature field based on Kalman filter

    Science.gov (United States)

    Li, Yanqiu; Liu, Shi; Han, Ren

    2017-05-01

    Development of temperature reconstruction algorithm plays an important role in the application of temperature field measurement by acoustic tomography. A dynamic model of temperature field reconstruction by acoustic tomography is established. A dynamic reconstruction algorithm based on Kalman Filter (KF) is proposed considering both acoustic measurement and the dynamic evolution information. An objective function fusing space constrain with dynamic evolution information is designed. Simulation results of three temperature field distribution models show that the reconstruction quality of dynamic reconstruction method based on KF is better than those of static reconstruction methods.

  8. Discriminator with a small hysteresis

    International Nuclear Information System (INIS)

    Korol'ko, E.V.; Suvorov, V.V.

    1977-01-01

    The electric circuitry of a discriminator is described which comprises a current shaping circuit, a tunnel diode and a shunting circuit. The novel shunting circuit design ensures a small hysteresis and quick response of the system as a whole. The shunting circuit employs two n-p-n and p-n-p type transistors, their emitters being interconnected and the bases being coupled to voltage dividers. A diagram is presented to illustrate the function of the tunnel diode - shunting circuit combination. The discriminator has the following characteristics: hysteresis about 5%, response time about 15 nsec., attenuation factor about 3. The discriminator is useful for forming pulses having a duration equal to the threshold exceeding time

  9. Hysteresis in a superfluid atom circuit

    Energy Technology Data Exchange (ETDEWEB)

    Song, Tieling; Zhou, D.L., E-mail: zhoudl72@iphy.ac.cn

    2016-09-15

    We study a hysteresis phenomenon in a rotating BEC with a weak link in a quasi-one-dimensional torus by proposing a microscopic theoretical model including a dissipation bath. By analyzing the role of dissipation and the decay rates of all the energy levels, we are able to give a microscopic interpretation of hysteresis recently observed in the experiment and confirm that the hysteresis is the result of the presence of metastable state. In particular, we obtain the hysteresis loops in a quench process just as that in the experiment. We also find that the shape and size of the hysteresis loop change drastically with the strength of the link.

  10. The Kurzweil integral and hysteresis

    Czech Academy of Sciences Publication Activity Database

    Krejčí, Pavel

    2006-01-01

    Roč. 55, - (2006), s. 144-154 ISSN 1742-6588. [ International Workshop on Multi-Rate Processes and Hysteresis. Cork, 03.04.2006-08.04.2006] Institutional research plan: CEZ:AV0Z10190503 Keywords : regulated functions * space Subject RIV: BA - General Mathematics http://iopscience.iop.org/1742-6596/55/1/014/pdf/1742-6596_55_1_014.pdf

  11. Theoretical approach to the magnetocaloric effect with hysteresis

    International Nuclear Information System (INIS)

    Basso, V.; Bertotti, G.; LoBue, M.; Sasso, C.P.

    2005-01-01

    In this paper a thermodynamic model with internal variables is presented and applied to ferromagnetic hysteresis. The out-of-equilibrium Gibbs free energy of a magnetic system is expressed as a function of the internal state of the Preisach model. Expressions for the system entropy and the entropy production are derived. By this approach it is possible to reproduce the characteristic features of the experimentally observed temperature changes (of the order of 10 -4 K around room temperature) induced by the magnetic field along the hysteresis loop performed in iron under adiabatic condition

  12. Hysteresis losses in a dense superparamagnetic nanoparticle assembly

    Directory of Open Access Journals (Sweden)

    S. A. Gudoshnikov

    2012-03-01

    Full Text Available The hysteresis losses of a dense assembly of magnetite nanoparticles with an average diameter D = 25 nm are measured in the frequency range f = 10 – 200 kHz for magnetic field amplitudes up to H0 = 400 Oe. The low frequency hysteresis loops of the assembly are obtained by means of integration of the electro-motive force signal arising in a small pick-up coil wrapped around a sample which contains 1 – 5 mg of a magnetite powder. It is proved experimentally that the specific absorption rate diminishes approximately 4.5 times when the sample aspect ratio decreases from 11.4 to 1. Theoretical estimate shows that experimentally measured hysteresis loops can be approximately described only by taking into account appreciable contributions of magnetic nanoparticles of both very small, D 30 nm, diameters. Thus the wide particle size distribution has to be assumed.

  13. Singularity and dynamics on discontinuous vector fields

    CERN Document Server

    Luo, Albert CJ

    2006-01-01

    This book discussed fundamental problems in dynamics, which extensively exist in engineering, natural and social sciences. The book presented a basic theory for the interactions among many dynamical systems and for a system whose motions are constrained naturally or artificially. The methodology and techniques presented in this book are applicable to discontinuous dynamical systems in physics, engineering and control. In addition, they may provide useful tools to solve non-traditional dynamics in biology, stock market and internet network et al, which cannot be easily solved by the traditional

  14. Dynamics of polymers: a mean-field theory.

    Science.gov (United States)

    Fredrickson, Glenn H; Orland, Henri

    2014-02-28

    We derive a general mean-field theory of inhomogeneous polymer dynamics; a theory whose form has been speculated and widely applied, but not heretofore derived. Our approach involves a functional integral representation of a Martin-Siggia-Rose (MSR) type description of the exact many-chain dynamics. A saddle point approximation to the generating functional, involving conditions where the MSR action is stationary with respect to a collective density field ρ and a conjugate MSR response field ϕ, produces the desired dynamical mean-field theory. Besides clarifying the proper structure of mean-field theory out of equilibrium, our results have implications for numerical studies of polymer dynamics involving hybrid particle-field simulation techniques such as the single-chain in mean-field method.

  15. Dynamical interplay between fluctuations, electric fields and ...

    Indian Academy of Sciences (India)

    interplay between fluctuation in gradients, turbulent transport and radial electric fields has shown that these parameters ... electric fields and density fluctuations, ΓE¢B(t) = ˜n(t) ˜Eθ (t)/B. The poloidal electric field has been .... transport increases and the system performs a relaxation which tends to drive the plasma back to the ...

  16. Gas dynamics in strong centrifugal fields

    Energy Technology Data Exchange (ETDEWEB)

    Bogovalov, S.V.; Kislov, V.A.; Tronin, I.V. [National research nuclear university “MEPhI”, Kashirskoje shosse, 31,115409, Moscow (Russian Federation)

    2015-03-10

    Dynamics of waves generated by scopes in gas centrifuges (GC) for isotope separation is considered. The centrifugal acceleration in the GC reaches values of the order of 106g. The centrifugal and Coriolis forces modify essentially the conventional sound waves. Three families of the waves with different polarisation and dispersion exist in these conditions. Dynamics of the flow in the model GC Iguasu is investigated numerically. Comparison of the results of the numerical modelling of the wave dynamics with the analytical predictions is performed. New phenomena of the resonances in the GC is found. The resonances occur for the waves polarized along the rotational axis having the smallest dumping due to the viscosity.

  17. Gas dynamics in strong centrifugal fields

    OpenAIRE

    Bogovalov, S. V.; Kislov, V. A.; Tronin, I. V.

    2017-01-01

    Dynamics of waves generated by scopes in gas centrifuges (GC) for isotope separation is considered. The centrifugal acceleration in the GC reaches values of the order of $10^6$g. The centrifugal and Coriolis forces modify essentially the conventional sound waves. Three families of the waves with different polarisation and dispersion exist in these conditions. Dynamics of the flow in the model GC Iguasu is investigated numerically. Comparison of the results of the numerical modelling of the wa...

  18. HTSL massive motor. Project: Motor field calculation. Final report

    International Nuclear Information System (INIS)

    Gutt, H.J.; Gruener, A.

    2003-01-01

    HTS motors up to 300 kW were to be developed and optimized. For this, specific calculation methods were enhanced to include superconducting rotor types (hysteresis, reluctance and permanent magnet HTS rotors). The experiments were carried out in a SHM70-45 hysteresis motor. It was shown how static and dynamic trapped field magnetisation of the rotor with YBCO rings will increase flux in the air gap motor, increasing the motor capacity to twice its original level. (orig.) [de

  19. Improved charge amplifier using hybrid hysteresis compensation

    Science.gov (United States)

    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.

  20. Gravitation Field Dynamics in Jeans Theory

    Indian Academy of Sciences (India)

    2016-01-27

    Jan 27, 2016 ... Closed system of time equations for nonrelativistic gravitation field and hydrodynamic medium was obtained by taking into account binary correlations of the field, which is the generalization of Jeans theory. Distribution function of the systemwas built on the basis of the Bogolyubov reduced description ...

  1. Goldstone bosons and a dynamical Higgs field

    NARCIS (Netherlands)

    Mooij, S.; Postma, M.

    2011-01-01

    Higgs inflation uses the gauge variant Higgs field as the inflaton. During inflation the Higgs field is displaced from its minimum, which results in associated Goldstone bosons that are apparently massive. Working in a minimally coupled U(1) toy model, we use the closed-time-path formalism to show

  2. Dynamical interplay between fluctuations, electric fields and ...

    Indian Academy of Sciences (India)

    An empirical similarity in the scaling properties of the probability distribution function (PDF) of turbulent transport has been observed in the plasma edge region in fusion plasmas. The investigation of the dynamical interplay between fluctuation in gradients, turbulent transport and radial electric fields has shown that these ...

  3. A Piecewise Hysteresis Model for a Damper of HIS System

    Directory of Open Access Journals (Sweden)

    Kaidong Tian

    2016-01-01

    Full Text Available A damper of the hydraulically interconnected suspension (HIS system, as a quarter HIS, is prototyped and its damping characteristic is tested to characterize the damping property. The force-velocity characteristic of the prototype is analyzed based on a set of testing results and accordingly a piecewise hysteresis model for the damper is proposed. The proposed equivalent parametric model consists of two parts: hysteresis model in low speed region and saturation model in high speed region which are used to describe the hysteresis phenomenon in low speed and nonhysteresis phenomenon in high speed, respectively. The parameters of the model are identified based on genetic algorithm by setting the constraints of parameters according to their physical significances and the corresponding testing results. The advantages of the model are highlighted by comparing to the nonhysteresis model and the permanent hysteresis model. The numerical simulation results are compared with the testing results to validate the accuracy and effectiveness of the proposed model. Finally, to further verify the proposed model’s wide applicability under different excitation conditions, its results are compared to the testing results in three-dimensional space. The research in this paper is significant for the dynamic analysis of the HIS vehicle.

  4. Dynamical mass generation in QED with weak magnetic fields

    International Nuclear Information System (INIS)

    Ayala, A.; Rojas, E.; Bashir, A.; Raya, A.

    2006-01-01

    We study the dynamical generation of masses for fundamental fermions in quenched quantum electrodynamics in the presence of magnetic fields using Schwinger-Dyson equations. We show that, contrary to the case where the magnetic field is strong, in the weak field limit eB << m(0)2, where m(0) is the value of the dynamically generated mass in the absence of the magnetic field, masses are generated above a critical value of the coupling and that this value is the same as in the case with no magnetic field. We carry out a numerical analysis to study the magnetic field dependence of the mass function above critical coupling and show that in this regime the dynamically generated mass and the chiral condensate for the lowest Landau level increase proportionally to (eB)2

  5. Nonequilibrium Dynamical Mean-Field Theory for Bosonic Lattice Models

    Directory of Open Access Journals (Sweden)

    Hugo U. R. Strand

    2015-03-01

    Full Text Available We develop the nonequilibrium extension of bosonic dynamical mean-field theory and a Nambu real-time strong-coupling perturbative impurity solver. In contrast to Gutzwiller mean-field theory and strong-coupling perturbative approaches, nonequilibrium bosonic dynamical mean-field theory captures not only dynamical transitions but also damping and thermalization effects at finite temperature. We apply the formalism to quenches in the Bose-Hubbard model, starting from both the normal and the Bose-condensed phases. Depending on the parameter regime, one observes qualitatively different dynamical properties, such as rapid thermalization, trapping in metastable superfluid or normal states, as well as long-lived or strongly damped amplitude oscillations. We summarize our results in nonequilibrium “phase diagrams” that map out the different dynamical regimes.

  6. Adaptive Hysteresis Band Current Control for Transformerless Single-Phase PV Inverters

    DEFF Research Database (Denmark)

    Vázquez, Gerardo; Rodriguez, Pedro; Ordoñez, Rafael

    2009-01-01

    Current control based on hysteresis algorithms are widely used in different applications, such as motion control, active filtering or active/reactive power delivery control in distributed generation systems. The hysteresis current control provides to the system a fast and robust dynamic response,...... different single-phase PV inverter topologies, by means of simulations performed with PSIM. In addition, the behavior of the thermal losses when using each control structure in such converters has been studied as well.......Current control based on hysteresis algorithms are widely used in different applications, such as motion control, active filtering or active/reactive power delivery control in distributed generation systems. The hysteresis current control provides to the system a fast and robust dynamic response......, and requires a simple implementation in standard digital signal platforms. On the other hand, the main drawback of classical hysteresis current control lies in the fact that the switching frequency is variable, as the hysteresis band is fixed. In this paper a variable band hysteresis control algorithm...

  7. Laser fields in dynamically ionized plasma structures for coherent acceleration

    CERN Document Server

    Luu-Thanh, Ph.; Pukhov, A.; Kostyukov, I.

    2015-01-01

    With the emergence of the CAN (Coherent Amplification Network) laser technology, a new scheme for direct particle acceleration in periodic plasma structures has been proposed. By using our full electromagnetic relativistic particle-in-cell (PIC) simulation code equipped with ionisation module, we simulate the laser fields dynamics in the periodic structures of different materials. We study how the dynamic ionization influences the field structure.

  8. Complex dynamics of a particle in an oscillating potential field

    Indian Academy of Sciences (India)

    Barnali Pal

    2017-07-25

    Jul 25, 2017 ... Abstract. In this paper, the classical problem of the motion of a particle in one dimension with an external time- dependent field is studied from the point of view of the dynamical system. The dynamical equations of motion of the particle are formulated. Equilibrium points of the non-oscillating systems are ...

  9. Hysteresis of magnetostructural transitions: Repeatable and non-repeatable processes

    Science.gov (United States)

    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 of magnetostructural transitions: Repeatable and non-repeatable processes

    International Nuclear Information System (INIS)

    Provenzano, Virgil; Della Torre, Edward; Bennett, Lawrence H.; ElBidweihy, Hatem

    2014-01-01

    The Gd 5 Ge 2 Si 2 alloy and the off-stoichiometric Ni 50 Mn 35 In 15 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 Gd 5 Ge 2 Si 2 and Ni 50 Mn 35 In 15 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

  11. Rotational hysteresis measurements on alumite perpendicular media

    NARCIS (Netherlands)

    van Drent, W.P.; van Drent, W.P.; Sterringa, E.R.; Sterringa, E.R.; Lodder, J.C.; Bottoni, G.; Candolfo, D.; Cecchetti, A.; Masoli, F.

    1991-01-01

    Rotational hysteresis energy loss measurements have been performed to support the analysis of the magnetization processes of Fe- and Co-alumite perpendicular recording media. Two measurement techniques gave comparable results within error limits. The rotational hysteresis integral is severly lowered

  12. Hysteresis in the phase transition of chocolate

    Science.gov (United States)

    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.

  13. Classical limit of relativistic dynamical fields

    OpenAIRE

    Hruška, Ondřej

    2013-01-01

    In this work, we summarise existing results concerning the absence of "gravitational aberration" in Einstein's general theory of relativity, i.e., the fact that the gravitational "force" points towards the instantaneous position of objects with mass, although the field propagates at the speed of light. The electromagne- tic interaction behaves similarly. Thanks to that, the classical limit with infinite speed of propagation of electricity and gravitation is a good approximation of relativisti...

  14. Dynamo mode dynamics in reversed field pinches

    Science.gov (United States)

    Fitzpatrick, Richard

    1999-11-01

    Reversed field pinches (RFPs) are unstable to multiple m=1 tearing modes, resonant in the plasma core. These ``dynamo modes'' are ultimately responsible for the dynamo action which maintains the reversal of the edge toroidal magnetic field against ohmic decay. Unfortunately, the dynamo modes also generally disrupt magnetic flux surfaces in the core, thereby strongly degrading the plasma confinement. However, recent experiments in the Madison Symmetric Torus (MST) and the Reversed Field Experiment (RFX) indicate that a well-confined RFP plasma is a possibility provided that the amplitude of the dynamo modes is controlled, and the rotation of these modes is also maintained. An analytic formalism has been developed in order to investigate the nonlinear interaction of dynamo modes with one another, with static error-fields, and with eddy currents excited in the vacuum vessel or stabilizing shell. The dynamo modes are found to couple nonlinearly to form a toroidally localized magnetic structure which can be identified as the ``slinky mode,'' reported in many RFP experiments. As the mode amplitudes increase, the slinky mode forms via a series of bifurcations in which the overall mode structure and the plasma rotation profile both change discontinuously. The threshold amplitude for the onset of these bifurcations is similar to that observed experimentally. The absence of mode rotation in RFX (which gives rise to serious edge loading problems) is shown to be due to strong eddy currents excited in the resistive vacuum vessel. Dynamo modes are slowed down by these eddy currents to such an extent that they are easily locked by small static error-fields which would otherwise (i.e., in the absence of the vacuum vessel eddy currents) be unable to affect the mode rotation. Since MST does not possess a resistive vacuum vessel (in MST the thick stabilizing shell also plays the role of the vacuum vessel: in RFX there is a separate vacuum vessel inside the shell) there are no vacuum

  15. Steering Micro-Robotic Swarm by Dynamic Actuating Fields

    NARCIS (Netherlands)

    Chao, Q.; Yu, J; Dai, C.; Xu, T; Zhang, L.; Wang, C.C.; Jin, X.

    2016-01-01

    We present a general solution for steering microrobotic
    swarm by dynamic actuating fields. In our approach, the
    motion of micro-robots is controlled by changing the actuating
    direction of a field applied to them. The time-series sequence
    of actuating field’s directions can be

  16. Dynamically orthogonal field equations for stochastic flows and particle dynamics

    Science.gov (United States)

    2011-02-01

    fields implies orthogonality of their spatial Fourier, Gabor, and Wavelet transforms [5], [35]. Therefore, different DO modes always contain different...modes stochastic solution u (x, t;ω) to the stochastic subspace computed using the five modes solution, i.e. σ2i (t) = var [〈u (x, t;ω) ,vi (x, t...Antoine, R. Murenzi, P. Vandergheynst, and S.T. Ali. Two-dimensional wavelets and their relatives. Cambridge University Press, 2004. [6] V.I. Arnold and

  17. Stabilization and Control Models of Systems With Hysteresis Nonlinearities

    Directory of Open Access Journals (Sweden)

    Mihail E. Semenov

    2012-05-01

    Full Text Available Mechanical and economic systems with hysteresis nonlinearities are studied in article. Dissipativity condition of inverted pendulum under the hysteresis control is obtained. The solution of the optimal production strategy problem was found where price has hysteresis behaviour.

  18. Dynamically important magnetic fields near accreting supermassive black holes.

    Science.gov (United States)

    Zamaninasab, M; Clausen-Brown, E; Savolainen, T; Tchekhovskoy, A

    2014-06-05

    Accreting supermassive black holes at the centres of active galaxies often produce 'jets'--collimated bipolar outflows of relativistic particles. Magnetic fields probably play a critical role in jet formation and in accretion disk physics. A dynamically important magnetic field was recently found near the Galactic Centre black hole. If this is common and if the field continues to near the black hole event horizon, disk structures will be affected, invalidating assumptions made in standard models. Here we report that jet magnetic field and accretion disk luminosity are tightly correlated over seven orders of magnitude for a sample of 76 radio-loud active galaxies. We conclude that the jet-launching regions of these radio-loud galaxies are threaded by dynamically important fields, which will affect the disk properties. These fields obstruct gas infall, compress the accretion disk vertically, slow down the disk rotation by carrying away its angular momentum in an outflow and determine the directionality of jets.

  19. High-field spin dynamics of antiferromagnetic quantum spin chains

    DEFF Research Database (Denmark)

    Enderle, M.; Regnault, L.P.; Broholm, C.

    2000-01-01

    present recent work on the high-field spin dynamics of the S = I antiferromagnetic Heisenberg chains NENP (Haldane ground state) and CsNiCl3 (quasi-1D HAF close to the quantum critical point), the uniform S = 1/2 chain CTS, and the spin-Peierls system CuGeO3. (C) 2000 Elsevier Science B,V. All rights......The characteristic internal order of macroscopic quantum ground states in one-dimensional spin systems is usually not directly accessible, but reflected in the spin dynamics and the field dependence of the magnetic excitations. In high magnetic fields quantum phase transitions are expected. We...

  20. Local hysteresis and grain size effect in Pb(Mg1/3Nb2/3)O3- PbTiO3 thin films

    Science.gov (United States)

    Shvartsman, V. V.; Emelyanov, A. Yu.; Kholkin, A. L.; Safari, A.

    2002-07-01

    The local piezoelectric properties of relaxor ferroelectric films of solid solutions 0.9Pb(Mg1/3Nb2/3)O3- 0.1PbTiO3 were investigated by scanning force microscopy (SFM) in a piezoelectric contact mode. The piezoelectric hysteresis loops were acquired in the interior of grains of different sizes. A clear correlation between the values of the effective piezoelectric coefficients, deff, and the size of the respective grains is observed. Small grains exhibit slim piezoelectric hysteresis loops with low remanent deff, whereas relatively strong piezoelectric activity is characteristic of larger grains. Part of the grains (approx20-25%) is strongly polarized without application of a dc field. The nature of both phenomena is discussed in terms of the internal bias field and grain size effects on the dynamics of nanopolar clusters.

  1. Dynamic characterization of oil fields, complex stratigraphically using genetic algorithms

    International Nuclear Information System (INIS)

    Gonzalez, Santiago; Hidrobo, Eduardo A

    2004-01-01

    A novel methodology is presented in this paper for the characterization of highly heterogeneous oil fields by integration of the oil fields dynamic information to the static updated model. The objective of the oil field's characterization process is to build an oil field model, as realistic as possible, through the incorporation of all the available information. The classical approach consists in producing a model based in the oil field's static information, having as the process final stage the validation model with the dynamic information available. It is important to clarify that the term validation implies a punctual process by nature, generally intended to secure the required coherence between productive zones and petrophysical properties. The objective of the proposed methodology is to enhance the prediction capacity of the oil field's model by previously integrating, parameters inherent to the oil field's fluid dynamics by a process of dynamic data inversion through an optimization procedure based on evolutionary computation. The proposed methodology relies on the construction of the oil field's high-resolution static model, escalated by means of hybrid techniques while aiming to preserve the oil field's heterogeneity. Afterwards, using an analytic simulator as reference, the scaled model is methodically modified by means of an optimization process that uses genetic algorithms and production data as conditional information. The process's final product is a model that observes the static and dynamic conditions of the oil field with the capacity to minimize the economic impact that generates production historical adjustments to the simulation tasks. This final model features some petrophysical properties (porosity, permeability and water saturation), as modified to achieve a better adjustment of the simulated production's history versus the real one history matching. Additionally, the process involves a slight modification of relative permeability, which has

  2. Dynamics of classical and quantum fields an introduction

    CERN Document Server

    Setlur, Girish S

    2014-01-01

    Dynamics of Classical and Quantum Fields: An Introduction focuses on dynamical fields in non-relativistic physics. Written by a physicist for physicists, the book is designed to help readers develop analytical skills related to classical and quantum fields at the non-relativistic level, and think about the concepts and theory through numerous problems. In-depth yet accessible, the book presents new and conventional topics in a self-contained manner that beginners would find useful. A partial list of topics covered includes: Geometrical meaning of Legendre transformation in classical mechanics Dynamical symmetries in the context of Noether's theorem The derivation of the stress energy tensor of the electromagnetic field, the expression for strain energy in elastic bodies, and the Navier Stokes equation Concepts of right and left movers in case of a Fermi gas explained Functional integration is interpreted as a limit of a sequence of ordinary integrations Path integrals for one and two quantum particles and for...

  3. Vector hysteresis measurements via a single disk tester

    International Nuclear Information System (INIS)

    Cardelli, E.; Faba, A.

    2006-01-01

    In this paper we present a single disk tester (SDT) developed for vector hysteresis measurements of magnetic steels. The measurement system deals with a stator of a 3-phase induction motor and some suitable magnetic field and magnetic induction probes. Numerical calculations based to a FEM approach in time domain and experimental tests are shown in order to describe both accuracy and efficiency of this measurement system

  4. Contribution for the assessment and simplified calculation of structures taking into account hysteresis evolution

    International Nuclear Information System (INIS)

    Dorka, U.E.

    1988-01-01

    By defining a scalar function of comparison in general and isolating one-dimensional cyclic hysteresis curves for field elements, the foundation is laid for a unified way of judging systems with chain-type structure taking into account hysteresis evolution. A general description of this evolution leads to certain evolutionary properties, with the 'linear' and 'uniform' evolution covering the usual methods for low-cycle fatigue (Miner's rule, Manson-Coffin, Rainflow, etc.). For the more realistic case of an 'exponential' and 'consistent' evolution, experimentally verifiable typ-functions are given which enable with fair accuracy an approximate time-domain computation of a system regarding hysteresis evolution. (orig.) [de

  5. A stochastic phase-field model determined from molecular dynamics

    KAUST Repository

    von Schwerin, Erik

    2010-03-17

    The dynamics of dendritic growth of a crystal in an undercooled melt is determined by macroscopic diffusion-convection of heat and by capillary forces acting on the nanometer scale of the solid-liquid interface width. Its modelling is useful for instance in processing techniques based on casting. The phase-field method is widely used to study evolution of such microstructural phase transformations on a continuum level; it couples the energy equation to a phenomenological Allen-Cahn/Ginzburg-Landau equation modelling the dynamics of an order parameter determining the solid and liquid phases, including also stochastic fluctuations to obtain the qualitatively correct result of dendritic side branching. This work presents a method to determine stochastic phase-field models from atomistic formulations by coarse-graining molecular dynamics. It has three steps: (1) a precise quantitative atomistic definition of the phase-field variable, based on the local potential energy; (2) derivation of its coarse-grained dynamics model, from microscopic Smoluchowski molecular dynamics (that is Brownian or over damped Langevin dynamics); and (3) numerical computation of the coarse-grained model functions. The coarse-grained model approximates Gibbs ensemble averages of the atomistic phase-field, by choosing coarse-grained drift and diffusion functions that minimize the approximation error of observables in this ensemble average. © EDP Sciences, SMAI, 2010.

  6. Dynamic polarizability of a complex atom in strong laser fields

    International Nuclear Information System (INIS)

    Rapoport, L.P.; Klinskikh, A.F.; Mordvinov, V.V.

    1997-01-01

    An asymptotic expansion of the dynamic polarizability of a complex atom in a strong circularly polarized light field is found for the case of high frequencies. The self-consistent approximation of the Hartree-Fock type for the ''atom+field'' system is developed, within the framework of which a numerical calculation of the dynamic polarizability of Ne, Kr, and Ar atoms in a strong radiation field is performed. The strong field effect is shown to manifest itself not only in a change of the energy spectrum and the character of behavior of the wave functions of atomic electrons, but also in a modification of the one-electron self-consistent potential for the atom in the field

  7. Origins and mechanisms of hysteresis in organometal halide perovskites

    Science.gov (United States)

    Li, Cheng; Guerrero, Antonio; Zhong, Yu; Huettner, Sven

    2017-05-01

    Inorganic-organic halide organometal perovskites, such as CH3NH3PbI3 and CsPbI3, etc, have been an unprecedented rising star in the field of photovoltaics since 2009, owing to their exceptionally high power conversion efficiency and simple fabrication processability. Despite its relatively short history of development, intensive investigations have been concentrating on this material; these have ranged from crystal structure analysis and photophysical characterization to performance optimization and device integration, etc. Yet, when applied in photovoltaic devices, this material suffers from hysteresis, that is, the difference of the current-voltage (I-V) curve during sweeping in two directions (from short-circuit towards open-circuit and vice versa). This behavior may significantly impede its large-scale commercial application. This Review will focus on the recent theoretical and experimental efforts to reveal the origin and mechanism of hysteresis. The proposed origins include (1) ferroelectric polarization, (2) charge trapping/detrapping, and (3) ion migration. Among them, recent evidence consistently supports the idea that ion migration plays a key role for the hysteretic behavior in perovskite solar cells (PSCs). Hence, this Review will summarize the recent results on ion migration such as the migrating ion species, activation energy measurement, capacitive characterization, and internal electrical field modulation, etc. In addition, this Review will also present the devices with alleviation/elimination of hysteresis by incorporating either large-size grains or phenyl-C61-butyric acid methyl ester molecules. In a different application, the hysteretic property has been utilized in photovoltaic and memristive switching devices. In sum, by examining these three possible mechanisms, it is concluded that the origin of hysteresis in PSCs is associated with a combination of effects, but mainly limited by ion/defect migration. This strong interaction between ion

  8. Electron Dynamics in Nanostructures in Strong Laser Fields

    Energy Technology Data Exchange (ETDEWEB)

    Kling, Matthias

    2014-09-11

    The goal of our research was to gain deeper insight into the collective electron dynamics in nanosystems in strong, ultrashort laser fields. The laser field strengths will be strong enough to extract and accelerate electrons from the nanoparticles and to transiently modify the materials electronic properties. We aimed to observe, with sub-cycle resolution reaching the attosecond time domain, how collective electronic excitations in nanoparticles are formed, how the strong field influences the optical and electrical properties of the nanomaterial, and how the excitations in the presence of strong fields decay.

  9. An estimate of energy dissipation due to soil-moisture hysteresis

    KAUST Repository

    McNamara, H.

    2014-01-01

    Processes of infiltration, transport, and outflow in unsaturated soil necessarily involve the dissipation of energy through various processes. Accounting for these energetic processes can contribute to modeling hydrological and ecological systems. The well-documented hysteretic relationship between matric potential and moisture content in soil suggests that one such mechanism of energy dissipation is associated with the cycling between wetting and drying processes, but it is challenging to estimate the magnitude of the effect in situ. The Preisach model, a generalization of the Independent Domain model, allows hysteresis effects to be incorporated into dynamical systems of differential equations. Building on earlier work using such systems with field data from the south-west of Ireland, this work estimates the average rate of hysteretic energy dissipation. Through some straightforward assumptions, the magnitude of this rate is found to be of O(10-5) W m-3. Key Points Hysteresis in soil-water dissipates energy The rate of dissipation can be estimated directly from saturation data The rate of heating caused is significant ©2013. American Geophysical Union. All Rights Reserved.

  10. Photo-assisted hysteresis of electronic transport for ZnO nanowire transistors

    Science.gov (United States)

    Du, Qianqian; Ye, Jiandong; Xu, Zhonghua; Zhu, Shunming; Tang, Kun; Gu, Shulin; Zheng, Youdou

    2018-03-01

    Recently, ZnO nanowire field effect transistors (FETs) have received renewed interest due to their extraordinary low dimensionality and high sensitivity to external chemical environments and illumination conditions. These prominent properties have promising potential in nanoscale chemical and photo-sensors. In this article, we have fabricated ZnO nanowire FETs and have found hysteresis behavior in their transfer characteristics. The mechanism and dynamics of the hysteresis phenomena have been investigated in detail by varying the sweeping rate and range of the gate bias with and without light irradiation. Significantly, light irradiation is of great importance on charge trapping by regulating adsorption and desorption of oxygen at the interface of ZnO/SiO2. Carriers excited by light irradiation can dramatically promote trapping/detrapping processes. With the assistance of light illumination, we have demonstrated a photon-assisted nonvolatile memory which employs the ZnO nanowire FET. The device exhibits reliable programming/erasing operations and a large on/off ratio. The proposed proto-type memory has thus provided a possible novel path for creating a memory functionality to other low-dimensional material systems.

  11. Review of inductively coupled plasmas: Nano-applications and bistable hysteresis physics

    Science.gov (United States)

    Lee, Hyo-Chang

    2018-03-01

    Many different gas discharges and plasmas exhibit bistable states under a given set of conditions, and the history-dependent hysteresis that is manifested by intensive quantities of the system upon variation of an external parameter has been observed in inductively coupled plasmas (ICPs). When the external parameters (such as discharge powers) increase, the plasma density increases suddenly from a low- to high-density mode, whereas decreasing the power maintains the plasma in a relatively high-density mode, resulting in significant hysteresis. To date, a comprehensive description of plasma hysteresis and a physical understanding of the main mechanism underlying their bistability remain elusive, despite many experimental observations of plasma bistability conducted under radio-frequency ICP excitation. This fundamental understanding of mode transitions and hysteresis is essential and highly important in various applied fields owing to the widespread use of ICPs, such as semiconductor/display/solar-cell processing (etching, deposition, and ashing), wireless light lamp, nanostructure fabrication, nuclear-fusion operation, spacecraft propulsion, gas reformation, and the removal of hazardous gases and materials. If, in such applications, plasma undergoes a mode transition and hysteresis occurs in response to external perturbations, the process result will be strongly affected. Due to these reasons, this paper comprehensively reviews both the current knowledge in the context of the various applied fields and the global understanding of the bistability and hysteresis physics in the ICPs. At first, the basic understanding of the ICP is given. After that, applications of ICPs to various applied fields of nano/environmental/energy-science are introduced. Finally, the mode transition and hysteresis in ICPs are studied in detail. This study will show the fundamental understanding of hysteresis physics in plasmas and give open possibilities for applications to various applied

  12. Fractional dynamics of charged particles in magnetic fields

    Science.gov (United States)

    Coronel-Escamilla, A.; Gómez-Aguilar, J. F.; Alvarado-Méndez, E.; Guerrero-Ramírez, G. V.; Escobar-Jiménez, R. F.

    2016-02-01

    In many physical applications the electrons play a relevant role. For example, when a beam of electrons accelerated to relativistic velocities is used as an active medium to generate Free Electron Lasers (FEL), the electrons are bound to atoms, but move freely in a magnetic field. The relaxation time, longitudinal effects and transverse variations of the optical field are parameters that play an important role in the efficiency of this laser. The electron dynamics in a magnetic field is a means of radiation source for coupling to the electric field. The transverse motion of the electrons leads to either gain or loss energy from or to the field, depending on the position of the particle regarding the phase of the external radiation field. Due to the importance to know with great certainty the displacement of charged particles in a magnetic field, in this work we study the fractional dynamics of charged particles in magnetic fields. Newton’s second law is considered and the order of the fractional differential equation is (0;1]. Based on the Grünwald-Letnikov (GL) definition, the discretization of fractional differential equations is reported to get numerical simulations. Comparison between the numerical solutions obtained on Euler’s numerical method for the classical case and the GL definition in the fractional approach proves the good performance of the numerical scheme applied. Three application examples are shown: constant magnetic field, ramp magnetic field and harmonic magnetic field. In the first example the results obtained show bistability. Dissipative effects are observed in the system and the standard dynamic is recovered when the order of the fractional derivative is 1.

  13. Inflationary dynamics of kinetically-coupled gauge fields

    DEFF Research Database (Denmark)

    Ferreira, Ricardo J. Z.; Ganc, Jonathan

    2015-01-01

    We investigate the inflationary dynamics of two kinetically-coupled massless U(1) gauge fields with time-varying kinetic-term coefficients. Ensuring that the system does not have strongly coupled regimes shrinks the parameter space. Also, we further restrict ourselves to systems that can be quant......We investigate the inflationary dynamics of two kinetically-coupled massless U(1) gauge fields with time-varying kinetic-term coefficients. Ensuring that the system does not have strongly coupled regimes shrinks the parameter space. Also, we further restrict ourselves to systems that can...

  14. Hysteresis Compensation of Piezoresistive Carbon Nanotube/Polydimethylsiloxane Composite-Based Force Sensors

    Directory of Open Access Journals (Sweden)

    Ji-Sik Kim

    2017-01-01

    Full Text Available This paper provides a preliminary study on the hysteresis compensation of a piezoresistive silicon-based polymer composite, poly(dimethylsiloxane dispersed with carbon nanotubes (CNTs, to demonstrate its feasibility as a conductive composite (i.e., a force-sensitive resistor for force sensors. In this study, the potential use of the nanotube/polydimethylsiloxane (CNT/PDMS as a force sensor is evaluated for the first time. The experimental results show that the electrical resistance of the CNT/PDMS composite changes in response to sinusoidal loading and static compressive load. The compensated output based on the Duhem hysteresis model shows a linear relationship. This simple hysteresis model can compensate for the nonlinear frequency-dependent hysteresis phenomenon when a dynamic sinusoidal force input is applied.

  15. A thermodynamically consistent model for magnetic hysteresis

    International Nuclear Information System (INIS)

    Ho, Kwangsoo

    2014-01-01

    A phenomenological constitutive model is presented to describe the magnetization curve within the context of thermodynamics. Due to the phenomenological analogy between the magnetic hysteresis and the stress hysteresis, the basic structure of the proposed model comes from rate-dependent plasticity in continuum mechanics, namely viscoplasticity. The total magnetic flux density is assumed to be the sum of reversible and irreversible parts. The model introduces the evolution laws of two internal state variables to incorporate the effect of the ever-changing internal microstructure on the current state. The conception originated from viscoplasticity enables the frequency dependence of the hysteresis curve to be modeled. - Highlights: • A constitutive model is proposed within the framework of thermodynamic principles. • The basic structure of formulation is originated from the rate-dependent plasticity. • Decomposition of the magnetic flux into reversible and irreversible parts is assumed. • Constitutive model reproduces the frequency dependency of magnetic hysteresis

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

    Science.gov (United States)

    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

  17. Nonlinear dynamics of semiconductors in strong THz electric fields

    DEFF Research Database (Denmark)

    Tarekegne, Abebe Tilahun

    weak THz and near infrared pulses as probes. Firstly, an intense THz pulse is used to study THz-induced impact ionization (IMI) dynamics in silicon. Local field enhancement by metallic dipole antenna arrays has been used to generate strong electric fields of several MV/cm in the hot spots near...... uniquely. Finally it is demonstrated for the first time that SiC can be tailored to have extremely fast THz-induced nonlinear behavior in moderate THz electric fields by addition of appropriate dopants. A 4H-SiC sample with high concentrations of nitrogen and boron dopants shows a nonlinear THz......In this thesis, we investigate nonlinear interactions of an intense terahertz (THz) field with semiconductors, in particular the technologically relevant materials silicon and silicon carbide. We reveal the time-resolved dynamics of the nonlinear processes by pump-probe experiments that involve...

  18. Size dependent thermal hysteresis in spin crossover nanoparticles reflected within a Monte Carlo based Ising-like model

    International Nuclear Information System (INIS)

    Atitoaie, Alexandru; Tanasa, Radu; Enachescu, Cristian

    2012-01-01

    Spin crossover compounds are photo-magnetic bistable molecular magnets with two states in thermodynamic competition: the diamagnetic low-spin state and paramagnetic high-spin state. The thermal transition between the two states is often accompanied by a wide hysteresis, premise for possible application of these materials as recording media. In this paper we study the influence of the system's size on the thermal hysteresis loops using Monte Carlo simulations based on an Arrhenius dynamics applied for an Ising like model with long- and short-range interactions. We show that using appropriate boundary conditions it is possible to reproduce both the drop of hysteresis width with decreasing particle size, the hysteresis shift towards lower temperatures and the incomplete transition, as in the available experimental data. The case of larger systems composed by several sublattices is equally treated reproducing the shrinkage of the hysteresis loop's width experimentally observed. - Highlights: ► A study concerning size effects in spin crossover nanoparticles hysteresis is presented. ► An Ising like model with short- and long-range interactions and Arrhenius dynamics is employed. ► In open boundary system the hysteresis width decreases with particle size. ► With appropriate environment, hysteresis loop is shifted towards lower temperature and transition is incomplete.

  19. Book review: old fields: dynamics and restoration of abandoned farmland

    Science.gov (United States)

    The 2007 volume, “Old Fields: Dynamics and Restoration of Abandoned Farmland”, edited by VA Cramer and RJ Hobbs and published by the Society for Ecological Restoration International (Island Press), is a valuable attempt to synthesize a dozen case studies on agricultural abandonment from all of the ...

  20. Local field corrections in the lattice dynamics of chromium | Ndukwe ...

    African Journals Online (AJOL)

    This work extends the inclusion of local field corrections in the calculation of the phonon dispersion curves to the transition metal, chromium (Cr3+) using the formalism of lattice dynamics based on the transition metal model potential approach in the adiabatic and hatmonic approximations. The results obtained here have a ...

  1. Field and Laboratory Evaluation of Dynamics in Soil Properties of ...

    African Journals Online (AJOL)

    Dynamics in properties of soils of three land use types (Fallow, Pineapple and Cassava) in Owerri, Southeastern Nigeria were evaluated under field and laboratory incubation conditions. Soil properties varied with time within land use types, with chemical more significantly than physical properties under both conditions.

  2. Dynamic Incentive Effects of Relative Performance Pay: A Field Experiment

    NARCIS (Netherlands)

    J. Delfgaauw (Josse); A.J. Dur (Robert); J.A. Non (Arjan); W.J.M.I. Verbeke (Willem)

    2010-01-01

    textabstractWe conduct a field experiment among 189 stores of a retail chain to study dynamic incentive effects of relative performance pay. Employees in the randomly selected treatment stores could win a bonus by outperforming three comparable stores from the control group over the course of four

  3. Dynamics of Deformable Active Particles under External Flow Field

    Science.gov (United States)

    Tarama, Mitsusuke

    2017-10-01

    In most practical situations, active particles are affected by their environment, for example, by a chemical concentration gradient, light intensity, gravity, or confinement. In particular, the effect of an external flow field is important for particles swimming in a solvent fluid. For deformable active particles such as self-propelled liquid droplets and active vesicles, as well as microorganisms such as euglenas and neutrophils, a general description has been developed by focusing on shape deformation. In this review, we present our recent studies concerning the dynamics of a single active deformable particle under an external flow field. First, a set of model equations of active deformable particles including the effect of a general external flow is introduced. Then, the dynamics under two specific flow profiles is discussed: a linear shear flow, as the simplest example, and a swirl flow. In the latter case, the scattering dynamics of the active deformable particles by the swirl flow is also considered.

  4. Stability analysis and controller design for a linear system with Duhem hysteresis nonlinearity

    NARCIS (Netherlands)

    Ouyang, Ruiyue; Jayawardhana, Bayu

    2012-01-01

    In this paper, we investigate the stability of feedback interconnections between a linear system and a Duhem hysteresis operator, where the linear system satisfies either counter-clockwise (CCW) or clockwise (CW) inputoutput dynamics [1], [13]. More precisely, depending on the input-output dynamics

  5. The Zimanyi and Moszkowski model in thermo field dynamics

    International Nuclear Information System (INIS)

    Aguirre, R.; Civitarese, O.; Paoli, A.L. de

    1996-01-01

    The effective Lagrangian introduced by Zimanyi and Moszkowski is used to calculate the equation of state of symmetric nuclear matter at finite densities and temperatures. The model is treated in the mean field approximation and one-loop perturbative corrections are added to the mean field value of relevant propagators. Green functions for baryons and mesons are constructed in the framework of thermo field dynamics. An effective residual interaction, with coupling coefficients which are dependent on density and temperature, is introduced. This effective coupling is used to calculate perturbative corrections to the baryon mass, the equation of state and the compressibility of the system. (orig.)

  6. Approximate photochemical dynamics of azobenzene with reactive force fields

    Science.gov (United States)

    Li, Yan; Hartke, Bernd

    2013-12-01

    We have fitted reactive force fields of the ReaxFF type to the ground and first excited electronic states of azobenzene, using global parameter optimization by genetic algorithms. Upon coupling with a simple energy-gap transition probability model, this setup allows for completely force-field-based simulations of photochemical cis→trans- and trans→cis-isomerizations of azobenzene, with qualitatively acceptable quantum yields. This paves the way towards large-scale dynamics simulations of molecular machines, including bond breaking and formation (via the reactive force field) as well as photochemical engines (presented in this work).

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

    International Nuclear Information System (INIS)

    Kocakaplan, Yusuf; Keskin, Mustafa

    2014-01-01

    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

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

    Energy Technology Data Exchange (ETDEWEB)

    Kocakaplan, Yusuf [Graduate School of Natural and Applied Sciences, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    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.

  9. Hysteresis in the transfer characteristics of MoS2 transistors

    Science.gov (United States)

    Di Bartolomeo, Antonio; Genovese, Luca; Giubileo, Filippo; Iemmo, Laura; Luongo, Giuseppe; Foller, Tobias; Schleberger, Marika

    2018-01-01

    We investigate the origin of the hysteresis observed in the transfer characteristics of back-gated field-effect transistors with an exfoliated MoS2 channel. We find that the hysteresis is strongly enhanced by increasing either gate voltage, pressure, temperature or light intensity. Our measurements reveal a step-like behavior of the hysteresis around room temperature, which we explain as water-facilitated charge trapping at the MoS2/SiO2 interface. We conclude that intrinsic defects in MoS2, such as S vacancies, which result in effective positive charge trapping, play an important role, besides H2O and O2 adsorbates on the unpassivated device surface. We show that the bistability associated to the hysteresis can be exploited in memory devices.

  10. Field quality issues in iron-dominated dipoles at low fields

    International Nuclear Information System (INIS)

    Brown, B.C.

    1996-10-01

    In order to help assess the usable dynamic range of iron-dominated dipoles, field shape data at low field on several Fermi-lab accelerator dipole designs are presented. Emphasis is placed on the systematic and random values of the low field sextupole since it is the first ''allowed'' field error. The Main Injector dipoles provide four times smaller sextupole and more than 20 times less sextupole hysteresis than earlier designs for the Main Ring

  11. Dynamics of molecular superrotors in an external magnetic field

    Science.gov (United States)

    Korobenko, Aleksey; Milner, Valery

    2015-08-01

    We excite diatomic oxygen and nitrogen to high rotational states with an optical centrifuge and study their dynamics in an external magnetic field. Ion imaging is employed to directly visualize, and follow in time, the rotation plane of the molecular superrotors. The two different mechanisms of interaction between the magnetic field and the molecular angular momentum in paramagnetic oxygen and non-magnetic nitrogen lead to qualitatively different behaviour. In nitrogen, we observe the precession of the molecular angular momentum around the field vector. In oxygen, strong spin-rotation coupling results in faster and richer dynamics, encompassing the splitting of the rotation plane into three separate components. As the centrifuged molecules evolve with no significant dispersion of the molecular wave function, the observed magnetic interaction presents an efficient mechanism for controlling the plane of molecular rotation.

  12. Dynamics of molecular superrotors in an external magnetic field

    International Nuclear Information System (INIS)

    Korobenko, Aleksey; Milner, Valery

    2015-01-01

    We excite diatomic oxygen and nitrogen to high rotational states with an optical centrifuge and study their dynamics in an external magnetic field. Ion imaging is employed to directly visualize, and follow in time, the rotation plane of the molecular superrotors. The two different mechanisms of interaction between the magnetic field and the molecular angular momentum in paramagnetic oxygen and non-magnetic nitrogen lead to qualitatively different behaviour. In nitrogen, we observe the precession of the molecular angular momentum around the field vector. In oxygen, strong spin–rotation coupling results in faster and richer dynamics, encompassing the splitting of the rotation plane into three separate components. As the centrifuged molecules evolve with no significant dispersion of the molecular wave function, the observed magnetic interaction presents an efficient mechanism for controlling the plane of molecular rotation. (paper)

  13. First principles molecular dynamics without self-consistent field optimization

    International Nuclear Information System (INIS)

    Souvatzis, Petros; Niklasson, Anders M. N.

    2014-01-01

    We present a first principles molecular dynamics approach that is based on time-reversible extended Lagrangian Born-Oppenheimer molecular dynamics [A. M. N. Niklasson, Phys. Rev. Lett. 100, 123004 (2008)] in the limit of vanishing self-consistent field optimization. The optimization-free dynamics keeps the computational cost to a minimum and typically provides molecular trajectories that closely follow the exact Born-Oppenheimer potential energy surface. Only one single diagonalization and Hamiltonian (or Fockian) construction are required in each integration time step. The proposed dynamics is derived for a general free-energy potential surface valid at finite electronic temperatures within hybrid density functional theory. Even in the event of irregular functional behavior that may cause a dynamical instability, the optimization-free limit represents a natural starting guess for force calculations that may require a more elaborate iterative electronic ground state optimization. Our optimization-free dynamics thus represents a flexible theoretical framework for a broad and general class of ab initio molecular dynamics simulations

  14. Hysteresis response of daytime net ecosystem exchange during drought

    Directory of Open Access Journals (Sweden)

    N. Pingintha

    2010-03-01

    Full Text Available Continuous measurements of net ecosystem CO2 exchange (NEE using the eddy-covariance method were made over an agricultural ecosystem in the southeastern US. During optimum environmental conditions, photosynthetically active radiation (PAR was the primary driver controlling daytime NEE, accounting for as much as 67 to 89% of the variation in NEE. However, soil water content became the dominant factor limiting the NEE-PAR response during the peak growth stage. NEE was significantly depressed when high PAR values coincided with very low soil water content. The presence of a counter-clockwise hysteresis of daytime NEE with PAR was observed during periods of water stress. This is a result of the stomatal closure control of photosynthesis at high vapor pressure deficit and enhanced respiration at high temperature. This result is significant since this hysteresis effect limits the range of applicability of the Michaelis-Menten equation and other related expressions in the determination of daytime NEE as a function of PAR. The systematic presence of hysteresis in the response of NEE to PAR suggests that the gap-filling technique based on a non-linear regression approach should take into account the presence of water-limited field conditions. Including this step is therefore likely to improve current evaluation of ecosystem response to increased precipitation variability arising from climatic changes.

  15. Dynamics of dissociation versus ionization in strong laser fields

    International Nuclear Information System (INIS)

    In this paper, experimental results are presented which clearly demonstrate the effectiveness that an external field has in altering the dissociation dynamics. The experiment examines the strong-field dissociation dynamics of molecular hydrogen ions and its deuterated isotopes. These studies involve multiphoton excitation in the intensity regime of 10 11-14 W/cm 2 with the fundamental and second harmonic of a ND:YAG or ND:YLF laser system. Measurements include energy resolved electron and mass spectroscopy which provide useful probes in elucidating the interaction dynamics predicted by existing models. The example this in this paper, examines the strong-field dissociation of H 2 + , HD + , and D 2 + at green (0.5 μm) and (1μm) frequencies. The diatomic ions are formed via multiphonon ionization of the neutral precursor which is physically separable from the dissociation process. This study provides the first observation of the dynamics associated with the above threshold dissociation (ATD) process and analogies will be made with the more familiar above threshold ionization (ATI) phenomenon

  16. Modeling and inverse feedforward control for conducting polymer actuators with hysteresis

    International Nuclear Information System (INIS)

    Wang, Xiangjiang; Alici, Gursel; Tan, Xiaobo

    2014-01-01

    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. (paper)

  17. Dynamic Neural Fields as a Step Towards Cognitive Neuromorphic Architectures

    Directory of Open Access Journals (Sweden)

    Yulia eSandamirskaya

    2014-01-01

    Full Text Available Dynamic Field Theory (DFT is an established framework for modelling embodied cognition. In DFT, elementary cognitive functions such as memory formation, formation of grounded representations, attentional processes, decision making, adaptation, and learning emerge from neuronal dynamics. The basic computational element of this framework is a Dynamic Neural Field (DNF. Under constraints on the time-scale of the dynamics, the DNF is computationally equivalent to a soft winner-take-all (WTA network, which is considered one of the basic computational units in neuronal processing. Recently, it has been shown how a WTA network may be implemented in neuromorphic hardware, such as analogue Very Large Scale Integration (VLSI device. This paper leverages the relationship between DFT and soft WTA networks to systematically revise and integrate established DFT mechanisms that have previously been spread among different architectures. In addition, I also identify some novel computational and architectural mechanisms of DFT which may be implemented in neuromorphic VLSI devices using WTA networks as an intermediate computational layer. These specific mechanisms include the stabilization of working memory, the coupling of sensory systems to motor dynamics, intentionality, and autonomous learning. I further demonstrate how all these elements may be integrated into a unified architecture to generate behavior and autonomous learning.

  18. Simultaneous Electromagnetic Tracking and Calibration for Dynamic Field Distortion Compensation.

    Science.gov (United States)

    Sadjadi, Hossein; Hashtrudi-Zaad, Keyvan; Fichtinger, Gabor

    2016-08-01

    Electromagnetic (EM) tracking systems are highly susceptible to field distortion. The interference can cause measurement errors up to a few centimeters in clinical environments, which limits the reliability of these systems. Unless corrected for, this measurement error imperils the success of clinical procedures. It is therefore fundamental to dynamically calibrate EM tracking systems and compensate for measurement error caused by field distorting objects commonly present in clinical environments. We propose to combine a motion model with observations of redundant EM sensors and compensate for field distortions in real time. We employ a simultaneous localization and mapping technique to accurately estimate the pose of the tracked instrument while creating the field distortion map. We conducted experiments with six degrees-of-freedom motions in the presence of field distorting objects in research and clinical environments. We applied our approach to improve the EM tracking accuracy and compared our results to a conventional sensor fusion technique. Using our approach, the maximum tracking error was reduced by 67% for position measurements and by 64% for orientation measurements. Currently, clinical applications of EM trackers are hampered by the adverse distortion effects. Our approach introduces a novel method for dynamic field distortion compensation, independent from preoperative calibrations or external tracking devices, and enables reliable EM navigation for potential applications.

  19. Dynamical anisotropic response of black phosphorus under magnetic field

    Science.gov (United States)

    Liu, Xuefeng; Lu, Wei; Zhou, Xiaoying; Zhou, Yang; Zhang, Chenglong; Lai, Jiawei; Ge, Shaofeng; Sekhar, M. Chandra; Jia, Shuang; Chang, Kai; Sun, Dong

    2018-04-01

    Black phosphorus (BP) has emerged as a promising material candidate for next generation electronic and optoelectronic devices due to its high mobility, tunable band gap and highly anisotropic properties. In this work, polarization resolved ultrafast mid-infrared transient reflection spectroscopy measurements are performed to study the dynamical anisotropic optical properties of BP under magnetic fields up to 9 T. The relaxation dynamics of photoexcited carrier is found to be insensitive to the applied magnetic field due to the broadening of the Landau levels and large effective mass of carriers. While the anisotropic optical response of BP decreases with increasing magnetic field, its enhancement due to the excitation of hot carriers is similar to that without magnetic field. These experimental results can be well interpreted by the magneto-optical conductivity of the Landau levels of BP thin film, based on an effective k · p Hamiltonian and linear response theory. These findings suggest attractive possibilities of multi-dimensional control of anisotropic response (AR) of BP with light, electric and magnetic field, which further introduces BP to the fantastic magnetic field sensitive applications.

  20. Fractional Dynamics Applications of Fractional Calculus to Dynamics of Particles, Fields and Media

    CERN Document Server

    Tarasov, Vasily E

    2010-01-01

    "Fractional Dynamics: Applications of Fractional Calculus to Dynamics of Particles, Fields and Media" presents applications of fractional calculus, integral and differential equations of non-integer orders in describing systems with long-time memory, non-local spatial and fractal properties. Mathematical models of fractal media and distributions, generalized dynamical systems and discrete maps, non-local statistical mechanics and kinetics, dynamics of open quantum systems, the hydrodynamics and electrodynamics of complex media with non-local properties and memory are considered. This book is intended to meet the needs of scientists and graduate students in physics, mechanics and applied mathematics who are interested in electrodynamics, statistical and condensed matter physics, quantum dynamics, complex media theories and kinetics, discrete maps and lattice models, and nonlinear dynamics and chaos. Dr. Vasily E. Tarasov is a Senior Research Associate at Nuclear Physics Institute of Moscow State University and...

  1. Dynamic Phase Transitions In The Spin-2 Ising System Under An Oscillating Magnetic Field Within The Effective-Field Theory

    International Nuclear Information System (INIS)

    Ertas, Mehmet; Keskin, Mustafa; Deviren, Bayram

    2010-01-01

    The dynamic phase transitions are studied in the spin-2 Ising model under a time-dependent oscillating magnetic field by using the effective-field theory with correlations. The effective-field dynamic equation is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic order parameter and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are presented in (T/zJ, h/zJ) plane.

  2. Slow dynamics at critical points: the field-theoretical perspective

    International Nuclear Information System (INIS)

    Gambassi, Andrea

    2006-01-01

    The dynamics at a critical point provides a simple instance of slow collective evolution, characterised by aging phenomena and by a violation of the fluctuation-dissipation relation even for long times. By virtue of the universality in critical phenomena it is possible to provide quantitative predictions for some aspects of these behaviours by field-theoretical methods. We review some of the theoretical results that have been obtained in recent years for the relevant (universal) quantities, such as the fluctuation-dissipation ratio, associated with the non-equilibrium critical dynamics

  3. Comparison between 3D dynamics filter technique, field-in-field, electronic compensator in breast cancer

    International Nuclear Information System (INIS)

    Trindade, Cassia; Silva, Leonardo P.; Martins, Lais P.; Garcia, Paulo L.; Santos, Maira R.; Bastista, Delano V.S.; Vieira, Anna Myrian M.T.L.; Rocha, Igor M.

    2012-01-01

    The radiotherapy has been used in a wild scale in breast cancer treatment. With this high demand, new technologies have been developed to improve the dose distribution in the target while reducing the dose delivered in critical organs. In this study, performed with one clinical case, three planning were done for comparison: 3D technique with dynamic filter, 3D with field-in-field technique (forward-planned IMRT) and 3D technique using electronic compensator (ECOMP). The planning were done with a 6MV photon beam using the Eclipse software, version 8.6 (Varian Medical Systems). The PTV was drawn covering the whole breast and the critical organs were: the lung on the irradiated side, the heart, the contralateral breast and the anterior descending coronary artery (LAD). The planning using the compensator technique permitted more homogeneous dose distribution in the target volume. The V20 value of the lung on the irradiated side was 8,3% for the electronic compensator technique, 8,9% for the field-in-field technique and 8,2% for the dynamic filter technique. For the heart the dose range was 15.7 - 139.9 cGy, 16.3 - 148.4 cGy for the dynamic filter technique and 19.6 - 157.0 cGy for the field-in-field technique. The dose gradient was 11% with compensator electronic, 15% dynamic filter technique and 13% with field-in-field. The application of electronic technique in breast cancer treatment allows better dose distribution while reduces dose in critical organs, but in the same time requires a quality assurance. (author)

  4. Shapes and dynamics from the time-dependent mean field

    International Nuclear Information System (INIS)

    Stevenson, P.D.; Goddard, P.M.; Rios, A.

    2015-01-01

    Explaining observed properties in terms of underlying shape degrees of freedom is a well-established prism with which to understand atomic nuclei. Self-consistent mean-field models provide one tool to understand nuclear shapes, and their link to other nuclear properties and observables. We present examples of how the time-dependent extension of the mean-field approach can be used in particular to shed light on nuclear shape properties, particularly looking at the giant resonances built on deformed nuclear ground states, and at dynamics in highly-deformed fission isomers. Example calculations are shown of 28 Si in the first case, and 240 Pu in the latter case

  5. Strong-field short-pulse nondipole dynamics

    DEFF Research Database (Denmark)

    Dimitrovski, Darko; Førre, Morten; Madsen, Lars Bojer

    2009-01-01

    We present a quantitative investigation of strong-field short-pulse nondipole dynamics in laser-matter interactions. We find excellent agreement between ab initio numerical and analytic results obtained using the Magnus expansion. We show that in the short-pulse limit, ultrafast transfer and cont......We present a quantitative investigation of strong-field short-pulse nondipole dynamics in laser-matter interactions. We find excellent agreement between ab initio numerical and analytic results obtained using the Magnus expansion. We show that in the short-pulse limit, ultrafast transfer...... and control of population can be achieved using nondipole effects. The relative importance of nondipole to dipole effects depends on the displacement imparted to a free classical electron....

  6. Dissociation dynamics of diatomic molecules in intense fields

    Science.gov (United States)

    Magrakvelidze, Maia

    We study the dynamics of diatomic molecules (dimers) in intense IR and XUV laser fields theoretically and compare the results with measured data in collaboration with different experimental groups worldwide. The first three chapters of the thesis cover the introduction and the background on solving time-independent and time-dependent Schrodinger equation. The numerical results in this thesis are presented in four chapters, three of which are focused on diatomic molecules in IR fields. The last one concentrates on diatomic molecules in XUV pulses. The study of nuclear dynamics of H2 or D2 molecules in IR pulses is given in Chapter 4. First, we investigate the optimal laser parameters for observing field-induced bond softening and bond hardening in D2+. Next, the nuclear dynamics of H2 + molecular ions in intense laser fields are investigated by analyzing their fragment kinetic-energy release (KER) spectra as a function of the pump-probe delay τ Lastly, the electron localization is studied for long circularly polarized laser pulses. Chapter 5 covers the dissociation dynamics of O2+ in an IR laser field. The fragment KER spectra are analyzed as a function of the pump-probe delay τ Within the Born-Oppenheimer approximation, we calculate ab-initio adiabatic potential-energy curves and their electric dipole couplings, using the quantum chemistry code GAMESS. In Chapter 6, the dissociation dynamics of the noble gas dimer ions He 2+, Ne2+, Ar2 +, Kr2+, and Xe2 + is investigated in ultrashort pump and probe laser pulses of different wavelengths. We observe a striking "delay gap" in the pump-probe-delay-dependent KER spectrum only if the probe-pulse wavelength exceeds the pump-pulse wavelength. Comparing pump-probe-pulse-delay dependent KER spectra for different noble gas dimer cations, we quantitatively discuss quantum-mechanical versus classical aspects of the nuclear vibrational motion as a function of the nuclear mass. Chapter 7 focuses on diatomic molecules in XUV

  7. Hysteresis losses of magnetic nanoparticle powders in the single domain size range

    International Nuclear Information System (INIS)

    Dutz, S.; Hergt, R.; Muerbe, J.; Mueller, R.; Zeisberger, M.; Andrae, W.; Toepfer, J.; Bellemann, M.E.

    2007-01-01

    Magnetic iron oxide nanoparticle powders were investigated in order to optimise the specific hysteresis losses for biomedical heating applications. Different samples with a mean particle size in the transition range from superparamagnetic to ferromagnetic behaviour (i.e. 10-100 nm) were prepared by two different chemical precipitation routes. Additionally, the influence of milling and annealing on hysteresis losses of the nanoparticles was investigated. Structural investigations of the samples were carried out by X-ray diffraction, measurement of specific surface area, and scanning and transmission electron microscopy. The dependence of hysteresis losses of minor loops on the field amplitude was determined using vibrating sample magnetometry and caloric measurements. For small field amplitudes, a power law was found which changes into saturation at amplitudes well above the coercive field. Maximum hysteresis losses of 6.6 J/kg per cycle were observed for milled powder. For field amplitudes below about 10 kA/m, which are especially interesting for medical and technical applications, hysteresis losses of all investigated powders were at least by one order of magnitude lower than reported for magnetosomes of comparable size

  8. Gravitation Field Calculations on a Dynamic Lattice by Distributed Computing

    Science.gov (United States)

    Mähönen, Petri; Punkka, Veikko

    A new method of calculating numerically time evolution of a gravitational field in General Relatity is introduced. Vierbein (tetrad) formalism, dynamic lattice and massively parallelized computation are suggested as they are expected to speed up the calculations considerably and facilitate the solution of problems previously considered too hard to be solved, such as the time evolution of a system consisting of two or more black holes or the structure of worm holes.

  9. Gravitational field calculations on a dynamic lattice by distributed computing.

    Science.gov (United States)

    Mähönen, P.; Punkka, V.

    A new method of calculating numerically time evolution of a gravitational field in general relativity is introduced. Vierbein (tetrad) formalism, dynamic lattice and massively parallelized computation are suggested as they are expected to speed up the calculations considerably and facilitate the solution of problems previously considered too hard to be solved, such as the time evolution of a system consisting of two or more black holes or the structure of worm holes.

  10. Developing Dynamic Field Theory Architectures for Embodied Cognitive Systems withcedar.

    Science.gov (United States)

    Lomp, Oliver; Richter, Mathis; Zibner, Stephan K U; Schöner, Gregor

    2016-01-01

    Embodied artificial cognitive systems, such as autonomous robots or intelligent observers, connect cognitive processes to sensory and effector systems in real time. Prime candidates for such embodied intelligence are neurally inspired architectures. While components such as forward neural networks are well established, designing pervasively autonomous neural architectures remains a challenge. This includes the problem of tuning the parameters of such architectures so that they deliver specified functionality under variable environmental conditions and retain these functions as the architectures are expanded. The scaling and autonomy problems are solved, in part, by dynamic field theory (DFT), a theoretical framework for the neural grounding of sensorimotor and cognitive processes. In this paper, we address how to efficiently build DFT architectures that control embodied agents and how to tune their parameters so that the desired cognitive functions emerge while such agents are situated in real environments. In DFT architectures, dynamic neural fields or nodes are assigned dynamic regimes, that is, attractor states and their instabilities, from which cognitive function emerges. Tuning thus amounts to determining values of the dynamic parameters for which the components of a DFT architecture are in the specified dynamic regime under the appropriate environmental conditions. The process of tuning is facilitated by the software framework cedar , which provides a graphical interface to build and execute DFT architectures. It enables to change dynamic parameters online and visualize the activation states of any component while the agent is receiving sensory inputs in real time. Using a simple example, we take the reader through the workflow of conceiving of DFT architectures, implementing them on embodied agents, tuning their parameters, and assessing performance while the system is coupled to real sensory inputs.

  11. Equivalent Circuit Modeling of Hysteresis Motors

    Energy Technology Data Exchange (ETDEWEB)

    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.

  12. Understanding the physics that causes hysteresis in carbon nanotube transistors, a key step toward high performance and energy-efficiency

    Science.gov (United States)

    Park, Rebecca

    Three-dimensional (3D) integration is a promising technology that achieves higher energy efficiency, higher performance, and smaller footprint than today's planar, 2D technology. In particular, carbon nanotube field-effect transistors (CNFETs) enable monolithic 3D integration due to its low-temperature processing (digital systems, large hysteresis has long remained a challenge. Our approach to eliminating hysteresis is based on our understanding of the physics that lead to hysteresis: Understanding the sources of hysteresis: We develop a novel measurement technique called the Pulsed Time-Domain Measurement (PTDM) which enables quantification of charged traps responsible for hysteresis. Leveraging a physics-based model, we study the mechanism of the charge trapping process. Eliminating hysteresis: After gaining a deeper understanding of the sources of hysteresis, we are able to develop a VLSI-compatible, solid-state fabrication method that mitigates the effect of traps. On average, we achieve hysteresis of less than 0.5% of the gate-source voltage sweep range.

  13. Dynamic scattering theory for dark-field electron holography of 3D strain fields.

    Science.gov (United States)

    Lubk, Axel; Javon, Elsa; Cherkashin, Nikolay; Reboh, Shay; Gatel, Christophe; Hÿtch, Martin

    2014-01-01

    Dark-field electron holography maps strain in crystal lattices into reconstructed phases over large fields of view. Here we investigate the details of the lattice strain-reconstructed phase relationship by applying dynamic scattering theory both analytically and numerically. We develop efficient analytic linear projection rules for 3D strain fields, facilitating a straight-forward calculation of reconstructed phases from 3D strained materials. They are used in the following to quantify the influence of various experimental parameters like strain magnitude, specimen thickness, excitation error and surface relaxation. © 2013 Elsevier B.V. All rights reserved.

  14. A Simple Magnetostatic Sensing Method for Assessing the Local Hysteresis Properties in Ferromagnetic Sheet Materials

    Directory of Open Access Journals (Sweden)

    Ivan J. Garshelis

    2012-01-01

    Full Text Available Global hysteretic properties of electrical steels can be measured using ring or strip samples, while the assessment of the local hysteretic properties is a much more difficult task since the measurement method needs to be very sensitive. This paper presents a new method wherein the intensity and spatial distribution of the magnetic field, arising from large gradients in the local magnetization, are measured. These large gradients are induced by the passage of a test sample through the steep gradient field of a small, proximate permanent magnet. Magnetic field measurements during both directions of motion provide information indicative of the hysteresis properties. We theoretically analyze these measurements and show experimentally that the measurements correlate well with all the significant aspects of conventional hysteresis loops. The results given in this paper are qualitative, and the method is both by its simplicity and its sensitivity to important hysteresis features a powerful means of magnetic nondestructive evaluation.

  15. Hysteresis in mesoscopic superconducting disks: The Bean-Livingston barrier

    Science.gov (United States)

    Singha Deo, P.; Schweigert, V. A.; Peeters, F. M.

    1999-03-01

    Depending on the size of mesoscopic superconducting disks, the magnetization can show hysteretic behavior which we explain by using the Ginzburg-Landau (GL) theory and properly taking into account the demagnetization effects due to geometrical form factors. In large disks the hysteresis is due to the Bean-Livingston surface barrier while in small disks it is the volume barrier which is responsible for it. Although the sample magnetization is diamagnetic (negative) we show that the measured magnetization can be positive at certain fields as observed experimentally and which is a consequence of both the demagnetization effect and the experimental setup.

  16. A novel variable field system for field-cycled dynamic nuclear polarization spectroscopy

    Science.gov (United States)

    Shet, Keerthi; Caia, George L.; Kesselring, Eric; Samouilov, Alexandre; Petryakov, Sergey; Lurie, David J.; Zweier, Jay L.

    2010-08-01

    Dynamic nuclear polarization (DNP) is an NMR-based technique which enables detection and spectral characterization of endogenous and exogenous paramagnetic substances measured via transfer of polarization from the saturated unpaired electron spin system to the NMR active nuclei. A variable field system capable of performing DNP spectroscopy with NMR detection at any magnetic field in the range 0-0.38 T is described. The system is built around a clinical open-MRI system. To obtain EPR spectra via DNP, partial cancellation of the detection field B0NMR is required to alter the evolution field B0EPR at which the EPR excitation is achieved. The addition of resistive actively shielded field cancellation coils in the gap of the primary magnet provides this field offset in the range of 0-100 mT. A description of the primary magnet, cancellation coils, power supplies, interfacing hardware, RF electronics and console are included. Performance of the instrument has been evaluated by acquiring DNP spectra of phantoms with aqueous nitroxide solutions (TEMPOL) at three NMR detection fields of 97 G, 200 G and 587 G corresponding to 413 kHz, 851.6 kHz and 2.5 MHz respectively and fixed EPR evolution field of 100 G corresponding to an irradiation frequency of 282.3 MHz. This variable-field DNP system offers great flexibility for the performance of DNP spectroscopy with independent optimum choice of EPR excitation and NMR detection fields.

  17. Dynamics of levitated objects in acoustic vortex fields.

    Science.gov (United States)

    Hong, Z Y; Yin, J F; Zhai, W; Yan, N; Wang, W L; Zhang, J; Drinkwater, Bruce W

    2017-08-02

    Acoustic levitation in gaseous media provides a tool to process solid and liquid materials without the presence of surfaces such as container walls and hence has been used widely in chemical analysis, high-temperature processing, drop dynamics and bioreactors. To date high-density objects can only be acoustically levitated in simple standing-wave fields. Here we demonstrate the ability of a small number of peripherally placed sources to generate acoustic vortex fields and stably levitate a wide range of liquid and solid objects. The forces exerted by these acoustic vortex fields on a levitated water droplet are observed to cause a controllable deformation of the droplet and/or oscillation along the vortex axis. Orbital angular momentum transfer is also shown to rotate a levitated object rapidly and the rate of rotation can be controlled by the source amplitude. We expect this research can increase the diversity of acoustic levitation and expand the application of acoustic vortices.

  18. Measurement of dynamic magnetization induced by a pulsed field: Proposal for a new rock magnetism method

    Directory of Open Access Journals (Sweden)

    Kazuto eKodama

    2015-02-01

    Full Text Available This study proposes a new method for measuring transient magnetization of natural samples induced by a pulsed field with duration of 11 ms using a pulse magnetizer. An experimental system was constructed, consisting of a pair of differential sensing coils connected with a high-speed digital oscilloscope for data acquisition. The data were transferred to a computer to obtain an initial magnetization curve and a descending branch of a hysteresis loop in a rapidly changing positive field. This system was tested with synthetic samples (permalloy ribbon, aluminum plate, and nickel powder as well as two volcanic rock samples. Results from the synthetic samples showed considerable differences from those measured by a quasi-static method using a vibrating sample magnetometer (VSM. These differences were principally due to the time-dependent magnetic properties or to electromagnetic effects, such as magnetic viscosity, eddy current loss, or magnetic relaxation. Results from the natural samples showed that the transient magnetization–field curves were largely comparable to the corresponding portions of the hysteresis loops. However, the relative magnetization (scaled to the saturation magnetization at the end of a pulse was greater than that measured by a VSM. This discrepancy, together with the occurrence of rapid exponential decay after a pulse, indicates magnetic relaxations that could be interpreted in terms of domain wall displacement. These results suggest that with further developments, the proposed technique can become a useful tool for characterizing magnetic particles contained in a variety of natural materials.

  19. Hysteresis and transition in swirling nonpremixed flames

    NARCIS (Netherlands)

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

    2009-01-01

    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

  20. Managing Hysteresis: Three Cornerstones to Fiscal Stability

    Science.gov (United States)

    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…

  1. Weak differentiability of scalar hysteresis operators

    Czech Academy of Sciences Publication Activity Database

    Brokate, M.; Krejčí, Pavel

    2015-01-01

    Roč. 35, č. 6 (2015), s. 2405-2421 ISSN 1078-0947 R&D Projects: GA ČR GAP201/10/2315 Institutional support: RVO:67985840 Keywords : hysteresis * differentiability * variational inequality Subject RIV: BA - General Mathematics Impact factor: 1.127, year: 2015 http://www.aimsciences.org/journals/displayArticlesnew.jsp?paperID=10677

  2. A Sorption Hysteresis Model For Cellulosic Materials

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Damkilde, Lars

    2006-01-01

    The equilibrium concentration of adsorbed water in cellulosic materials is dependent on the history of the variations of vapor pressure in the ambient air, i.e. sorption hysteresis. Existing models to describe this phenomenon such as the independent domain theory have numerical drawbacks and/or i...

  3. Effect of electrostatic field on dynamic friction coefficient of pistachio

    Directory of Open Access Journals (Sweden)

    M. H Aghkhani

    2016-04-01

    Full Text Available Introduction: Separation and grading of agricultural products from the production to supply, has notable importance. The separation can be done based on physical, electrical, magnetic, optical properties and etc. It is necessary for any development of new systems to study enough on the properties and behavior of agricultural products. Some characteristics for separation are size (length, width and thickness, hardness, shape, density, surface roughness, color, speed limit, aerodynamic properties, electrical conductivity, elasticity and coefficient of static friction point. So far, the friction properties of agricultural products used in the separating process, but the effect of electrostatic charging on static and dynamic coefficients of friction for separation had little attention. The aim of this study was to find out the interactions between electrostatic and friction properties to find a way to separate products that separation is not possible with conventional methods or not sufficiently accurate. In this paper, the separation of close and smiley pistachios by electrostatic charging was investigated. Materials and Methods: Kallehghoochi pistachio cultivar has the top rank in production in Iran. Therefore, it was used as a sample. The experimental design that used in this study, had moisture content at three levels (24.2, 14.5 and 8.1 percent, electric field intensity at three levels (zero, 4000 and 7000 V, speed of movement on the surface at three levels (1300, 2500 and 3300 mm per minute, friction surface (galvanized sheet iron, aluminum and flat rubber and pistachio type at two levels (filled splits and closed that was measured and analyzed in completely randomized factorial design. A friction measuring device (built in Ferdowsi University of Mashhad used to measure the friction force. It has a removable table that can move in two directions with adjustable speed. The test sample put into the vessel with internal dimensions of 300 × 150

  4. Nonlinear dynamo mode dynamics in reversed field pinches

    International Nuclear Information System (INIS)

    Fitzpatrick, Richard; Yu, Edmund P.

    2000-01-01

    The nonlinear dynamics of a typical dynamo mode in a reversed field pinch, under the action of the braking torque due to eddy currents excited in a resistive vacuum vessel and the locking torque due to a resonant error-field, is investigated. A simple set of phase evolution equations for the mode is derived: these equations represent an important extension of the well-known equations of Zohm et al. [Europhys. Lett. 11, 745 (1990)] which incorporate a self-consistent calculation of the radial extent of the region of the plasma which corotates with the mode; the width of this region being determined by plasma viscosity. Using these newly developed equations, a comprehensive theory of the influence of a resistive vacuum vessel on error-field locking and unlocking thresholds is developed. Under certain circumstances, a resistive vacuum vessel is found to strongly catalyze locked mode formation. Hopefully, the results obtained in this paper will allow experimentalists to achieve a full understanding of why the so-called ''slinky mode'' locks in some reversed field pinch devices, but not in others. The locking of the slinky mode is currently an issue of outstanding importance in reversed field pinch research. (c) 2000 American Institute of Physics

  5. Nonlinear dynamo mode dynamics in reversed field pinches

    Science.gov (United States)

    Fitzpatrick, Richard; Yu, Edmund P.

    2000-09-01

    The nonlinear dynamics of a typical dynamo mode in a reversed field pinch, under the action of the braking torque due to eddy currents excited in a resistive vacuum vessel and the locking torque due to a resonant error-field, is investigated. A simple set of phase evolution equations for the mode is derived: these equations represent an important extension of the well-known equations of Zohm et al. [Europhys. Lett. 11, 745 (1990)] which incorporate a self-consistent calculation of the radial extent of the region of the plasma which corotates with the mode; the width of this region being determined by plasma viscosity. Using these newly developed equations, a comprehensive theory of the influence of a resistive vacuum vessel on error-field locking and unlocking thresholds is developed. Under certain circumstances, a resistive vacuum vessel is found to strongly catalyze locked mode formation. Hopefully, the results obtained in this paper will allow experimentalists to achieve a full understanding of why the so-called "slinky mode" locks in some reversed field pinch devices, but not in others. The locking of the slinky mode is currently an issue of outstanding importance in reversed field pinch research.

  6. Nonlinear dynamo mode dynamics in reversed field pinches

    Energy Technology Data Exchange (ETDEWEB)

    Fitzpatrick, Richard [Institute for Fusion Studies, Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States); Yu, Edmund P. [Institute for Fusion Studies, Department of Physics, University of Texas at Austin, Austin, Texas 78712 (United States)

    2000-09-01

    The nonlinear dynamics of a typical dynamo mode in a reversed field pinch, under the action of the braking torque due to eddy currents excited in a resistive vacuum vessel and the locking torque due to a resonant error-field, is investigated. A simple set of phase evolution equations for the mode is derived: these equations represent an important extension of the well-known equations of Zohm et al. [Europhys. Lett. 11, 745 (1990)] which incorporate a self-consistent calculation of the radial extent of the region of the plasma which corotates with the mode; the width of this region being determined by plasma viscosity. Using these newly developed equations, a comprehensive theory of the influence of a resistive vacuum vessel on error-field locking and unlocking thresholds is developed. Under certain circumstances, a resistive vacuum vessel is found to strongly catalyze locked mode formation. Hopefully, the results obtained in this paper will allow experimentalists to achieve a full understanding of why the so-called ''slinky mode'' locks in some reversed field pinch devices, but not in others. The locking of the slinky mode is currently an issue of outstanding importance in reversed field pinch research. (c) 2000 American Institute of Physics.

  7. Reducing Visual Discomfort with HMDs Using Dynamic Depth of Field.

    Science.gov (United States)

    Carnegie, Kieran; Rhee, Taehyun

    2015-01-01

    Although head-mounted displays (HMDs) are ideal devices for personal viewing of immersive stereoscopic content, exposure to VR applications on them results in significant discomfort for the majority of people, with symptoms including eye fatigue, headaches, nausea, and sweating. A conflict between accommodation and vergence depth cues on stereoscopic displays is a significant cause of visual discomfort. This article describes the results of an evaluation used to judge the effectiveness of dynamic depth-of-field (DoF) blur in an effort to reduce discomfort caused by exposure to stereoscopic content on HMDs. Using a commercial game engine implementation, study participants report a reduction of visual discomfort on a simulator sickness questionnaire when DoF blurring is enabled. The study participants reported a decrease in symptom severity caused by HMD exposure, indicating that dynamic DoF can effectively reduce visual discomfort.

  8. Hysteresis and parent-metabolite analyses unravel characteristic pesticide transport mechanisms in a mixed land use catchment

    OpenAIRE

    Tang, Ting; Stamm, Christian; van Griensven, Ann; Seuntjens, Piet; Bronders, Jan

    2017-01-01

    Abstract: To properly estimate and manage pesticide occurrence in urban rivers, it is essential, but often highly challenging, to identify the key pesticide transport pathways in association to the main sources. This study examined the concentration-discharge hysteresis behaviour (hysteresis analysis) for three pesticides and the parent-metabolite concentration dynamics for two metabolites at sites with different levels of urban influence in a mixed land use catchment (25 km(2)) within the Sw...

  9. Surface impedance tensor in amorphous wires with helical anisotropy: Magnetic hysteresis and asymmetry

    International Nuclear Information System (INIS)

    Makhnovskiy, D. P.; Panina, L. V.; Mapps, D. J.

    2001-01-01

    This article concerns the investigation of the magnetic behavior of the surface impedance tensor cflx var-sigma in CoSiB amorphous wires having a residual torsion stress and a helical anisotropy. The full tensor cflx var-sigma involving three different components is found by measuring the S 21 parameter at a required excitation with a Hewlett-Packard network/spectrum analyzer at MHz frequencies. In general, the impedance plots versus axial magnetic field H ex exhibit a hysteresis related to that for the case of static magnetization. The diagonal components of cflx var-sigma (longitudinal var-sigma zz and circular var-sigma v ar-phi v ar-phi) show a sharp peak in a narrow field interval where the domain walls form and contribute to the ac magnetization dynamics. This peak is not seen for the off-diagonal component var-sigma zv ar-phi (var-sigma v ar-phi z ) since the existence of the domain structure suppresses it. Applying a dc bias current results in a gradual transition to a nonhysteretic asymmetrical behavior with an enhanced sensitivity. The portions of the experimental plots associated with the rotational dynamic process are in qualitative agreement with the theory based on a single-domain model. [copyright] 2001 American Institute of Physics

  10. Electron dynamics and transport in a mirror field

    International Nuclear Information System (INIS)

    Irie, Haruyuki; Hatori, Tadatsugu.

    1985-01-01

    The nonlinear dynamics and the radial transport of an electron in a magnetic mirror field are considered in the presence of an electrostatic monochromatic wave. It is found that a stochastic heating and a stochastic radial diffusion of electrons can simultaneously occur due to the nonlinear interaction between two motions, one is the bounce motion in the mirror and the other is the motion by the monochromatic wave. Three types of dependence of the diffusion coefficient on the wave amplitude are obtained which are different from that derived by the quasilinear theory. (author)

  11. Dynamic scattering theory for dark-field electron holography of 3D strain fields

    International Nuclear Information System (INIS)

    Lubk, Axel; Javon, Elsa; Cherkashin, Nikolay; Reboh, Shay; Gatel, Christophe; Hÿtch, Martin

    2014-01-01

    Dark-field electron holography maps strain in crystal lattices into reconstructed phases over large fields of view. Here we investigate the details of the lattice strain–reconstructed phase relationship by applying dynamic scattering theory both analytically and numerically. We develop efficient analytic linear projection rules for 3D strain fields, facilitating a straight-forward calculation of reconstructed phases from 3D strained materials. They are used in the following to quantify the influence of various experimental parameters like strain magnitude, specimen thickness, excitation error and surface relaxation. - Author-Highlights: • We derive a simple dynamic scattering formalism for dark field electron holography based on a perturbative two-beam theory. • The formalism facilitates the projection of 3D strain fields by a simple weighting integral. • The weighted projection depends analytically on the diffraction order, the excitation error and the specimen thickness. • The weighting integral formalism represents an important prerequisite towards the development of tomographic strain reconstruction techniques

  12. Compton scattering at finite temperature: thermal field dynamics approach

    International Nuclear Information System (INIS)

    Juraev, F.I.

    2006-01-01

    Full text: Compton scattering is a classical problem of quantum electrodynamics and has been studied in its early beginnings. Perturbation theory and Feynman diagram technique enables comprehensive analysis of this problem on the basis of which famous Klein-Nishina formula is obtained [1, 2]. In this work this problem is extended to the case of finite temperature. Finite-temperature effects in Compton scattering is of practical importance for various processes in relativistic thermal plasmas in astrophysics. Recently Compton effect have been explored using closed-time path formalism with temperature corrections estimated [3]. It was found that the thermal cross section can be larger than that for zero-temperature by several orders of magnitude for the high temperature realistic in astrophysics [3]. In our work we use a main tool to account finite-temperature effects, a real-time finite-temperature quantum field theory, so-called thermofield dynamics [4, 5]. Thermofield dynamics is a canonical formalism to explore field-theoretical processes at finite temperature. It consists of two steps, doubling of Fock space and Bogolyubov transformations. Doubling leads to appearing additional degrees of freedom, called tilded operators which together with usual field operators create so-called thermal doublet. Bogolyubov transformations make field operators temperature-dependent. Using this formalism we treat Compton scattering at finite temperature via replacing in transition amplitude zero-temperature propagators by finite-temperature ones. As a result finite-temperature extension of the Klein-Nishina formula is obtained in which differential cross section is represented as a sum of zero-temperature cross section and finite-temperature correction. The obtained result could be useful in quantum electrodynamics of lasers and for relativistic thermal plasma processes in astrophysics where correct account of finite-temperature effects is important. (author)

  13. Multiferroic hysteresis in MnWO{sub 4}

    Energy Technology Data Exchange (ETDEWEB)

    Finger, Thomas; Komarek, Alexander; Senff, Daniel; Braden, Markus [II. Physikalisches Institut, Universitaet zu Koeln (Germany); Becker-Bohaty, Petra; Bohaty, Ladislav [Institut fuer Kristallographie, Universitaet zu Koeln (Germany); Regnault, Louis-Pierre [CNG-Grenoble / ILL, Grenoble (France); Schmalzl, Karin; Schmidt, Wolfgang [JCNS / ILL, Grenoble (France)

    2009-07-01

    Multiferroic materials or compounds with a strong magnetoelectric effect posses a large application potential in data storage techniques: one would like to replace the common magnetic writing by an electric process, as the generation of the magnetic fields is energy expensive. Quite recently, systems with a peculiar spiral magnetic order were shown to directly induce a spontaneous electric polarization and to exhibit giant magnetoelectric and magnetocapacitance effects, among them MnWO{sub 4}, which crystallizes in a monoclinic structure and undergoes several magnetic phase transitions as a function of temperature. From these phases only the incommensurate non-collinear ordering in the AF2-phase induces an electric polarization and large magnetoelectric effects, fully consistent with recent theories. We have succeeded for the first time to observe a chirality hysteresis curve driven by the electric field. These data can give important information about the pinning of the multiferroic order, which is relevant in view of future applications. We present our temperature dependent studies on the multiferroic hysteresis as well as a characterization of the second harmonics of the spiral.

  14. Numerical and experimental comparison of electromechanical properties and efficiency of HTS and ferromagnetic hysteresis motors

    International Nuclear Information System (INIS)

    Inacio, D; Inacio, S; Pina, J; Goncalves, A; Neves, M Ventim; Rodrigues, A Leao

    2008-01-01

    Hysteresis motors are very attractive in a wide range of fractional power applications, due to its torque-speed characteristics and simplicity of construction. This motor's performance is expected to improve when HTS rotors are used, and in fact, hysteresis motors have shown to be probably the most viable electrical machines using HTS materials. While these motors, either conventional or HTS, are both hysteresis motors, they base their operation on different physical phenomena: hysteretic behaviour in conventional ferromagnetic materials is due to the material's non-linear magnetic properties, while in HTS materials the hysteresis has an ohmic nature and is related with vortices' dynamics. In this paper, theoretical aspects of both conventional and HTS hysteresis motors are discussed, its operation principles are highlighted, and the characteristics of both motors are presented. The characteristics, obtained both by experimental tests and numerical simulation (made with commercial software), are compared, in order to evaluate not only the motor's electromechanical performances but also the overall systems efficiency, including cryogenics for the HTS device

  15. Theoretical Insights on Contraction-Type Iterative Learning Control for Biorobotic Systems with Preisach Hysteresis

    Directory of Open Access Journals (Sweden)

    Tianjiang Hu

    2016-06-01

    Full Text Available This article offers new insights on the learning control approach developed by [Hu et al. IEEE/ASME Trans. Mechatronics, 19(1: 191–200, 2014]. Theoretical insights are further proposed to unveil why the contraction-type iterative learning control (ILC schemes are suitable and effective in compensating for hysteresis, widely existing in biorobotic locomotion. Under such circumstances, iteration-based second-order dynamics is adopted to describe the biorobotic systems acted upon by one unknown Preisach hysteresis term. The memory clearing operator is mathematically proven to enable feasibility of contraction-type ILC methods, regardless of whether the initial state is accurately set or not. The simulation examples confirm that the developed iteration-based controller combined with a preceded operator effectively reduce tracking errors caused by the hysteresis nonlinearity. Furthermore, the new insights on theoretical feasibility are definitively corroborated in accordance with the previously published experimental results.

  16. A model for the hysteresis observed in gating of lysenin channels.

    Science.gov (United States)

    Krueger, Eric; Al Faouri, Radwan; Fologea, Daniel; Henry, Ralph; Straub, David; Salamo, Greg

    2013-12-31

    The pore-forming toxin lysenin self-inserts to form conductance channels in natural and artificial lipid membranes containing sphingomyelin. The inserted channels exhibit voltage regulation and hysteresis of the macroscopic current during the application of positive periodic voltage stimuli. We explored the bi-stable behavior of lysenin channels and present a theoretical approach for the mechanism of the hysteresis to explain its static and dynamic components. This investigation develops a model to incorporate the role of charge accumulation on the bilayer lipid membrane in influencing the channel conduction state. Our model is supported by experimental results and also provides insight into the temperature dependence of lysenin channel hysteresis. Through this work we gain perspective into the mechanism of how the response of a channel protein is determined by previous stimuli. © 2013.

  17. Dynamics of Molecular Gyroscopes Created by Strong Optical Fields

    Science.gov (United States)

    Mullin, Amy

    2015-03-01

    We explore the behavior of molecules in ultra-high angular momentum states prepared in an optical centrifuge and detected with transient IR absorption spectroscopy. In the optical centrifuge, the polarizable electron cloud of molecules interacts with the electric field of linearly polarized light that angularly accelerates over the time of the optical pulse. The centrifuge pulse is generated by combining oppositely chirped pulsed of light. Trapped molecules are driven into high angular momentum states that are spatially oriented with the optical field and have energies far above the average at 300 K. High resolution transient IR spectroscopy reveals the dynamics of collisional energy transfer for the super-rotors. Polarization-dependent studies show that the initial angular momentum orientation persists for many collisions, indicating that molecules in an optical centrifuge behave as quantum gyroscopes. Time-dependent population and energy profiles for individual J- states give information about the dynamics of super-rotors. Research support provided by NSF and the University of Maryland.

  18. Dynamic phase transitions and dynamic phase diagrams of the spin-2 Blume-Capel model under an oscillating magnetic field within the effective-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Ertas, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Deviren, Bayram [Department of Physics, Nevsehir University, 50300 Nevsehir (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-03-15

    The dynamic phase transitions are studied in the kinetic spin-2 Blume-Capel model under a time-dependent oscillating magnetic field using the effective-field theory with correlations. The effective-field dynamic equation for the average magnetization is derived by employing the Glauber transition rates and the phases in the system are obtained by solving this dynamic equation. The nature (first- or second-order) of the dynamic phase transition is characterized by investigating the thermal behavior of the dynamic magnetization and the dynamic phase transition temperatures are obtained. The dynamic phase diagrams are constructed in the reduced temperature and magnetic field amplitude plane and are of seven fundamental types. Phase diagrams contain the paramagnetic (P), ferromagnetic-2 (F{sub 2}) and three coexistence or mixed phase regions, namely the F{sub 2}+P, F{sub 1}+P and F{sub 2}+F{sub 1}+P, which strongly depend on the crystal-field interaction (D) parameter. The system also exhibits the dynamic tricritical behavior. - Highlights: Black-Right-Pointing-Pointer Dynamic phase transitions are studied in spin-2 BC model using EFT. Black-Right-Pointing-Pointer Dynamic phase diagrams are constructed in (T/zJ, h/zJ) plane. Black-Right-Pointing-Pointer Seven fundamental types of dynamic phase diagrams are found in the system. Black-Right-Pointing-Pointer System exhibits dynamic tricritical behavior.

  19. Diversity of hysteresis in a fully cooperative coinfection model

    Science.gov (United States)

    Rodríguez, Jorge P.; Liang, Yu-Hao; Huang, Yu-Jhe; Juang, Jonq

    2018-02-01

    We propose a fully cooperative coinfection model in which singly infected individuals are more likely to acquire a second disease than susceptible ones and doubly infected individuals are also assumed to be more contagious than singly infected ones. The dynamics of such a fully cooperative coinfection model is investigated through the well-mixed approach. In particular, discontinuous outbreak transitions from the disease free state or the low prevalence state to the high prevalence state can be separately observed as a disease transmission rate crosses a threshold αo from the below when the epidemic is still in the early stages. Moreover, discontinuous eradications from the high prevalence state to the low prevalence or disease free state are also separately seen as the transmission rate reaches a threshold α e ( constitute three types of hysteresis, where only one type has been identified before. Complete characterization of these three types of hysteresis in terms of parameters measuring the uniformity of the model is both analytically and numerically provided.

  20. Bean grain hysteresis with induced mechanical damage

    Directory of Open Access Journals (Sweden)

    Renata C. Campos

    Full Text Available ABSTRACT This study aimed to evaluate the effect of mechanical damage on the hysteresis of beans with induced mechanical damage under different conditions of temperature and relative humidity. Beans (Phaseolus vulgaris L. harvested manually with 35% water content (w.b. were used. Part of this product was subjected to induced mechanical damage by Stein Breakage Tester and controlled drying (damaged and control sample, for sorption processes. The sorption isotherms of water were analyzed for different temperature conditions: 20, 30, 40 and 50 oC; and relative humidity: 0.3; 0.4; 0.5; 0.7 and 0.9 (decimal. Equilibrium moisture content data were correlated with six mathematical models, and the Modified Oswin model was the one that best fitted to the experimental data. According to the above mentioned isotherms, it was possible to observe the phenomenon of hysteresis of damaged and control samples, and this phenomenon was more pronounced in control ones.

  1. Yanqing solar field: Dynamic optical model and operational safety analysis

    International Nuclear Information System (INIS)

    Zhao, Dongming; Wang, Zhifeng; Xu, Ershu; Zhu, Lingzhi; Lei, Dongqiang; Xu, Li; Yuan, Guofeng

    2017-01-01

    Highlights: • A dynamic optical model of the Yanqing solar field was built. • Tracking angle characteristics were studied with different SCA layouts and time. • The average energy flux was simulated across four clear days. • Influences of defocus angles for energy flux were analyzed. - Abstract: A dynamic optical model was established for the Yanqing solar field at the parabolic trough solar thermal power plant and a simulation was conducted on four separate days of clear weather (March 3rd, June 2nd, September 25th, December 17th). The solar collector assembly (SCA) was comprised of a North-South and East-West layout. The model consisted of the following modules: DNI, SCA operational, and SCA optical. The tracking angle characteristics were analyzed and the results showed that the East-West layout of the tracking system was the most viable. The average energy flux was simulated for a given time period and different SCA layouts, yielding an average flux of 6 kW/m 2 , which was then used as the design and operational standards of the Yanqing parabolic trough plant. The mass flow of North-South layout was relatively stable. The influences of the defocus angles on both the average energy flux and the circumferential flux distribution were also studied. The results provided a theoretical basis for the following components: solar field design, mass flow control of the heat transfer fluid, design and operation of the tracking system, operational safety of SCAs, and power production prediction in the Yanqing 1 MW parabolic trough plant.

  2. Factors influencing hysteresis characteristics of concrete dam deformation

    Directory of Open Access Journals (Sweden)

    Jia-he Zhang

    2017-04-01

    Full Text Available Thermal deformation of a concrete dam changes periodically, and its variation lags behind the air temperature variation. The lag, known as the hysteresis time, is generally attributed to the low velocity of heat conduction in concrete, but this explanation is not entirely sufficient. In this paper, analytical solutions of displacement hysteresis time for a cantilever beam and an arch ring are derived. The influence of different factors on the displacement hysteresis time was examined. A finite element model was used to verify the reliability of the theoretical analytical solutions. The following conclusions are reached: (1 the hysteresis time of the mean temperature is longer than that of the linearly distributed temperature difference; (2 the dam type has a large impact on the displacement hysteresis time, and the hysteresis time of the horizontal displacement of an arch dam is longer than that of a gravity dam; (3 the reservoir water temperature variation lags behind of the air temperature variation, which intensifies the differences in the horizontal displacement hysteresis time between the gravity dam and the arch dam; (4 with a decrease in elevation, the horizontal displacement hysteresis time of a gravity dam tends to increase, whereas the horizontal displacement hysteresis time of an arch dam is likely to increase initially, and then decrease; and (5 along the width of the dam, the horizontal displacement hysteresis time of a gravity dam decreases as a whole, while the horizontal displacement hysteresis time of an arch dam is shorter near the center and longer near dam surfaces.

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

    Science.gov (United States)

    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.”

  4. Hysteresis and compensation behaviors of mixed spin-2 and spin-1 hexagonal Ising nanowire core–shell structure

    International Nuclear Information System (INIS)

    Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.; Bahmad, L.

    2015-01-01

    The magnetic behaviors of a mixed spins (2-1) hexagonal Ising nanowire with core–shell structure are investigated by using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperatures of core–shell are studied for different values of crystal field and exchange interactions. The thermal and magnetic hysteresis cycles are given for different values of the crystal field. - Highlights: • Critical temperature increase when exchange interaction increasing in core-shell. • Hysteresis loop areas decrease at above transition temperature. • Magnetic coercive field decrease when crystal field increasing. • Magnetic coercive field increase when exchange interaction increasing

  5. Transport hysteresis and hydrogen isotope effect on confinement

    Science.gov (United States)

    Itoh, S.-I.; Itoh, K.

    2018-03-01

    A Gedankenexperiment on hydrogen isotope effect is developed, using the transport model with transport hysteresis. The transport model with hysteresis is applied to case where the modulational electron cyclotron heating is imposed near the mid-radius of the toroidal plasmas. The perturbation propagates either outward or inward, being associated with the clockwise (CW) hysteresis or counter-clockwise (CCW) hysteresis, respectively. The hydrogen isotope effects on the CW and CCW hysteresis are investigated. The local component of turbulence-driven transport is assumed to be the gyro-Bohm diffusion. While the effect of hydrogen mass number is screened in the response of CW hysteresis, it is amplified in CCW hysteresis. This result motivates the experimental studies to compare CW and CCW cases in order to obtain further insight into the physics of hydrogen isotope effects.

  6. Modelling of dielectric hysteresis loops in ferroelectric semiconductors with charged defects

    International Nuclear Information System (INIS)

    Morozovska, Anna N; Eliseev, Eugene A

    2004-01-01

    We have proposed the phenomenological description of dielectric hysteresis loops in ferroelectric semiconductors with charged defects and prevailing extrinsic conductivity. We have modified the Landau-Ginsburg approach and shown that the macroscopic state of the aforementioned inhomogeneous system can be described by three coupled equations for three order parameters. Both the experimentally observed coercive field values well below the thermodynamic values and the various hysteresis-loop deformations (constricted and double loops) have been obtained in the framework of our model. The obtained results quantitatively explain the ferroelectric switching in such ferroelectric materials as thick PZT films

  7. Influence of tensile stress and frequency on the longitudinal magnetic hysteresis of amorphous wires

    International Nuclear Information System (INIS)

    Torres, Carlos; Maria Munoz, Jose; Hernandez-Gomez, Pablo; Francisco, Carlos de

    2010-01-01

    This work studies the longitudinal magnetic hysteresis of amorphous wires with different Fe or Co compositions through an external magnetic field in the axial direction. Measurements have been carried out with the help of a digitally processed system in the 50 Hz-1 kHz frequency range. In addition, the influence of different tensile stresses has been also analyzed. The results show that both parameters change considerably the magnetic hysteresis of the wires but in a different way depending on their composition. This behaviour has been interpreted in terms of the different domain distribution associated with the opposite sign of the magnetostriction for Fe and Co-based wires, respectively.

  8. Magnetic-field-induced suppression of the amorphous blue phase.

    Science.gov (United States)

    Challa, P K; Sprunt, S N; Jákli, A; Gleeson, J T

    2014-01-01

    We present magneto-optical measurements on two liquid crystals that exhibit a wide temperature-range amorphous blue phase (BPIII). Magnetic fields up to 25 T are found to suppress the onset of BPIII in both materials by almost 1 °C. This effect appears to increase nonlinearly with the field strength. The effect of high fields on established BPIIIs is also reported, in which we find significant hysteresis and very slow dynamics. Possible explanations of these results are discussed.

  9. Direct Hysteresis Heating of Catalytically Active Ni–Co Nanoparticles as Steam Reforming Catalyst

    DEFF Research Database (Denmark)

    Mortensen, Peter Mølgaard; Engbæk, Jakob Soland; Vendelbo, Søren Bastholm

    2017-01-01

    We demonstrated a proof-of-concept catalytic steam reforming flow reactor system heated only by supported magnetic nickel–cobalt nanoparticles in an oscillating magnetic field. The heat transfer was facilitated by the hysteresis heating in the nickel–cobalt nanoparticles alone. This produced...... a sufficient power input to equilibrate the reaction at above 780 °C with more than 98% conversion of methane. The high conversion of methane indicated that Co-rich nanoparticles with a high Curie temperature provide sufficient heat to enable the endothermic reaction, with the catalytic activity facilitated...... by the Ni content in the nanoparticles. The magnetic hysteresis losses obtained from temperature-dependent hysteresis measurements were found to correlate well with the heat generation in the system. The direct heating of the catalytic system provides a fast heat transfer and thereby overcomes the heat...

  10. Microscopic Charge Transport and Recombination Processes behind the Photoelectric Hysteresis in Perovskite Solar Cells.

    Science.gov (United States)

    Shi, Jiangjian; Zhang, Huiyin; Xu, Xin; Li, Dongmei; Luo, Yanhong; Meng, Qingbo

    2016-10-01

    The microscopic charge transport and recombination processes behind the widely concerned photoelectric hysteresis in the perovskite solar cell have been investigated with both in situ transient photovoltage/photocurrent measurements and the semiconductor device simulation. Time-dependent behaviors of intensity and direction of the photocurrent and photovoltage are observed under the steady-state bias voltages and open-circuit conditions. These charge processes reveal the electric properties of the cell, demonstrating evolutions of both strength and direction of the internal electric field during the hysteresis. Further calculation indicates that this behavior is mainly attributed to both the interfacial doping and defect effects induced by the ion accumulation, which may be the origins for the general hysteresis in this cell. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Hysteresis compensation technique applied to polymer optical fiber curvature sensor for lower limb exoskeletons

    Science.gov (United States)

    Gomes Leal-Junior, Arnaldo; Frizera-Neto, Anselmo; José Pontes, Maria; Rodrigues Botelho, Thomaz

    2017-12-01

    Polymer optical fiber (POF) curvature sensors present some advantages over conventional techniques for angle measurements, such as their light weight, compactness and immunity to electromagnetic fields. However, high hysteresis can occur in POF curvature sensors due to the polymer viscoelastic response. In order to overcome this limitation, this paper shows how the hysteresis sensor can be compensated by a calibration equation relating the measured output signal to the sensor’s angular velocity. The proposed method is validated using an exoskeleton with an active joint on the knee for flexion and extension rehabilitation exercises. The results show a decrease in sensor hysteresis and a decrease by more than two times in the error between the POF sensor and the potentiometer, which is employed for the angle measurement of the exoskeleton knee joint.

  12. Effects of the amorphization on hysteresis loops of the amorphous spin-1/2 Ising system

    International Nuclear Information System (INIS)

    Essaoudi, I.; Ainane, A.; Saber, M.; Miguel, J.J. de

    2009-01-01

    We examine the effects of the amorphization on the hysteresis loops of the amorphous spin-1/2 Ising system using the effective field theory within a probability distribution technique that accounts for the self-spin correlation functions. The magnetization, the transverse and longitudinal susceptibilities, and pyromagnetic coefficient are also studied in detail

  13. Control of Linear Systems with Preisach Hysteresis Output with Application to Damage Reduction

    DEFF Research Database (Denmark)

    Barradas Berglind, Jose de Jesus; Wisniewski, Rafal

    2015-01-01

    The focus of this work is on the Preisach hysteresis operator which has been widely used in fields such as ferromagnetics, phase transitions, filtration through porous media, and shape memory alloys. The main purpose is to incorporate discrete linear time invariant systems with discretized Preisach...... turbine model. The results are evaluated for three different cases and the impact in the control effort is analyzed....

  14. The dynamics of coupled atom and field assisted by continuous external pumping

    Energy Technology Data Exchange (ETDEWEB)

    Burlak, G.; Hernandez, J.A. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma de Morelos, Cuernavaca, Morelos (Mexico); Starostenko, O. [Departamento de Fisica, Electronica, Sistemas y Mecatronica, Universidad de las Americas, 72820 Puebla (Mexico)

    2006-07-01

    The dynamics of a coupled system comprising a two-level atom and cavity field assisted by a continuous external classical field (driving Jaynes-Cummings model) is studied. When the initial field is prepared in a coherent state, the dynamics strongly depends on the algebraic sum of both fields. If this sum is zero (the compensative case) in the system, only the vacuum Rabi oscillations occur. The results with dissipation and external field detuning from the cavity field are also discussed. (Author)

  15. The dynamics of coupled atom and field assisted by continuous external pumping

    International Nuclear Information System (INIS)

    Burlak, G.; Hernandez, J.A.; Starostenko, O.

    2006-01-01

    The dynamics of a coupled system comprising a two-level atom and cavity field assisted by a continuous external classical field (driving Jaynes-Cummings model) is studied. When the initial field is prepared in a coherent state, the dynamics strongly depends on the algebraic sum of both fields. If this sum is zero (the compensative case) in the system, only the vacuum Rabi oscillations occur. The results with dissipation and external field detuning from the cavity field are also discussed. (Author)

  16. Annular billiard dynamics in a circularly polarized strong laser field

    Science.gov (United States)

    Kamor, A.; Mauger, F.; Chandre, C.; Uzer, T.

    2012-01-01

    We analyze the dynamics of a valence electron of the buckminsterfullerene molecule (C60) subjected to a circularly polarized laser field by modeling it with the motion of a classical particle in an annular billiard. We show that the phase space of the billiard model gives rise to three distinct trajectories: “whispering gallery orbits,” which hit only the outer billiard wall; “daisy orbits,” which hit both billiard walls (while rotating solely clockwise or counterclockwise for all time); and orbits that only visit the downfield part of the billiard, as measured relative to the laser term. These trajectories, in general, maintain their distinct features, even as the intensity is increased from 1010 to 1014Wcm-2. We attribute this robust separation of phase space to the existence of twistless tori.

  17. Mean-field games with logistic population dynamics

    KAUST Repository

    Gomes, Diogo A.

    2013-12-01

    In its standard form, a mean-field game can be defined by coupled system of equations, a Hamilton-Jacobi equation for the value function of agents and a Fokker-Planck equation for the density of agents. Traditionally, the latter equation is adjoint to the linearization of the former. Since the Fokker-Planck equation models a population dynamic, we introduce natural features such as seeding and birth, and nonlinear death rates. In this paper we analyze a stationary meanfield game in one dimension, illustrating various techniques to obtain regularity of solutions in this class of systems. In particular we consider a logistic-type model for birth and death of the agents which is natural in problems where crowding affects the death rate of the agents. The introduction of these new terms requires a number of new ideas to obtain wellposedness. In a forthcoming publication we will address higher dimensional models. ©2013 IEEE.

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

    International Nuclear Information System (INIS)

    Wang, Dan; Wang, Linxiang; Melnik, Roderick

    2016-01-01

    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. - Highlights: • Predict the polycrystalline hysteresis effectively. • Sub hysteresis loop can be captured. • Frequency dependence is naturally included.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Dan [State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, 310027 Hangzhou (China); Wang, Linxiang, E-mail: wanglx236@zju.edu.cn [State Key Laboratory of Fluid Power and Mechatronic Systems, Zhejiang University, 310027 Hangzhou (China); Melnik, Roderick [MS2Discovery Interdisciplinary Research Institute, Wilfrid Laurier University, Waterloo, ON, Canada N2L 3L5 (Canada)

    2016-07-15

    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. - Highlights: • Predict the polycrystalline hysteresis effectively. • Sub hysteresis loop can be captured. • Frequency dependence is naturally included.

  20. Field theoretic approach to dynamical orbital localization in ab initio molecular dynamics

    International Nuclear Information System (INIS)

    Thomas, Jordan W.; Iftimie, Radu; Tuckerman, Mark E.

    2004-01-01

    Techniques from gauge-field theory are employed to derive an alternative formulation of the Car-Parrinello ab initio molecular-dynamics method that allows maximally localized Wannier orbitals to be generated dynamically as the calculation proceeds. In particular, the Car-Parrinello Lagrangian is mapped onto an SU(n) non-Abelian gauge-field theory and the fictitious kinetic energy in the Car-Parrinello Lagrangian is modified to yield a fully gauge-invariant form. The Dirac gauge-fixing method is then employed to derive a set of equations of motion that automatically maintain orbital locality by restricting the orbitals to remain in the 'Wannier gauge'. An approximate algorithm for integrating the equations of motion that is stable and maintains orbital locality is then developed based on the exact equations of motion. It is shown in a realistic application (64 water molecules plus one hydrogen-chloride molecule in a periodic box) that orbital locality can be maintained with only a modest increase in CPU time. The ability to keep orbitals localized in an ab initio molecular-dynamics calculation is a crucial ingredient in the development of emerging linear scaling approaches

  1. Behavioral dynamics and neural grounding of a dynamic field theory of multi-object tracking.

    Science.gov (United States)

    Spencer, J P; Barich, K; Goldberg, J; Perone, S

    2012-09-01

    The ability to dynamically track moving objects in the environment is crucial for efficient interaction with the local surrounds. Here, we examined this ability in the context of the multi-object tracking (MOT) task. Several theories have been proposed to explain how people track moving objects; however, only one of these previous theories is implemented in a real-time process model, and there has been no direct contact between theories of object tracking and the growing neural literature using ERPs and fMRI. Here, we present a neural process model of object tracking that builds from a Dynamic Field Theory of spatial cognition. Simulations reveal that our dynamic field model captures recent behavioral data examining the impact of speed and tracking duration on MOT performance. Moreover, we show that the same model with the same trajectories and parameters can shed light on recent ERP results probing how people distribute attentional resources to targets vs. distractors. We conclude by comparing this new theory of object tracking to other recent accounts, and discuss how the neural grounding of the theory might be effectively explored in future work.

  2. Radiation-like scalar field and gauge fields in cosmology for a theory with dynamical time

    Science.gov (United States)

    Benisty, David; Guendelman, E. I.

    2016-09-01

    Cosmological solutions with a scalar field behaving as radiation are obtained, in the context of gravitational theory with dynamical time. The solution requires the spacial curvature of the universe k, to be zero, unlike the standard radiation solutions, which do not impose any constraint on the spatial curvature of the universe. This is because only such k = 0 radiation solutions pose a homothetic Killing vector. This kind of theory can be used to generalize electromagnetism and other gauge theories, in curved spacetime, and there are no deviations from standard gauge field equation (like Maxwell equations) in the case there exist a conformal Killing vector. But there could be departures from Maxwell and Yang-Mills equations, for more general spacetimes.

  3. Geosynchronous magnetic field responses to fast solar wind dynamic pressure enhancements: MHD field model

    Directory of Open Access Journals (Sweden)

    T. R. Sun

    2012-08-01

    Full Text Available We performed global MHD simulations of the geosynchronous magnetic field in response to fast solar wind dynamic pressure (Pd enhancements. Taking three Pd enhancement events in 2000 as examples, we found that the main features of the total field B and the dominant component Bz can be efficiently predicted by the MHD model. The predicted B and Bz varies with local time, with the highest level near noon and a slightly lower level around mid-night. However, it is more challenging to accurately predict the responses of the smaller component at the geosynchronous orbit (i.e., Bx and By. In contrast, the limitations of T01 model in predicting responses to fast Pd enhancements are presented.

  4. Quantum mean-field theory of collective dynamics and tunneling

    Energy Technology Data Exchange (ETDEWEB)

    Negele, J.W.

    1981-01-01

    A fundamental problem in quantum many-body theory is formulation of a microscopic theory of collective motion. For self-bound, saturating systems like finite nuclei described in the context of nonrelativistic quantum mechanics with static interactions, the essential problem is how to formulate a systematic quantal theory in which the relevant collective variables and their dynamics arise directly and naturally from the Hamiltonian and the system under consideration. Significant progress has been made recently in formulating the quantum many-body problem in terms of an expansion about solutions to time-dependent mean-field equations. The essential ideas, principal results, and illustrative examples are summarized. An exact expression for an observable of interest is written using a functional integral representation for the evolution operator, and tractable time-dependent mean field equations are obtained by application of the stationary-phase approximation (SPA) to the functional integral. Corrections to the lowest-order theory may be systematically enumerated. 6 figures. (RWR)

  5. Non-local correlations within dynamical mean field theory

    Energy Technology Data Exchange (ETDEWEB)

    Li, Gang

    2009-03-15

    The contributions from the non-local fluctuations to the dynamical mean field theory (DMFT) were studied using the recently proposed dual fermion approach. Straight forward cluster extensions of DMFT need the solution of a small cluster, where all the short-range correlations are fully taken into account. All the correlations beyond the cluster scope are treated in the mean-field level. In the dual fermion method, only a single impurity problem needs to be solved. Both the short and long-range correlations could be considered on equal footing in this method. The weak-coupling nature of the dual fermion ensures the validity of the finite order diagram expansion. The one and two particle Green's functions calculated from the dual fermion approach agree well with the Quantum Monte Carlo solutions, and the computation time is considerably less than with the latter method. The access of the long-range order allows us to investigate the collective behavior of the electron system, e.g. spin wave excitations. (orig.)

  6. Non-local correlations within dynamical mean field theory

    International Nuclear Information System (INIS)

    Li, Gang

    2009-03-01

    The contributions from the non-local fluctuations to the dynamical mean field theory (DMFT) were studied using the recently proposed dual fermion approach. Straight forward cluster extensions of DMFT need the solution of a small cluster, where all the short-range correlations are fully taken into account. All the correlations beyond the cluster scope are treated in the mean-field level. In the dual fermion method, only a single impurity problem needs to be solved. Both the short and long-range correlations could be considered on equal footing in this method. The weak-coupling nature of the dual fermion ensures the validity of the finite order diagram expansion. The one and two particle Green's functions calculated from the dual fermion approach agree well with the Quantum Monte Carlo solutions, and the computation time is considerably less than with the latter method. The access of the long-range order allows us to investigate the collective behavior of the electron system, e.g. spin wave excitations. (orig.)

  7. MOBILE TECHNOLOGY AIDED FIELD SALES PROCESS MANAGEMENT WIYH DYNAMICS ANYWHERE FOR MICROSOFT DYNAMIC NAV

    Directory of Open Access Journals (Sweden)

    Simon Sándor

    2013-03-01

    Full Text Available The evolution of information society, globalisation, made great changes concerning the human-computer relationship. Mobile technology gives new perspectives for the administration of enterprises and decision making. Microsoft Dynamics NAV is not only a software capable to model the various activities of a firm through the desktop platform, but with a properly developed user interface which is optimised for a mobile device, the possibilities of the use of this ERP software can be broadened with workflows characterised with great distances. In this study I show how a field sales workflow can be modelled and managed by me with the software environment “NAV Anywhere Framework”. The survey gives a closer look at both a suggestible administrative process for an imagined workflow and its technical management on a mobile device. For my development creates specialised and dynamic web pages for a mobile device, it can be accessible from a lot of types of smart phones and tablet computers.

  8. Characterization of hysteresis in magnetic systems: A Preisach approach

    Science.gov (United States)

    Mitchler, Patricia Darlene

    The phenomenon of hysteresis is perhaps the most widely recognized microscopic manifestation of magnetic ordering, and is the principal feature which is responsible for technologically-oriented applications of magnetic materials such as permanent magnets and recording media. Interest in a phenomenological model of hysteresis originally proposed by Preisach in 1935 has been renewed recently, particularly in engineering applications, such as the characterization of magnetic recording media and magnetostrictive materials. Thus, a rigorous assessment of the capabilities and limitations of the Preisach model for characterizing magnetic materials is of considerable importance from both fundamental and technological perspectives. The fundamental characteristics of hysteresis are discussed and a theoretical background for the processes involved in magnetic systems is established. A generalized version of the scalar Preisach model, which includes original contributions, is developed to extend the model's abilities to describe the effects of the structure of the initially demagnetized state, the presence and nature of interactions, the system's coercive field distribution, and especially, the effects of temperature and experimental wart time, on the observed hysteretic properties of a variety of magnetic systems including spin glasses, ferromagnets, ferrimagnets, and superparamagnets. The moment and remanence of magnetic systems are measured as a function of applied field and temperature, using both a vibrating sample magnetometer (VSM) and a SQUID-based magnetometer. A Preisach analysis of the data is used to characterize the irreversible response of six magnetic systems: CrO 2 audio tape; magnetoferritin; a Nd2Fe14B permanent magnet; a floppy disk medium; and longitudinal and perpendicular cobalt-chromium-based hard disk materials. The ambiguous nature of tools presently used to analyze the nature of magnetic systems, such as the application of Henkel plots to the analysis

  9. Dynamic magnetic behavior of the mixed-spin bilayer system in an oscillating field within the mean-field theory

    International Nuclear Information System (INIS)

    Ertaş, Mehmet; Keskin, Mustafa

    2012-01-01

    The dynamic magnetic behavior of the mixed Ising bilayer system (σ=2 and S=5/2), with a crystal-field interaction in an oscillating field are studied, within the mean-field approach, by using the Glauber-type stochastic dynamics for both ferromagnetic/ferromagnetic and antiferromagnetic/ferromagnetic interactions. The time variations of average magnetizations and the temperature dependence of the dynamic magnetizations are investigated. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior depending on interaction parameters. -- Highlights: ► Dynamic magnetic behavior of the mixed Ising bilayer system is investigated within the Glauber-type stochastic dynamics. ► The time variations of average magnetizations are studied to find the phases. ► The temperature dependence of the dynamic magnetizations is investigated to obtain the dynamic phase transition points. ► The dynamic phase diagrams are presented and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior.

  10. Dynamic magnetic behavior of the mixed-spin bilayer system in an oscillating field within the mean-field theory

    Energy Technology Data Exchange (ETDEWEB)

    Ertaş, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2012-07-23

    The dynamic magnetic behavior of the mixed Ising bilayer system (σ=2 and S=5/2), with a crystal-field interaction in an oscillating field are studied, within the mean-field approach, by using the Glauber-type stochastic dynamics for both ferromagnetic/ferromagnetic and antiferromagnetic/ferromagnetic interactions. The time variations of average magnetizations and the temperature dependence of the dynamic magnetizations are investigated. The dynamic phase diagrams are presented in the reduced temperature and magnetic field amplitude plane and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior depending on interaction parameters. -- Highlights: ► Dynamic magnetic behavior of the mixed Ising bilayer system is investigated within the Glauber-type stochastic dynamics. ► The time variations of average magnetizations are studied to find the phases. ► The temperature dependence of the dynamic magnetizations is investigated to obtain the dynamic phase transition points. ► The dynamic phase diagrams are presented and they exhibit several ordered phases, coexistence phase regions and critical points as well as a re-entrant behavior.

  11. Atomistic modeling of metal surfaces under electric fields: direct coupling of electric fields to a molecular dynamics algorithm

    CERN Document Server

    Djurabekova, Flyura; Pohjonen, Aarne; Nordlund, Kai

    2011-01-01

    The effect of electric fields on metal surfaces is fairly well studied, resulting in numerous analytical models developed to understand the mechanisms of ionization of surface atoms observed at very high electric fields, as well as the general behavior of a metal surface in this condition. However, the derivation of analytical models does not include explicitly the structural properties of metals, missing the link between the instantaneous effects owing to the applied field and the consequent response observed in the metal surface as a result of an extended application of an electric field. In the present work, we have developed a concurrent electrodynamic–molecular dynamic model for the dynamical simulation of an electric-field effect and subsequent modification of a metal surface in the framework of an atomistic molecular dynamics (MD) approach. The partial charge induced on the surface atoms by the electric field is assessed by applying the classical Gauss law. The electric forces acting on the partially...

  12. Method and apparatus for sub-hysteresis discrimination

    Science.gov (United States)

    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.

  13. Asymmetrically shaped hysteresis loop in exchange-biased FeNi/FeMn film

    International Nuclear Information System (INIS)

    Gnatchenko, S.L.; Merenkov, D.N.; Bludov, A.N.; Pishko, V.V.; Shakhayeva, Yu.A.; Baran, M.; Szymczak, R.; Novosad, V.A.

    2006-01-01

    The magnetization reversal of the bilayer polycrystalline FeNi(50 A)/FeMn(50 A) film sputtered in a magnetic field has been studied by magnetic and magneto-optical techniques. The external magnetic fields were applied along the easy or hard magnetization axis of the ferromagnetic permalloy layer. The asymmetry of hysteresis loop has been found. Appreciable asymmetry and the exchange bias were observed only in the field applied along the easy axis. The specific features of magnetization reversal were explained within the phenomenological model that involves high-order exchange anisotropy and misalignment of the easy axes of the antiferromagnetic and ferromagnetic layers. It has been shown that the film can exist in one of three equilibrium magnetic states in the field applied along the easy axis. The transitions between these states occur as first-order phase transitions. The observed hysteresis loop asymmetry is related to the existence of the metastable state

  14. The Dynamics of Oblate Drop Between Heterogeneous Plates Under Alternating Electric Field. Non-uniform Field

    Science.gov (United States)

    Kashina, M. A.; Alabuzhev, A. A.

    2018-02-01

    The dynamics of the incompressible fluid drop under the non-uniform electric field are considered. The drop is bounded axially by two parallel solid planes and the case of heterogeneous plates is investigated. The external electric field acts as an external force that causes motion of the contact line. We assume that the electric current is alternative current and the AC filed amplitude is a spatially non-uniform function. In equilibrium, the drop has the form of a circular cylinder. The equilibrium contact angle is 0.5 π. In order to describe this contact line motion the modified Hocking boundary condition is applied: the velocity of the contact line is proportional to the deviation of the contact angle and the speed of the fast relaxation processes, which frequency is proportional to twice the frequency of the electric field. The Hocking parameter depends on the polar angle, i.e. the coefficient of the interaction between the plate and the fluid (the contact line) is a function of the plane coordinates. This function is expanded in a series of the Laplace operator eigenfunctions.

  15. submitter Hysteresis Losses and Effective $J_{c}(B)$ Scaling Law for ITER $Nb_{3}Sn$ Strands

    CERN Document Server

    Seiler, E; Bordini, B; Bottura, L; Bessette, D; Vostner, A; Devred, A

    2016-01-01

    Hysteresis losses of five $Nb_{3}Sn$ International Thermonuclear Experimental Reactor reference strands were investigated by means of magnetization loop measurements in a vibrating sample magnetometer in a perpendicularly applied magnetic field. The magnetization loops were recorded while continuously sweeping the applied field between the extreme values $±B_m$, covering a wide range of maximum applied fields (0.2-10 T). In this paper, we compare the directly determined hysteresis losses based on the area of the smaller measured loops and the losses calculated by the integration of the width ΔM of the $B_m$ = 10 T magnetization loop. A suitable fitting function is proposed to describe the ΔM(B) dependence, which leads, for each strand, to an excellent agreement with the experimentally determined hysteresis losses, magnetization, and pinning force. Transport critical current measurements in a perpendicularly applied magnetic field were also performed for all the strands, and on the basis of the comparison w...

  16. Information money fields of cyclic oscillations in nonlinear dynamic economic system

    OpenAIRE

    Ledenyov, Dimitri O.; Ledenyov, Viktor O.

    2015-01-01

    Article introduces the notion of information money fields of the cyclic oscillations of the economic variables in the nonlinear dynamic economic system for the first time, and presents an original research on the Ledenyov theory on the information money fields of the cyclic oscillations of the economic variables in the nonlinear dynamic economic system. The Ledenyov theory on the information money fields of the cyclic oscillations of economic variables in the nonlinear dynamic economic system...

  17. A Temperature-Dependent Hysteresis Model for Relaxor Ferroelectric Compounds

    National Research Council Canada - National Science Library

    Raye, Julie K; Smith, Ralph C

    2004-01-01

    This paper summarizes the development of a homogenized free energy model which characterizes the temperature-dependent hysteresis and constitutive nonlinearities inherent to relaxor ferroelectric materials...

  18. A Free Energy Model for Hysteresis Ferroelectric Materials

    National Research Council Canada - National Science Library

    Smith, Ralph C; Ounaies, Zoubeida; Seelecke, Stefan; Smith, Joshua

    2003-01-01

    This paper provides a theory for quantifying the hysteresis and constitutive nonlinearities inherent to piezoceramic compounds through a combination of free energy analysis and stochastic homogenization techniques...

  19. Mode dynamics and confinement in the reversed field pinch

    International Nuclear Information System (INIS)

    Brunsell, P.R.; Bergsaker, H.; Brzozowski, J.H.; Cecconello, M.; Drake, J.R.; Malmberg, J.-A.; Scheffel, J.; Schnack, D.D.

    2001-01-01

    Tearing mode dynamics and toroidal plasma flow in the RFP has been experimentally studied in the Extrap T2 device. A toroidally localised, stationary magnetic field perturbation, the 'slinky mode' is formed in nearly all discharges. There is a tendency of increased phase alignment of different toroidal Fourier modes, resulting in higher localised mode amplitudes, with higher magnetic fluctuation level. The fluctuation level increases slightly with increasing plasma current and plasma density. The toroidal plasma flow velocity and the ion temperature has been measured with Doppler spectroscopy. Both the toroidal plasma velocity and the ion temperature clearly increase with I/N. Initial, preliminary experimental results obtained very recently after a complete change of the Extrap T2 front-end system (first wall, shell, TF coil), show that an operational window with mode rotation most likely exists in the rebuilt device, in contrast to the earlier case discussed above. A numerical code DEBSP has been developed to simulate the behaviour of RFP confinement in realistic geometry, including essential transport physics. Resulting scaling laws are presented and compared with results from Extrap T2 and other RFP experiments. (author)

  20. Polarization as a field variable from molecular dynamics simulations

    Science.gov (United States)

    Mandadapu, Kranthi K.; Templeton, Jeremy; Lee, Jonathan

    2012-11-01

    In this talk, we show that polarization density, an important quantity in electromagnetism, can be obtained from molecular dynamics simulations. We show that the Irving and Kirkwood procedure used for obtaining stresses and heat fluxes in terms of the microscopic quantities can be extended to the case of electrostatics where the macroscopic electrostatic equation can be derived starting with the microscopic electrostatic equation, microscopic density of charges and using a phase-space distribution function and a suitable localization function. As a result, we obtain an expression for polarization density as a field variable in terms of the microscopic dipole moments and quadrupole moments and higher order terms depending upon the degree of the polynomial used for the localization function. Finally, we apply this method to obtain the dielectric constant of bulk water and to study the polarization effects in electric double layer calculations. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

  1. Hysteresis Loss Analysis of Soft Magnetic Materials Under Direct Current Bias Conditions (Preprint)

    Science.gov (United States)

    2015-09-01

    activation energies may not contribute to the magnetization process and higher energy walls may be mobilized, which would not be activated otherwise...measured hysteresis losses for the same Metglas core at a fixed Bmax of 0.1 Tesla . The origin of the observed behavior is easily understood by comparing...constant at 0.1 Tesla by changing the value of the applied field for each bias field, are given in Figure 5 for the Metglas material. Comparison of Figures

  2. Dynamic wave field synthesis: enabling the generation of field distributions with a large space-bandwidth product

    OpenAIRE

    Kamau, Edwin Ngugi

    2016-01-01

    The generation and manipulation of electromagnetic field distributions plays an essential role in physics in general, and particularly in the vast field of physical optics. In the current state of the art, one of the most convenient methods of performing this task is provided by either static or dynamic diffractive as well as holographic optical elements. Currently available dynamic optical elements, such as spatial light modulators, do offer on the one hand high temporal flexibility. They ho...

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

    Energy Technology Data Exchange (ETDEWEB)

    Aljanaideh, Omar, E-mail: omaryanni@gmail.com [Department of Mechanical Engineering, The University of Jordan, Amman 11942 (Jordan); Habineza, Didace; Rakotondrabe, Micky [AS2M department, FEMTO-ST Institute, Univ. Bourgogne Franche-Comté, Univ. de Franche-Comté/CNRS/ENSMM, 25000 Besançon (France); Al Janaideh, Mohammad [Department of Mechanical and Industrial Engineering, The Mechatronics and Microsystems Design Laboratory, University of Toronto (Canada); Department of Mechatronics Engineering, The University of Jordan, Amman 11942 (Jordan)

    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.

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

    International Nuclear Information System (INIS)

    Aljanaideh, Omar; Habineza, Didace; Rakotondrabe, Micky; Al Janaideh, Mohammad

    2016-01-01

    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.

  5. Changes in Wetting Hysteresis During Bioremediation: Changes in fluid flow behavior monitored with low-frequency seismic attenuation

    Science.gov (United States)

    Wempe, W.; Spetzler, H.; Kittleson, C.; Pursley, J.

    2003-12-01

    We observed significant reduction in wetting hysteresis with time while a diesel-contaminated quartz crystal was dipped in and out of an oil-reducing bacteria solution. This wetting hysteresis is significantly greater than the wetting hysteresis when the diesel-contaminated quartz crystal is dipped in and out of (1) water, (2) diesel and (3) the bacterial food solution that does not contain bacteria. The reduction in wetting hysteresis of the bacteria solution on the quartz surface results from a reduction in the advancing contact angle formed at the air-liquid-quartz contact with time; the receding contact angle remains the same with time. Our results suggest that the bacteria solution moves across the quartz surface with less resistance after bioremediation has begun. These results imply that bioremediation may influence fluid flow behavior with time. For many fluid-solid systems there is a difference between the contact angle while a contact line advances and recedes across a solid surface; this difference is known as wetting hysteresis. Changes in wetting hysteresis can occur from changes in surface tension or the surface topography. Low contact angle values indicate that the liquid spreads or wets well, while high values indicate poor wetting or non-wetting. Contact angles are estimated in the lab by measuring the weight of the meniscus formed at the air-liquid-quartz interface and by knowing the fluid surface tension. In the lab, we have been able to use low-frequency seismic attenuation data to detect changes in the wetting characteristics of glass plates and of Berea sandstone. The accepted seismic attenuation mechanism is related to the loss of seismic energy due to the hysteresis of meniscus movement (wetting hysteresis) when a pore containing two fluids is stressed at very low frequencies (measuring low-frequency seismic attenuation in the lab while flowing bacteria solution through Berea sandstone and we are testing this application in the field.

  6. Advances in dynamic and mean field games theory, applications, and numerical methods

    CERN Document Server

    Viscolani, Bruno

    2017-01-01

    This contributed volume considers recent advances in dynamic games and their applications, based on presentations given at the 17th Symposium of the International Society of Dynamic Games, held July 12-15, 2016, in Urbino, Italy. Written by experts in their respective disciplines, these papers cover various aspects of dynamic game theory including mean-field games, stochastic and pursuit-evasion games, and computational methods for dynamic games. Topics covered include Pedestrian flow in crowded environments Models for climate change negotiations Nash Equilibria for dynamic games involving Volterra integral equations Differential games in healthcare markets Linear-quadratic Gaussian dynamic games Aircraft control in wind shear conditions Advances in Dynamic and Mean-Field Games presents state-of-the-art research in a wide spectrum of areas. As such, it serves as a testament to the continued vitality and growth of the field of dynamic games and their applications. It will be of interest to an interdisciplinar...

  7. Influence of time dependent longitudinal magnetic fields on the cooling process, exchange bias and magnetization reversal mechanism in FM core/AFM shell nanoparticles: a Monte Carlo study.

    Science.gov (United States)

    Yüksel, Yusuf; Akıncı, Ümit

    2016-12-07

    Using Monte Carlo simulations, we have investigated the dynamic phase transition properties of magnetic nanoparticles with ferromagnetic core coated by an antiferromagnetic shell structure. Effects of field amplitude and frequency on the thermal dependence of magnetizations, magnetization reversal mechanisms during hysteresis cycles, as well as on the exchange bias and coercive fields have been examined, and the feasibility of applying dynamic magnetic fields on the particle have been discussed for technological and biomedical purposes.

  8. Hysteresis in pressure-driven DNA denaturation.

    Directory of Open Access Journals (Sweden)

    Enrique Hernández-Lemus

    Full Text Available 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.

  9. Mechanism of Wettability Hysteresis in Natural Soils

    Science.gov (United States)

    Ryder, J. L.; Demond, A. H.

    2006-12-01

    Because models of subsurface flow and transport depend on the contact angles made by the air/water and waste liquid/water interfaces with soil and rock surfaces, accurate knowledge of the wettability of subsurface systems is necessary. Sessile drop contact angles were measured on dry rock surfaces and on the same rock surfaces immersed in a second fluid. Quartz slides and cut rock faces that had been leveled and polished served as representative surfaces for silica sand, talc, kerogen containing shales, bituminous coal, and mineralized carbon. For several carbon-containing materials, contact angles are reversed from near 170 degrees when water is the receding fluid to less than 70 degrees if water is the advancing fluid. However, some mineral soils do not display wetting reversal. This work seeks to explain the mechanisms of the wetting order hysteresis. Utilizing an aqueous 0.01 M NaCl solution, glycerol, 1-bromonapthalene, and diidomethane as probe fluids, contact angle values are assessed with the method of van Oss et al. (1988) to determine the surface energy components of each type of soil. The quartz mineral surface energy has a large polar component and the calculated quartz surface energy does not depend on the wetting history of the slide. However, the magnitudes of the surface energy components of the carbon-containing materials change depending on the wetting history, indicating that the nature of the surface is altered by the surrounding fluid. The presence of wetting order hysteresis may contribute to the heterogeneous fluid distributions found at many waste liquid sites. When soil is known to contain carbon, some knowledge of the wetting history is necessary to predict the contact angle and thus the transport behavior.

  10. Contact angle hysteresis: a review of fundamentals and applications

    NARCIS (Netherlands)

    Eral, Burak; 't Mannetje, Dieter; Oh, J.M.

    2013-01-01

    Contact angle hysteresis is an important physical phenomenon. It is omnipresent in nature and also plays a crucial role in various industrial processes. Despite its relevance, there is a lack of consensus on how to incorporate a description of contact angle hysteresis into physical models. To

  11. Carnot cycle for magnetic materials: The role of hysteresis

    International Nuclear Information System (INIS)

    Sasso, Carlo P.; Basso, Vittorio; LoBue, Martino; Bertotti, Giorgio

    2006-01-01

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

  12. Dynamical implications of sample shape for avalanches in 2-dimensional random-field Ising model with saw-tooth domain wall

    Science.gov (United States)

    Tadić, Bosiljka

    2018-03-01

    We study dynamics of a built-in domain wall (DW) in 2-dimensional disordered ferromagnets with different sample shapes using random-field Ising model on a square lattice rotated by 45 degrees. The saw-tooth DW of the length Lx is created along one side and swept through the sample by slow ramping of the external field until the complete magnetisation reversal and the wall annihilation at the open top boundary at a distance Ly. By fixing the number of spins N =Lx ×Ly = 106 and the random-field distribution at a value above the critical disorder, we vary the ratio of the DW length to the annihilation distance in the range Lx /Ly ∈ [ 1 / 16 , 16 ] . The periodic boundary conditions are applied in the y-direction so that these ratios comprise different samples, i.e., surfaces of cylinders with the changing perimeter Lx and height Ly. We analyse the avalanches of the DW slips between following field updates, and the multifractal structure of the magnetisation fluctuation time series. Our main findings are that the domain-wall lengths materialised in different sample shapes have an impact on the dynamics at all scales. Moreover, the domain-wall motion at the beginning of the hysteresis loop (HLB) probes the disorder effects resulting in the fluctuations that are significantly different from the large avalanches in the central part of the loop (HLC), where the strong fields dominate. Specifically, the fluctuations in HLB exhibit a wide multi-fractal spectrum, which shifts towards higher values of the exponents when the DW length is reduced. The distributions of the avalanches in this segments of the loops obey power-law decay and the exponential cutoffs with the exponents firmly in the mean-field universality class for long DW. In contrast, the avalanches in the HLC obey Tsallis density distribution with the power-law tails which indicate the new categories of the scale invariant behaviour for different ratios Lx /Ly. The large fluctuations in the HLC, on the other

  13. An Exploration of the System Dynamics Field : A Model-Based Policy Analysis

    NARCIS (Netherlands)

    Rose, A.C.

    2014-01-01

    This report presents a first look study at the field of System Dynamics. The objective of the study is to perform a model-based policy analysis in order to investigate the future advancement of the System Dynamics field. The aim of this investigation is to determine what this advancement should look

  14. Dynamics of fermions and inhomogeneous Bose fields on a spacetime lattice

    NARCIS (Netherlands)

    dr Aarts, G.A.P.T.; Smit, J.

    1999-01-01

    The dynamics of the $1+1$ abelian Higgs model with fermions is studied in the large $N_f$ approximation, on a real-time lattice. The Bose fields obey effective classical equations of motion which include the fermion back reaction. The dynamics of the quantized fermion field is treated with a mode

  15. Family in Focus: On Design and Field Trial of the Dynamic Collage [DC

    NARCIS (Netherlands)

    René Bakker; Koen van Turnhout; Jasper Jeurens

    2014-01-01

    In this paper we present the design and field trial of the Dynamic Collage. The Dynamic Collage was designed to facilitate and to stimulate participation of family members in the informal care of an elderly person. The Dynamic Collage enabled relatives to update their current activity by sending a

  16. Quantum dynamical phenomena of independent electrons in semiconductor superlattices subject to a uniform electric field

    International Nuclear Information System (INIS)

    Bouchard, A.M.

    1994-01-01

    This report discusses the following topics: Bloch oscillations and other dynamical phenomena of electrons in semiconductor superlattices; solvable dynamical model of an electron in a one-dimensional aperiodic lattice subject to a uniform electric field; and quantum dynamical phenomena of electrons in aperiodic semiconductor superlattices

  17. Coexistence of negative photoconductivity and hysteresis in semiconducting graphene

    Energy Technology Data Exchange (ETDEWEB)

    Zhuang, Shendong; Tang, Nujiang; Chen, Zhuo, E-mail: zchen@nju.edu.cn [School of Physics, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, Nanjing University, No. 22 Hankou Road, Nanjing, Jiangsu, 210093 (China); Chen, Yan; Xia, Yidong [Department of Materials Science and Engineering, National Laboratory of Solid State Microstructures, and Collaborative Innovation Center of Advanced Microstructures, No. 22 Hankou Road, Nanjing University, Nanjing, Jiangsu, 210093 (China); Xu, Xiaoyong; Hu, Jingguo, E-mail: jghu@yzu.edu.cn [School of Physics Science and Technology, Yangzhou University, No. 180 Siwangting Road, Yangzhou, Jiangsu, 225002 (China)

    2016-04-15

    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.

  18. Coexistence of negative photoconductivity and hysteresis in semiconducting graphene

    Directory of Open Access Journals (Sweden)

    Shendong Zhuang

    2016-04-01

    Full Text Available 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.

  19. Dynamics of valence-shell electrons and nuclei probed by strong-field holography and rescattering

    Science.gov (United States)

    Walt, Samuel G.; Bhargava Ram, Niraghatam; Atala, Marcos; Shvetsov-Shilovski, Nikolay I; von Conta, Aaron; Baykusheva, Denitsa; Lein, Manfred; Wörner, Hans Jakob

    2017-01-01

    Strong-field photoelectron holography and laser-induced electron diffraction (LIED) are two powerful emerging methods for probing the ultrafast dynamics of molecules. However, both of them have remained restricted to static systems and to nuclear dynamics induced by strong-field ionization. Here we extend these promising methods to image purely electronic valence-shell dynamics in molecules using photoelectron holography. In the same experiment, we use LIED and photoelectron holography simultaneously, to observe coupled electronic-rotational dynamics taking place on similar timescales. These results offer perspectives for imaging ultrafast dynamics of molecules on femtosecond to attosecond timescales. PMID:28643771

  20. Fast-forward of quantum adiabatic dynamics in electro-magnetic field

    OpenAIRE

    Masuda, Shumpei; Nakamura, Katsuhiro

    2010-01-01

    We show a method to accelerate quantum adiabatic dynamics of wavefunctions under electro-magnetic field by developing the previous theory (Masuda & Nakamura 2008 and 2010). Firstly we investigate the orbital dynamics of a charged particle. We derive the driving field which accelerates quantum adiabatic dynamics in order to obtain the final adiabatic states except for the spatially uniform phase such as the adiabatic phase in any desired short time. Fast-forward of adiabatic squeezing and tran...

  1. Electron dynamics in metals and semiconductors in strong THz fields

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd

    2017-01-01

    Semiconductors and metals respond to strong electric fields in a highly nonlinear fashion. Using single-cycle THz field transients it is possible to investigate this response in regimes not accessible by transport-based measurements. Extremely high fields can be applied without material damage...

  2. Quantum mechanics and the second law of thermodynamics: an insight gleaned from magnetic hysteresis in the first order phase transition of an isolated mesoscopic-size type I superconductor

    Science.gov (United States)

    Keefe, Peter D.

    2012-11-01

    J Bardeen proposed that the adiabatic phase transition of mesoscopic-size type I superconductors must be accompanied by magnetic hysteresis in the critical magnetic field of sufficient magnitude to satisfy the second law of thermodynamics, herein referred to as ‘Bardeen Hysteresis’. Bardeen Hysteresis remains speculative in that it has not been reported in the literature. This paper investigates Bardeen Hysteresis as a possible accompaniment to the adiabatic phase transition of isolated mesoscopic-size type I superconductors and its implications with respect to the second law of thermodynamics. A causal mechanism for Bardeen Hysteresis is discussed which contrasts with the long accepted causal mechanism of magnetic hysteresis, as first summarized by Pippard, herein referred to as ‘Pippard Hysteresis’. The paper offers guidance for an experimental verification and comments on how the existence of Bardeen Hysteresis has relation to a quantum mechanical basis for the second law of thermodynamics.

  3. Quantum mechanics and the second law of thermodynamics: an insight gleaned from magnetic hysteresis in the first order phase transition of an isolated mesoscopic-size type I superconductor

    International Nuclear Information System (INIS)

    Keefe, Peter D

    2012-01-01

    J Bardeen proposed that the adiabatic phase transition of mesoscopic-size type I superconductors must be accompanied by magnetic hysteresis in the critical magnetic field of sufficient magnitude to satisfy the second law of thermodynamics, herein referred to as ‘Bardeen Hysteresis’. Bardeen Hysteresis remains speculative in that it has not been reported in the literature. This paper investigates Bardeen Hysteresis as a possible accompaniment to the adiabatic phase transition of isolated mesoscopic-size type I superconductors and its implications with respect to the second law of thermodynamics. A causal mechanism for Bardeen Hysteresis is discussed which contrasts with the long accepted causal mechanism of magnetic hysteresis, as first summarized by Pippard, herein referred to as ‘Pippard Hysteresis’. The paper offers guidance for an experimental verification and comments on how the existence of Bardeen Hysteresis has relation to a quantum mechanical basis for the second law of thermodynamics.

  4. Attosecond Electron Wave Packet Dynamics in Strong Laser Fields

    International Nuclear Information System (INIS)

    Johnsson, P.; Remetter, T.; Varju, K.; L'Huillier, A.; Lopez-Martens, R.; Valentin, C.; Balcou, Ph.; Kazamias, S.; Mauritsson, J.; Gaarde, M. B.; Schafer, K. J.; Mairesse, Y.; Wabnitz, H.; Salieres, P.

    2005-01-01

    We use a train of sub-200 attosecond extreme ultraviolet (XUV) pulses with energies just above the ionization threshold in argon to create a train of temporally localized electron wave packets. We study the energy transfer from a strong infrared (IR) laser field to the ionized electrons as a function of the delay between the XUV and IR fields. When the wave packets are born at the zero crossings of the IR field, a significant amount of energy (∼20 eV) is transferred from the field to the electrons. This results in dramatically enhanced above-threshold ionization in conditions where the IR field alone does not induce any significant ionization. Because both the energy and duration of the wave packets can be varied independently of the IR laser, they are valuable tools for studying and controlling strong-field processes

  5. A system for controllable magnetic measurements of hysteresis and Barkhausen noise

    Czech Academy of Sciences Publication Activity Database

    Stupakov, Oleksandr; Perevertov, Oleksiy; Zablotskyy, Vitaliy A.

    2016-01-01

    Roč. 65, č. 5 (2016), s. 1087-1097 ISSN 0018-9456. [IEEE International Instrumentation and Measurement Technology Conference (I2MTC 2015). Pisa, 11.05.2015-14.05.2015] R&D Projects: GA ČR GA13-18993S Institutional support: RVO:68378271 Keywords : Barkhausen effect * feedback circuits * magnetic field measurement * magnetic hysteresis * magnetization processes * silicon steel Subject RIV: JB - Sensors, Measurment, Regulation Impact factor: 2.456, year: 2016

  6. Effective field theory with differential operator technique for dynamic phase transition in ferromagnetic Ising model

    International Nuclear Information System (INIS)

    Kinoshita, Takehiro; Fujiyama, Shinya; Idogaki, Toshihiro; Tokita, Masahiko

    2009-01-01

    The non-equilibrium phase transition in a ferromagnetic Ising model is investigated by use of a new type of effective field theory (EFT) which correctly accounts for all the single-site kinematic relations by differential operator technique. In the presence of a time dependent oscillating external field, with decrease of the temperature the system undergoes a dynamic phase transition, which is characterized by the period averaged magnetization Q, from a dynamically disordered state Q = 0 to the dynamically ordered state Q ≠ 0. The results of the dynamic phase transition point T c determined from the behavior of the dynamic magnetization and the Liapunov exponent provided by EFT are improved than that of the standard mean field theory (MFT), especially for the one dimensional lattice where the standard MFT gives incorrect result of T c = 0 even in the case of zero external field.

  7. Field-based dynamic light scattering microscopy: theory and numerical analysis.

    Science.gov (United States)

    Joo, Chulmin; de Boer, Johannes F

    2013-11-01

    We present a theoretical framework for field-based dynamic light scattering microscopy based on a spectral-domain optical coherence phase microscopy (SD-OCPM) platform. SD-OCPM is an interferometric microscope capable of quantitative measurement of amplitude and phase of scattered light with high phase stability. Field-based dynamic light scattering (F-DLS) analysis allows for direct evaluation of complex-valued field autocorrelation function and measurement of localized diffusive and directional dynamic properties of biological and material samples with high spatial resolution. In order to gain insight into the information provided by F-DLS microscopy, theoretical and numerical analyses are performed to evaluate the effect of numerical aperture of the imaging optics. We demonstrate that sharp focusing of fields affects the measured diffusive and transport velocity, which leads to smaller values for the dynamic properties in the sample. An approach for accurately determining the dynamic properties of the samples is discussed.

  8. Hysteresis compensation of photoluminescence in ZnS:Cu for noncontact shaft torque sensing.

    Science.gov (United States)

    Cho, Min-Young; Kim, Ji-Sik; Kim, Gi-Woo

    2016-03-01

    This paper presents a preliminary investigation of loading rate-dependent hysteresis of photoluminescence (PL) by phosphorescence quenching of copper-doped zinc sulfide (ZnS:Cu) microparticles in response to dynamic torsional loading. Precision sinusoidal torque waveforms in the frequency range of 0.5-3 Hz are used to identify the loading rate-dependent (i.e., frequency-dependent) nonlinear hysteresis phenomenon. The potential of the application of PL is demonstrated by successfully measuring the sinusoidal torque applied to a rotational shaft by evaluating the loading rate-dependent PL intensity signature using a photomultiplier tube. In addition, the potential of noncontact shaft torque sensing is demonstrated successfully by the simple compensation derived from ad hoc heuristic characterization.

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

    Science.gov (United States)

    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

  10. Hysteresis loops of Cosmic Ray intensity decreases versus solar and interplanetary parameters

    Directory of Open Access Journals (Sweden)

    R. P. Kane

    2007-10-01

    Full Text Available The purpose of this study was to examine the correlation between CR (Cosmic Ray intensity and solar, interplanetary and terrestrial parameters. The hysteresis loops of (CR versus those of several solar parameters showed narrow loops in even cycles 20, 22 and broad loops in odd cycles 19, 21, as also in the recent odd cycle 23. Hysteresis plots for CR versus interplanetary number density N and speed V were erratic and uncertain (broad and narrow, all mixed up. Plots of CR versus Interplanetary magnetic field (IMF B seemed to be narrow for even as well as odd cycles. Hysteresis loops between CR and other interplanetary parameters were not clear-cut. The same was true for terrestrial parameters. During sunspot maximum years 2000–2003 of cycle 23, there is a double peak structure in all parameters. Whereas CR have a peak spacing of ~30 months, sunspots and Tilt angle have a spacing of only ~20 months. The solar open magnetic flux and the Voyager 1 magnetic field have a spacing of ~25 months. The solar polar magnetic field reverses later than the first peak of all parameters and hence, could not be a direct cause (as if effect started before the cause and lasted for several months more after the cause disappeared. It seems that CR modulation is mainly guided by magnetic configurations deep in the heliosphere, which may not have a simple relationship with parameters near Earth or near Sun.

  11. Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field

    Science.gov (United States)

    Bojarevics, V.; Easter, S.; Pericleous, K.

    2012-01-01

    Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case.

  12. Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

    Directory of Open Access Journals (Sweden)

    Torres C.

    2013-01-01

    Full Text Available 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.

  13. Dynamics of underdamped Josephson arrays in a magnetic field

    International Nuclear Information System (INIS)

    Octavio, M.; Whan, C.B.; Geigenmueller, U.; Lobb, C.J.

    1994-01-01

    We present simulations of the dynamics of underdamped classical Josephson arrays for values of the flux quanta per unit cell f=1/2. We find the dynamics of this system to be quite rich. The I-V characteristics are found to have two distinct regime as the damping is increased. At low voltages the current-voltage characteristics exhibit a regime which we characterize as flux-flow-like since it is dominated by the motion of the vortex superlattice. This regime may exhibit chaotic-like behavior as the damping parameter is increased. At high voltages the characteristics jump to an ohmic-like state in which the junctions are all oscillating. We present a potential model which is quite useful in understanding the dynamics of the system. (orig.)

  14. Fourier transform and controlling of flux in scalar hysteresis measurement

    International Nuclear Information System (INIS)

    Kuczmann, Miklos

    2008-01-01

    The paper deals with a possible realization of eliminating the effect of noise in scalar hysteresis measurements. The measured signals have been transformed into the frequency domain, and, after applying digital filter, the spectrums of the filtered signals have been transformed back to the time domain. The proposed technique results in an accurate noise-removal algorithm. The paper illustrates a fast controlling algorithm applying the inverse of the actually measured hysteresis loop, and another proportional one to measure distorted flux pattern. By developing the mentioned algorithms, it aims at the controlling of a more complicated phenomena, i.e. measuring the vector hysteresis characteristics

  15. High contact angle hysteresis of superhydrophobic surfaces: Hydrophobic defects

    Science.gov (United States)

    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.

  16. Resonances and reactions from mean-field dynamics

    Directory of Open Access Journals (Sweden)

    Stevenson P. D.

    2016-01-01

    Full Text Available The time-dependent version of nuclear density functional theory, using functionals derived from Skyrme interactions, is able to approximately describe nuclear dynamics. We present time-dependent results of calculations of dipole resonances, concentrating on excitations of valence neutrons against a proton plus neutron core in the neutron-rich doubly-magic 132Sn nucleus, and results of collision dynamics, highlighting potential routes to ternary fusion, with the example of a collision of 48Ca+48Ca+208Pb resulting in a compound nucleus of element 120 stable against immediate fission.

  17. Titration and hysteresis in epigenetic chromatin silencing

    Science.gov (United States)

    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.

  18. Titration and hysteresis in epigenetic chromatin silencing

    International Nuclear Information System (INIS)

    Dayarian, Adel; Sengupta, Anirvan M

    2013-01-01

    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. (paper)

  19. High frequency monitoring of pesticides in runoff water from a vineyard: ecotoxicological and hysteresis pattern analysis

    Science.gov (United States)

    Lefrancq, Marie; Jadas-Hécart, Alain; La Jeunesse, Isabelle; Landry, David; Payraudeau, Sylvain

    2017-04-01

    Rainfall-induced peaks in pesticide concentrations can occur rapidly; therefore, low frequency sampling may largely underestimate maximum pesticide concentrations and fluxes. Detailed storm-based sampling of pesticide concentrations in runoff water to better predict pesticide sources, transport pathways and toxicity within the headwater catchments is actually lacking. High frequency monitoring (2 min) of dissolved concentrations and loads for seven pesticides (Dimetomorph, Fluopicolide, Glyphosate, Iprovalicarb, Tebuconazole, Tetraconazole and Triadimenol) and one degradation product (AMPA) were assessed for 20 runoff events from 2009 to 2012 at the outlet of a vineyard catchment in the Layon catchment in France. The pesticide concentrations reached 387 µg/L. All of the runoff events exceeded the mandated acceptable concentrations of 0.1 µg/L for each pesticide (European directive 2013/39/EC). High resolution sampling used to detect the peak pesticide levels revealed that Toxic Units (TU) for algae, invertebrates and fish often exceeded the European Uniform principles (25%). The instantaneous and average (time or discharge-weighted) concentrations indicated an up to 30- or 4-fold underestimation of the TU obtained when measuring the maximum concentrations, respectively, highlighting the important role of the sampling methods for assessing peak exposure. High resolution sampling combined with concentration-discharge hysteresis analyses revealed that clockwise responses were predominant (52%), indicating that Hortonian runoff is the prevailing surface runoff trigger mechanism in the study catchment. The hysteresis patterns for suspended solids and pesticides were highly dynamic and storm- and chemical-dependent. Intense rainfall events induced stronger C-Q hysteresis (magnitude). This study provides new insights into the complexity of pesticide dynamics in runoff water and highlights the ability of hysteresis analysis to improve the understanding of pesticide

  20. Hamiltonian dynamics of purely affine fields (Einstein-Schroedinger Theory)

    Science.gov (United States)

    Treder, H.-J.

    The Lagrangian of the general-relativistic affine field theory of the non-symmetric connection field is the Schroedinger scalar density and the field variables (canonical coordinates) are Einstein's affine tensors. The field equations are the Einstein-Schroedinger equations, and the minors give by definition gmn = lambda-1Rmn, and lambda becomes the cosmological constant. The Hamiltonian density is the upsilon00-component of the Einstein energy-momentum complex, and the tensor-density components are the canonically conjugated momentum densities of the field coordinates. The canonical equations are (-g)-1/2Nlmnupsilon00 = 0, and we have no constraints. The affine field theory is invariant with respect to all transformations which preserve the Levi-Civita parallelism (Einstein's unified T-A group), and the field equations possess transposition invariance. The symmetry conditions Gammaimn = Gamma inm reduce the space to the general-relativistic Einstein spaces with Rik = Rki. The equation Rik = lambda gik yields Gammaikl = vector (i kl), and the pathes of test particles define geodesic world lines of the Einstein spaces.

  1. Real-Space Application of the Mean-Field Description of Spin-Glass Dynamics

    International Nuclear Information System (INIS)

    Barrat, Alain; Berthier, Ludovic

    2001-01-01

    The out of equilibrium dynamics of finite dimensional spin glasses is considered from a point of view going beyond the standard 'mean-field theory' versus 'droplet picture' debate of the past decades. The main predictions of both theories concerning the spin-glass dynamics are discussed. It is shown, in particular, that predictions originating from mean-field ideas concerning the violations of the fluctuation-dissipation theorem apply quantitatively, provided one properly takes into account the role of a spin-glass coherence length, which plays a central role in the droplet picture. Dynamics in a uniform magnetic field is also briefly discussed

  2. Lattice Boltzmann modeling of contact angle and its hysteresis in two-phase flow with large viscosity difference.

    Science.gov (United States)

    Liu, Haihu; Ju, Yaping; Wang, Ningning; Xi, Guang; Zhang, Yonghao

    2015-09-01

    Contact angle hysteresis is an important physical phenomenon omnipresent in nature and various industrial processes, but its effects are not considered in many existing multiphase flow simulations due to modeling complexity. In this work, a multiphase lattice Boltzmann method (LBM) is developed to simulate the contact-line dynamics with consideration of the contact angle hysteresis for a broad range of kinematic viscosity ratios. In this method, the immiscible two-phase flow is described by a color-fluid model, in which the multiple-relaxation-time collision operator is adopted to increase numerical stability and suppress unphysical spurious currents at the contact line. The contact angle hysteresis is introduced using the strategy proposed by Ding and Spelt [Ding and Spelt, J. Fluid Mech. 599, 341 (2008)JFLSA70022-112010.1017/S0022112008000190], and the geometrical wetting boundary condition is enforced to obtain the desired contact angle. This method is first validated by simulations of static contact angle and dynamic capillary intrusion process on ideal (smooth) surfaces. It is then used to simulate the dynamic behavior of a droplet on a nonideal (inhomogeneous) surface subject to a simple shear flow. When the droplet remains pinned on the surface due to hysteresis, the steady interface shapes of the droplet quantitatively agree well with the previous numerical results. Four typical motion modes of contact points, as observed in a recent study, are qualitatively reproduced with varying advancing and receding contact angles. The viscosity ratio is found to have a notable impact on the droplet deformation, breakup, and hysteresis behavior. Finally, this method is extended to simulate the droplet breakup in a microfluidic T junction, with one half of the wall surface ideal and the other half nonideal. Due to the contact angle hysteresis, the droplet asymmetrically breaks up into two daughter droplets with the smaller one in the nonideal branch channel, and the

  3. Lattice Boltzmann modeling of contact angle and its hysteresis in two-phase flow with large viscosity difference

    Science.gov (United States)

    Liu, Haihu; Ju, Yaping; Wang, Ningning; Xi, Guang; Zhang, Yonghao

    2015-09-01

    Contact angle hysteresis is an important physical phenomenon omnipresent in nature and various industrial processes, but its effects are not considered in many existing multiphase flow simulations due to modeling complexity. In this work, a multiphase lattice Boltzmann method (LBM) is developed to simulate the contact-line dynamics with consideration of the contact angle hysteresis for a broad range of kinematic viscosity ratios. In this method, the immiscible two-phase flow is described by a color-fluid model, in which the multiple-relaxation-time collision operator is adopted to increase numerical stability and suppress unphysical spurious currents at the contact line. The contact angle hysteresis is introduced using the strategy proposed by Ding and Spelt [Ding and Spelt, J. Fluid Mech. 599, 341 (2008), 10.1017/S0022112008000190], and the geometrical wetting boundary condition is enforced to obtain the desired contact angle. This method is first validated by simulations of static contact angle and dynamic capillary intrusion process on ideal (smooth) surfaces. It is then used to simulate the dynamic behavior of a droplet on a nonideal (inhomogeneous) surface subject to a simple shear flow. When the droplet remains pinned on the surface due to hysteresis, the steady interface shapes of the droplet quantitatively agree well with the previous numerical results. Four typical motion modes of contact points, as observed in a recent study, are qualitatively reproduced with varying advancing and receding contact angles. The viscosity ratio is found to have a notable impact on the droplet deformation, breakup, and hysteresis behavior. Finally, this method is extended to simulate the droplet breakup in a microfluidic T junction, with one half of the wall surface ideal and the other half nonideal. Due to the contact angle hysteresis, the droplet asymmetrically breaks up into two daughter droplets with the smaller one in the nonideal branch channel, and the behavior of

  4. Complex dynamics of a particle in an oscillating potential field

    Indian Academy of Sciences (India)

    Barnali Pal

    2017-07-25

    Jul 25, 2017 ... time-dependent Hamiltonian systems lead to significant advances towards a qualitative and quantitative under- standing of their behaviour over a long time. In many cases, the chaotic dynamics of a particle inside the driven potential leads to very interesting phenomena, including power-law distribution for ...

  5. Transport hysteresis and zonal flow stimulation in magnetized plasmas

    Science.gov (United States)

    Gravier, E.; Lesur, M.; Reveille, T.; Drouot, T.; Médina, J.

    2017-12-01

    A hysteresis in the relationship between zonal flows and electron heating is observed numerically by using gyrokinetic simulations in fusion plasmas. As the electron temperature increases, a first transition occurs, at a given electron/ion temperature ratio, above which zonal flows are much weaker than before the transition, leading to a poorly confined plasma. Beyond this transition, even if the electron temperature is lowered to a moderate value, the plasma fails to recover a dynamic state with strong zonal flows. Then, as the electron temperature decreases further, a new transition appears, at a temperature lower than the first transition, below which the zonal flows are stronger than they were initially. The confinement of the plasma and the heat flux are thus found to be sensitive to the history of the magnetized plasma. These transitions are associated with large exchanges of energy between the modes corresponding to instabilities ( m> 0 ) and zonal flows ( m = 0 ). We also observe that up to the first transition it is possible to use a control method to stimulate the appearance of zonal flows and therefore the confinement of the plasma. Beyond that transition, this control method is no longer effective.

  6. Backward bifurcation and hysteresis in models of recurrent tuberculosis.

    Science.gov (United States)

    Wangari, Isaac Mwangi; Stone, Lewi

    2018-01-01

    An epidemiological model is presented that provides a comprehensive description of the transmission pathways involved for recurrent tuberculosis (TB), whereby cured individuals can become reinfected. Our main goal is to determine conditions that lead to the appearance of a backward bifurcation. This occurs when an asymptotically stable infection free equilibrium concurrently exists with a stable non-trivial equilibria even though the basic reproduction number R0 is less than unity. Although, some 10-30% cases of TB are recurrent, the role of recurrent TB as far as the formation of backward bifurcation is concerned, is rarely if ever studied. The model used here incorporates progressive primary infection, exogenous reinfection, endogenous reactivation and recurrent TB as transmission mechanisms that contribute to TB progression. Unlike other studies of TB dynamics that make use of frequency dependent transmission rates, our analysis provides exact backward bifurcation threshold conditions without resorting to commonly applied approximations and simplifying assumptions. Exploration of the model through analytical and numerical analysis reveal that recurrent TB is sometimes capable of triggering hysteresis effects which allow TB to persist when R0 < 1 even though there is no backward bifurcation. Furthermore, recurrent TB can independently induce backward bifurcation phenomena if it exceeds a certain threshold.

  7. Nonlinear reversed field pinch dynamics with nonideal boundaries

    International Nuclear Information System (INIS)

    Ho, Y.L.; Prager, S.C.

    1991-03-01

    The nonlinear behavior of the reversed field pinch bounded by a resistive shell or a distant conducting wall is investigated with a three-dimensional magnetohydrodynamic code. Nonlinear interaction between modes enhances fluctuation levels as the conducting wall is removed. The enhanced fluctuation induced v x b electric field, which produces the dynamo effect, suppresses toroidal current and enhances surface helicity dissipation. Thus, loop voltage must increase to sustain the current and maintain helicity balance. 46 refs., 21 figs., 2 tabs

  8. Charged Particle Dynamics in a Magnetodisc-Field Structure

    Science.gov (United States)

    Guio, P.; O'Brien, W.; Achilleos, N. A.; Arridge, C. S.

    2016-12-01

    The Earth's internal magnetic field is to a good approximation dipolar, and charged particles from the magnetosphere, depending on their kinetic energy, pitch angle and distance can remain trapped in this field. The motion of such trapped particles is characterised by their bounce, drift and cyclotron (gyration) periods. High-energy electron and proton populations in the two radiation (van Allen) belts are such examples.At the gas giants, Jupiter and Saturn, the total magnetic field deviates from a dipolar configuration due to internal sources of plasma provided by the moons Io and Enceladus respectively. In addition, the rapid rotation of these planets (period of order 10h) plays a role in the development of a disk-like field structure near the equator where centrifugal force is dominant - a configuration referred to as a magnetodisc.We present results of numerical simulations of charged particle motion in such a magnetodisc field structure using particle tracing and the UCL Magnetodisc Model, and we use these simulations to characterise and quantify the differences between particle motion in magnetodisc and dipole fields.

  9. The magnetic field dependent dynamic properties of magnetorheological elastomers based on hard magnetic particles

    Science.gov (United States)

    Wen, Qianqian; Wang, Yu; Gong, Xinglong

    2017-07-01

    In this study, novel magnetorheological elastomers based on hard magnetic particles (H-MREs) were developed and the magnetic field dependent dynamic properties of the H-MREs were further investigated. The storage modulus of H-MREs could not only be increased by increasing magnetic field but also be decreased by the increasing magnetic field of opposite orientation. For the anisotropic H-MREs with 80 wt% NdFeB particles, the field-induced increasing and decreasing modulus was 426 kPa and 118 kPa respectively. Moreover, the dynamic performances of H-MREs significantly depended on the pre-structure magnetic field, magnetizing field and test magnetic field. The H-MREs were initially magnetized and formed the chain-like microstructure by the pre-structure magnetic field. The field-induced increasing and decreasing modulus of H-MREs both raised with increasing of the magnetizing field. When the magnetizing field increased from 400 to 1200 kA m-1, the field induced decreasing modulus of the 80 wt% isotropic H-MREs raised from 3 to 47 kPa. The magnetic field dependent curves of H-MREs’ storage modulus were asymmetric if the magnetizing field was higher than the test magnetic field. Based on the dipolar model of MREs and magnetic properties of hard magnetic material, a reasonable explanation was proposed to understand the H-MREs’ field dependent mechanical behaviors.

  10. Remotely Sensing Larval Population Dynamics of Rice Field Anophelines

    Science.gov (United States)

    Beck, Louisa R.; Dister, Sheri W.; Wood, Byron L.; Washino, Robert K.

    1997-01-01

    The primary objective of both studies was to determine if RS and GIS techniques could be used to distinguish between high and low larval-producing rice fields in California. Results of the first study suggested that early-season green-up and proximity to livestock pastures were positively correlated with high larval abundance. Based on the early-season spectral differences between high and low larval-producing fields, it appeared that canopy development and tillering influenced mosquito habitat quality. At that time, rice fields consisted of a mixture of plants and water, a combination that allowed An. freeborni females to lay eggs in partial sunlight, protected from both predators and wind. This established a population earlier in the season than in other, 'less-green' fields where tillering and plant emergence was too minimal for ovipositioning. The study also indicated the importance of the distance that a mosquito would have to fly in order to take a bloodmeal prior to ovipositing. These associations were fully explored in an expanded study two years later. The second study confirmed the positive relationship between early season canopy development and larval abundance, and also demonstrated the relationship between abundance and distance-to-pasture. The association between greenness (as measured using NDVI), distance-to-pasture, and abundance is illustrated. The second study also indicated the siginificance of the landscape context of rice fields for larval production. Fields that included opportunities for feeding and resting within the flight range of the mosquito had higher abundances than did fields that were in a homogeneous rice area.

  11. Effective-field theory on the kinetic Ising model

    International Nuclear Information System (INIS)

    Shi Xiaoling; Wei Guozhu; Li Lin

    2008-01-01

    As an analytical method, the effective-field theory (EFT) is used to study the dynamical response of the kinetic Ising model in the presence of a sinusoidal oscillating field. The effective-field equations of motion of the average magnetization are given for the square lattice (Z=4) and the simple cubic lattice (Z=6), respectively. The dynamic order parameter, the hysteresis loop area and the dynamic correlation are calculated. In the field amplitude h 0 /ZJ-temperature T/ZJ plane, the phase boundary separating the dynamic ordered and the disordered phase has been drawn, and the dynamical tricritical point has been observed. We also make the compare results of EFT with that given by using the mean field theory (MFT)

  12. Nonlinear dynamics of a magnetically driven Duffing-type spring–magnet oscillator in the static magnetic field of a coil

    International Nuclear Information System (INIS)

    Donoso, Guillermo; Ladera, Celso L

    2012-01-01

    We study the nonlinear oscillations of a forced and weakly dissipative spring–magnet system moving in the magnetic fields of two fixed coaxial, hollow induction coils. As the first coil is excited with a dc current, both a linear and a cubic magnet-position dependent force appear on the magnet–spring system. The second coil, located below the first, excited with an ac current, provides the oscillating magnetic driving force on the system. From the magnet–coil interactions, we obtain, analytically, the nonlinear motion equation of the system, found to be a forced and damped cubic Duffing oscillator moving in a quartic potential. The relative strengths of the coefficients of the motion equation can be easily set by varying the coils’ dc and ac currents. We demonstrate, theoretically and experimentally, the nonlinear behaviour of this oscillator, including its oscillation modes and nonlinear resonances, the fold-over effect, the hysteresis and amplitude jumps, and its chaotic behaviour. It is an oscillating system suitable for teaching an advanced experiment in nonlinear dynamics both at senior undergraduate and graduate levels. (paper)

  13. On-the-fly, electric-field-driven, coupled electron-nuclear dynamics.

    Science.gov (United States)

    Jones, Garth A; Acocella, Angela; Zerbetto, Francesco

    2008-10-09

    An on-the-fly, electric field driven, coupled electron-nuclear dynamics approach is developed and applied to model the photodissociation of water in the A((1)B1) excited state. In this method, a quantum propagator evolves the photon-induced electronic dynamics in the ultrafast time scale, and a quasi-classical surface hopping approach describes the nuclear dynamics in the slower time scale. In addition, strong system-field interactions are explicitly included in the electronic propagator. This theoretical development enables us to study rapid photon-induced bond dissociation dynamics and demonstrates the partial breakdown of electronic coherence as well as electronic population trapping in the excited state when the molecular vibrations detune the system with respect to the applied field. The method offers a practical way to use on-the-fly dynamics for modeling light-molecule interactions that lead to interesting photochemical events.

  14. Mean field ring polymer molecular dynamics for electronically nonadiabatic reaction rates.

    Science.gov (United States)

    Duke, Jessica Ryan; Ananth, Nandini

    2016-12-22

    We present a mean field ring polymer molecular dynamics method to calculate the rate of electron transfer (ET) in multi-state, multi-electron condensed-phase processes. Our approach involves calculating a transition state theory (TST) estimate to the rate using an exact path integral in discrete electronic states and continuous Cartesian nuclear coordinates. A dynamic recrossing correction to the TST rate is then obtained from real-time dynamics simulations using mean field ring polymer molecular dynamics. We employ two different reaction coordinates in our simulations and show that, despite the use of mean field dynamics, the use of an accurate dividing surface to compute TST rates allows us to achieve remarkable agreement with Fermi's golden rule rates for nonadiabatic ET in the normal regime of Marcus theory. Further, we show that using a reaction coordinate based on electronic state populations allows us to capture the turnover in rates for ET in the Marcus inverted regime.

  15. Implementation of sorption hysteresis in multi-Fickian moisture transport

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Svensson, Staffan

    2007-01-01

    In the cellular structure of wood, bound-water diffusion and water-vapor diffusion interact via sorption in a complex moisture-transportation system. At low relative humidity, moisture transport may be modeled by a Fickian diffusion equation to a good approximation. At higher relative humidity...... this behavior. The multi-Fickian model describes the combined transport of bound water and vapor and their interaction through sorption. The bound-water concentration is also influenced by sorption hysteresis. In the worst case, sorption hysteresis may result in deviations of up to 30-35% in moisture content....... Hence, for a precise moisture content computation, sorption hysteresis must be taken into account. The present paper explains the relation between sorption hysteresis and multi-Fickian moisture transport, and clarifies how models for the two phenomena are coupled. To illustrate the effects, a finite...

  16. Organic fields sustain weed metacommunity dynamics in farmland landscapes.

    Science.gov (United States)

    Henckel, Laura; Börger, Luca; Meiss, Helmut; Gaba, Sabrina; Bretagnolle, Vincent

    2015-06-07

    Agro-ecosystems constitute essential habitat for many organisms. Agricultural intensification, however, has caused a strong decline of farmland biodiversity. Organic farming (OF) is often presented as a more biodiversity-friendly practice, but the generality of the beneficial effects of OF is debated as the effects appear often species- and context-dependent, and current research has highlighted the need to quantify the relative effects of local- and landscape-scale management on farmland biodiversity. Yet very few studies have investigated the landscape-level effects of OF; that is to say, how the biodiversity of a field is affected by the presence or density of organically farmed fields in the surrounding landscape. We addressed this issue using the metacommunity framework, with weed species richness in winter wheat within an intensively farmed landscape in France as model system. Controlling for the effects of local and landscape structure, we showed that OF leads to higher local weed diversity and that the presence of OF in the landscape is associated with higher local weed biodiversity also for conventionally farmed fields, and may reach a similar biodiversity level to organic fields in field margins. Based on these results, we derive indications for improving the sustainable management of farming systems. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

  17. Organic fields sustain weed metacommunity dynamics in farmland landscapes

    Science.gov (United States)

    Henckel, Laura; Börger, Luca; Meiss, Helmut; Gaba, Sabrina; Bretagnolle, Vincent

    2015-01-01

    Agro-ecosystems constitute essential habitat for many organisms. Agricultural intensification, however, has caused a strong decline of farmland biodiversity. Organic farming (OF) is often presented as a more biodiversity-friendly practice, but the generality of the beneficial effects of OF is debated as the effects appear often species- and context-dependent, and current research has highlighted the need to quantify the relative effects of local- and landscape-scale management on farmland biodiversity. Yet very few studies have investigated the landscape-level effects of OF; that is to say, how the biodiversity of a field is affected by the presence or density of organically farmed fields in the surrounding landscape. We addressed this issue using the metacommunity framework, with weed species richness in winter wheat within an intensively farmed landscape in France as model system. Controlling for the effects of local and landscape structure, we showed that OF leads to higher local weed diversity and that the presence of OF in the landscape is associated with higher local weed biodiversity also for conventionally farmed fields, and may reach a similar biodiversity level to organic fields in field margins. Based on these results, we derive indications for improving the sustainable management of farming systems. PMID:25994672

  18. Dynamically broken gauge model without fundamental scalar fields

    Energy Technology Data Exchange (ETDEWEB)

    Snyderman, N. J.; Guralnik, G. S.

    1976-01-01

    It is shown that the structure that must be generated by dynamical symmetry breaking solutions to gauge theories can be explicitly implemented with a 4-fermion interaction. This structure arises in order to obtain consistency with the constraints imposed by a Goldstone commutator proportional to (anti psi psi). One demonstrates these ideas within the context of axial electrodynamics, dynamically breaking chiral symmetry. As a pre-requisite it is shown how the Nambu-Jona-Lasinio model becomes renormalizable with respect to a systematic approximation scheme that respects the Goldstone commutator of dynamically broken chiral symmetry to each order of approximation. (This approximation scheme is equivalent to a l/N expansion, where N is set to unity at the end of the calculations). This solution generates new interactions not explicitly present in the original Lagrangian and does not have a 4-fermion contact interaction. The renormalized Green's functions are shown to correspond to those of the sigma-model, summed as though the fermions had N components, and for which lambda/sub 0/ = 2g/sub 0//sup 2/. This correspondence is exact except for the possibility that the renormalized coupling of the Nambu-Jona-Lasinio model may be a determined number.

  19. Dynamically broken gauge model without fundamental scalar fields

    International Nuclear Information System (INIS)

    Snyderman, N.J.; Guralnik, G.S.

    1976-01-01

    It is shown that the structure that must be generated by dynamical symmetry breaking solutions to gauge theories can be explicitly implemented with a 4-fermion interaction. This structure arises in order to obtain consistency with the constraints imposed by a Goldstone commutator proportional to [anti psi psi]. One demonstrates these ideas within the context of axial electrodynamics, dynamically breaking chiral symmetry. As a pre-requisite it is shown how the Nambu-Jona-Lasinio model becomes renormalizable with respect to a systematic approximation scheme that respects the Goldstone commutator of dynamically broken chiral symmetry to each order of approximation. (This approximation scheme is equivalent to a l/N expansion, where N is set to unity at the end of the calculations). This solution generates new interactions not explicitly present in the original Lagrangian and does not have a 4-fermion contact interaction. The renormalized Green's functions are shown to correspond to those of the sigma-model, summed as though the fermions had N components, and for which lambda 0 = 2g 0 2 . This correspondence is exact except for the possibility that the renormalized coupling of the Nambu-Jona-Lasinio model may be a determined number

  20. Magnetic hysteresis classification of the lunar surface and the interpretation of permanent remanence in lunar surface samples

    Science.gov (United States)

    Wasilewski, P.

    1972-01-01

    A magnetic hysteresis classification of the lunar surface is presented. It was found that there is a distinct correlation between natural remanence (NRM), saturation magnetization, and the hysteresis ratios for the rock samples. The hysteresis classification is able to explain some aspects of time dependent magnetization in the lunar samples and relates the initial susceptibility to NRM, viscous remanence, and to other aspects of magnetization in lunar samples. It is also considered that since up to 60% of the iron in the lunar soil may be super paramagnetic at 400 K, and only 10% at 100 K, the 50% which becomes ferromagnetic over the cycle has the characteristics of thermoremanence and may provide for an enhancement in measurable field on the dark side during a subsatellite magnetometer circuit.

  1. Hysteresis in the tearing mode locking/unlocking due to resonant magnetic perturbations in EXTRAP T2R

    Science.gov (United States)

    Fridström, R.; Frassinetti, L.; Brunsell, P. R.

    2015-10-01

    The physical mechanisms behind the hysteresis in the tearing mode locking and unlocking to a resonant magnetic perturbation (RMP) are experimentally studied in EXTRAP T2R reversed-field pinch. The experiments show that the electromagnetic and the viscous torque increase with increasing perturbation amplitude until the mode locks to the wall. At the wall-locking, the plasma velocity reduction profile is peaked at the radius where the RMP is resonant. Thereafter, the viscous torque drops due to the relaxation of the velocity in the central plasma. This is the main reason for the hysteresis in the RMP locking and unlocking amplitude. The increased amplitude of the locked tearing mode produces further deepening of the hysteresis. Both experimental results are in qualitative agreement with the model in Fitzpatrick et al (2001 Phys. Plasmas 8 4489)

  2. Influence of pesticide treatments on the dynamics of whiteflies and associated parasitoids in snap bean fields

    NARCIS (Netherlands)

    Manzano, M.R.; Lenteren, van J.C.; Cardona, C.

    2003-01-01

    To determine the influence of pesticide treatments on the population dynamics of the whiteflies Trialeurodes vaporariorum (Westwood) and Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and their naturally occurring parasitoids, we performed field experiments on insecticide sprayed and unsprayed

  3. Noncommutative Field Theory and the Dynamics of Quantum Hall Fluids

    CERN Document Server

    Barbón, José L F

    2002-01-01

    We study the spectrum of density fluctuations of Fractional Hall Fluids in the context of the noncommutative hidrodynamical model of Susskind. We show that, within the weak-field expansion, the leading correction to the noncommutative Chern--Simons Lagrangian (a Maxwell term in the effective action,) destroys the incompressibility of the Hall fluid due to strong UV/IR effects at one loop. We speculate on possible relations of this instability with the transition to the Wigner crystal, and conclude that calculations within the weak-field expansion must be carried out with an explicit ultraviolet cutoff at the noncommutativity scale. We point out that the noncommutative dipoles exactly match the spatial structure of the Halperin--Kallin quasiexcitons. Therefore, we propose that the noncommutative formalism must describe accurately the spectrum at very large momenta, provided no weak-field approximations are made. We further conjecture that the noncommutative open Wilson lines are `vertex operators' for the quas...

  4. Dynamics of collisional particles in a fluctuating magnetic field

    International Nuclear Information System (INIS)

    Spineanu, F.; Vlad, M.

    1995-01-01

    The equations of motion of a test particle in a stochastic magnetic field and interacting through collisions with a plasma are Langevin-type equations. Under reasonable assumptions on the statistical properties of the random processes (field and collisional velocity fluctuations), we perform an analytical calculation of the mean-square displacement (MSD) of the particle. The basic nonlinearity in the problem (Lagrangian argument of the random field) yields complicated averages, which we carry out using a functional formalism. The result is expressed as a series, and we find the conditions for its convergence, i.e. the limits of validity of our approach (essentially, we must restrict attention to non-chaotic regimes). Further, employing realistic bounds (spectral cut-off and limited time of observation), we derive an explicit formula for the MSD. We show that from this unique expression, we can obtain several previously known results. (author)

  5. Multiple ionization dynamics of molecules in intense laser fields

    International Nuclear Information System (INIS)

    Ichimura, Atsushi; Ohyama-Yamaguchi, Tomoko

    2005-01-01

    A classical field-ionization model is developed for sequential multiple ionization of diatomic and linear triatomic molecules exposed to intense (∼ 10 15 W/cm 2 ) laser fields. The distance R ion of Coulomb explosion is calculated for a combination of fragment charges, by considering nonadiabatic excitation followed by field ionization associated with the inner and outer saddle points. For diatomic molecules (N 2 , NO, and I 2 ), the model explains behaviors observed in experiments, as R ion (21→31) ion (21→22) between competing charge-asymmetric and symmetric channels, and even-odd fluctuation along a principal pathway. For a triatomic molecule CO 2 , a comparison of the model with an experiment suggests that charge-symmetric (or nearly symmetric) channels are dominantly populated. (author)

  6. Reduction of Dynamic Field Errors in Superconductive Undulators

    CERN Document Server

    Peiffer, Peter; Burkart, Florian; Ehlers, Sandra; Keilmann, Alexander; Baumbach, Tilo; Rossmanith, Robert; Schoerling, Daniel

    2010-01-01

    The magnetic field in superconductive undulators is changed by varying the current in the superconductive wires. During operation at stable current, the electric current is confined to the resistance-free filaments. During ramping, however, the superconducting wire bundles have an inductive impedance, causing part of the current to penetrate into the iron body if electric insulation leaks between the wire and the iron body are present. If this is the case the leak currents and other eddy currents decay slowly after the ramp. The magnetic field of the undulator changes during this period. It was shown experimentally that an effective electric insulation between the wires and the iron body can minimize the current and the magnetic field drifts. In this paper the results of these experiments and simulations of the described effects are presented

  7. Does a dynamic chair increase office workers' movements? - Results from a combined laboratory and field study.

    Science.gov (United States)

    Grooten, Wilhelmus J A; Äng, Björn O; Hagströmer, Maria; Conradsson, David; Nero, Håkan; Franzén, Erika

    2017-04-01

    Dynamic chairs have the potential to facilitate movements that could counteract health problems associated with sedentary office work. This study aimed to evaluate whether a dynamic chair can increase movements during desk-based office work. Fifteen healthy subjects performed desk-based office work using a dynamic office chair and compared to three other conditions in a movement laboratory. In a field study, the dynamic office chair was studied during three working days using accelerometry. Equivocal results showed that the dynamic chair increased upper body and chair movements as compared to the conventional chair, but lesser movements were found compared to standing. No differences were found between the conditions in the field study. A dynamic chair may facilitate movements in static desk-based office tasks, but the results were not consistent for all outcome measures. Validation of measuring protocols for assessing movements during desk-based office work is warranted. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Minor hysteresis loops measurements for characterization of cast iron

    Czech Academy of Sciences Publication Activity Database

    Vértesy, G.; Uchimoto, T.; Takagi, T.; Tomáš, Ivan; Stupakov, Oleksandr; Mészáros, I.; Pávó, J.

    2006-01-01

    Roč. 372, - (2006), s. 156-159 ISSN 0921-4526. [International Symposium on Hysteresis and Micromagnetic modeling /5./. Budapest, 30.05.2005-01.06.2005] R&D Projects: GA AV ČR(CZ) 1QS100100508 Institutional research plan: CEZ:AV0Z10100520 Keywords : hysteresis-magnetic * non-destruktive testing * ferromagnetic material * magnetization curves Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.872, year: 2006

  9. Electric Potential and Electric Field Imaging with Dynamic Applications & Extensions

    Science.gov (United States)

    Generazio, Ed

    2017-01-01

    The technology and methods for remote quantitative imaging of electrostatic potentials and electrostatic fields in and around objects and in free space is presented. Electric field imaging (EFI) technology may be applied to characterize intrinsic or existing electric potentials and electric fields, or an externally generated electrostatic field made be used for volumes to be inspected with EFI. The baseline sensor technology (e-Sensor) and its construction, optional electric field generation (quasi-static generator), and current e- Sensor enhancements (ephemeral e-Sensor) are discussed. Critical design elements of current linear and real-time two-dimensional (2D) measurement systems are highlighted, and the development of a three dimensional (3D) EFI system is presented. Demonstrations for structural, electronic, human, and memory applications are shown. Recent work demonstrates that phonons may be used to create and annihilate electric dipoles within structures. Phonon induced dipoles are ephemeral and their polarization, strength, and location may be quantitatively characterized by EFI providing a new subsurface Phonon-EFI imaging technology. Results from real-time imaging of combustion and ion flow, and their measurement complications, will be discussed. Extensions to environment, Space and subterranean applications will be presented, and initial results for quantitative characterizing material properties are shown. A wearable EFI system has been developed by using fundamental EFI concepts. These new EFI capabilities are demonstrated to characterize electric charge distribution creating a new field of study embracing areas of interest including electrostatic discharge (ESD) mitigation, manufacturing quality control, crime scene forensics, design and materials selection for advanced sensors, combustion science, on-orbit space potential, container inspection, remote characterization of electronic circuits and level of activation, dielectric morphology of

  10. Decoherence and dynamical entropy generation in quantum field theory

    Energy Technology Data Exchange (ETDEWEB)

    Koksma, Jurjen F., E-mail: J.F.Koksma@uu.nl [Institute for Theoretical Physics (ITP) and Spinoza Institute, Utrecht University, Postbus 80195, 3508 TD Utrecht (Netherlands); Prokopec, Tomislav, E-mail: T.Prokopec@uu.nl [Institute for Theoretical Physics (ITP) and Spinoza Institute, Utrecht University, Postbus 80195, 3508 TD Utrecht (Netherlands); Schmidt, Michael G., E-mail: M.G.Schmidt@thphys.uni-heidelberg.de [Institut fuer Theoretische Physik, Heidelberg University, Philosophenweg 16, D-69120 Heidelberg (Germany)

    2012-01-20

    We formulate a novel approach to decoherence based on neglecting observationally inaccessible correlators. We apply our formalism to a renormalised interacting quantum field theoretical model. Using out-of-equilibrium field theory techniques we show that the Gaussian von Neumann entropy for a pure quantum state increases to the interacting thermal entropy. This quantifies decoherence and thus measures how classical our pure state has become. The decoherence rate is equal to the single particle decay rate in our model. We also compare our approach to existing approaches to decoherence in a simple quantum mechanical model. We show that the entropy following from the perturbative master equation suffers from physically unacceptable secular growth.

  11. Mean field dynamics and color conductivity of cold and dense quark matter

    International Nuclear Information System (INIS)

    Zhang Chao; Zheng Xiaoping

    2002-01-01

    The authors first review the non-Abelian transport theory and its mean field dynamics. The theory is then applied for studying the color electric dynamics of cold and dense quark matter at large chemical potential, and color conductivity with non-perturbation effect is obtained. Finally, the authors compare the results at large chemical potential with that at high temperature, and discuss possible applications in the field of astrophysics

  12. Controlling the dynamics of a self-organized structure using a rf-field

    International Nuclear Information System (INIS)

    Talasman, S.J.; Ignat, M.

    2004-01-01

    We investigate the influence of an external rf-field upon a plasma self-organized structure. We show that depending on the intensity of this field, though it is at very low values, the dynamics of the structure can be easily controlled over a wide range of the state parameters values. This could be considered as a non-feedback method of dynamics control

  13. Numerical study of self-field effects on dynamics of Josephson-junction arrays

    International Nuclear Information System (INIS)

    Phillips, J.R.; Van der Zant, H.S.J.; White, J.; Orlando, T.P.

    1994-01-01

    We consider the influence of self-induced magnetic fields on dynamic properties of arrays of resistively and capacitively shunted Josephson junctions. Self-field effects are modeled by including mutual inductance interactions between every cell in the array. We find that it is important to include all mutual inductance interactions in order to understand the dynamic properties of the array, in particular subharmonic structure arising under AC current bias. (orig.)

  14. Frequency-dependent dynamic magnetic properties of the Ising bilayer system consisting of spin-3/2 and spin-5/2 spins

    Science.gov (United States)

    Keskin, Mustafa; Ertaş, Mehmet

    2018-04-01

    Dynamic magnetic properties of the Ising bilayer system consisting of the mixed (3/2, 5/2) Ising spins with a crystal-field interaction in an oscillating field on a two-layer square lattice is studied by the use of dynamic mean-field theory based on the Glauber-type stochastic. Dynamic phase transition temperatures are obtained and dynamic phase diagrams are presented in three different planes. The frequency dependence of dynamic hysteresis loops is also investigated in detail. We compare the results with some available theoretical and experimental works and observe a quantitatively good agreement with some theoretical and experimental results.

  15. Multipolar Force Fields and Their Effects on Solvent Dynamics around Simple Solutes

    DEFF Research Database (Denmark)

    Jakobsen, Sofie; Bereau, Tristan; Meuwly, Markus

    2015-01-01

    The performance of multipole (MTP) and point charge (PC) force fields in classical molecular dynamics (MD) simulations of condensed-phase systems for both equilibrium and dynamical quantities is compared. MTP electrostatics provides an improved description of the anisotropic electrostatic potential...

  16. Dynamic of Ising model with transverse field for two coupled sublattices in disordered phase

    International Nuclear Information System (INIS)

    Sa Motta, C.E.H. de.

    1984-02-01

    The dynamics of the two coupled sublattices tridimensional Ising model in a transverse field was studied by means of a continued fraction expansion for coupled operators. The static Correlation Functions necessary for studying the dynamics were calculated with the Green's Functions Method in the Random Phase Approximation (RPA). The spectral function was calculated in the region T c → . (Author) [pt

  17. Modeling hysteresis curves of anisotropic SmCoFeCuZr magnets

    Energy Technology Data Exchange (ETDEWEB)

    Sampaio da Silva, Fernanda A. [Programa de Pos-Graduacao em Engenharia Metalurgica-PUVR, Universidade Federal Fluminense, Av dos Trabalhadores 420, 27255-125 Volta Redonda, RJ (Brazil); Castro, Nicolau A. [Instituto de Pesquisas Tecnologicas, Sao Paulo, SP (Brazil); Campos, Marcos F. de, E-mail: mcampos@metal.eeimvr.uff.br [Programa de Pos-Graduacao em Engenharia Metalurgica-PUVR, Universidade Federal Fluminense, Av dos Trabalhadores 420, 27255-125 Volta Redonda, RJ (Brazil)

    2013-02-15

    The hysteresis curves at room temperature and at 630 K of an anisotropic magnet were successfully modeled with the Stoner-Wohlfarth Callen-Liu-Cullen (SW-CLC) model. This implies that coherent rotation of domains is the reversal mechanism in this magnet. The chemical composition of the evaluated magnet is Sm(Co{sub bal}Fe{sub 0.06}Cu{sub 0.108}Zr{sub 0.03}){sub 7.2}. The anisotropy field H{sub A} was estimated with the model, resulting {mu}{sub 0}H{sub A}=7.1 T at the room temperature, and 2.9 T at 630 K. For this sample, the CLC interaction parameter (1/d) is very low (near zero) and, thus, the nanocrystalline 2:17 grains are well 'magnetically decoupled'. The texture analysis using Schulz Pole figure data indicated M{sub r}/M{sub s} ratio=0.96, and this means that the magnet is very well aligned. The excellent alignment of the grains is one of the reasons for the high coercivity of this sample ({approx}4 T at room temperature). - Highlights: Black-Right-Pointing-Pointer The Stoner-Wohlfarth model can describe the hysteresis curves of anisotropic Sm2Co17 magnets, since the Callen-Liu-Cullen correction is applied. Black-Right-Pointing-Pointer The anisotropy field of the hard magnetic phase Sm2Co17 can be estimated from the hysteresis curves of anisotropic magnets, since the crystallographic texture is known. Black-Right-Pointing-Pointer It is presented a texture study of commercial sintered Sm2Co17 type magnets. Black-Right-Pointing-Pointer The texture data can be used for evaluation of the squareness of the 2nd quadrant of the hysteresis curve, in Sm2Co17 hard coercivity magnets.

  18. Dynamics of coupled field solitons: A collective coordinate approach

    Indian Academy of Sciences (India)

    In this paper we consider a class of systems of two coupled real scalar fields in bidimensional space-time, with the main motivation of studying classical stability of soliton solutions using collective coordinate approach. First, we present the class of systems of the collective coordinate equations which are derived using the ...

  19. Electric field driven fractal growth dynamics in polymeric medium

    Science.gov (United States)

    Dawar, Anit; Chandra, Amita

    2014-08-01

    This paper reports the extension of earlier work (Dawar and Chandra, 2012) [27] by including the influence of low values of electric field on diffusion limited aggregation (DLA) patterns in polymer electrolyte composites. Subsequently, specified cut-off value of voltage has been determined. Below the cut-off voltage, the growth becomes direction independent (i.e., random) and gives rise to ramified DLA patterns while above the cut-off, growth is governed by diffusion, convection and migration. These three terms (i.e., diffusion, convection and migration) lead to structural transition that varies from dense branched morphology (DBM) to chain-like growth to dendritic growth, i.e., from high field region (A) to constant field region (B) to low field region (C), respectively. The paper further explores the growth under different kinds of electrode geometries (circular and square electrode geometry). A qualitative explanation for fractal growth phenomena at applied voltage based on Nernst-Planck equation has been proposed.

  20. Vegetational dynamics in some tropical abandoned rice fields in the ...

    African Journals Online (AJOL)

    However, poor farmers of tropics being unable to adopt such soil management strategy abandon the agricultural systems because of decline in production and leave the fields to remain fallow. The present study examined the vegetational succession and quantitative community characteristics in some abandoned ...

  1. Vegetational dynamics in some tropical abandoned rice fields in the ...

    African Journals Online (AJOL)

    USER

    Ceaselpinaceae. Butea monosperma. Desmodium levigatum. Crotolaria albida. Cassia tora. 3.39. 6.15. 4.77. 14.91. Table 3. Species richness, diversity and Dominant indices of different vegetation on different abandoned rice field. Status of studied plots with respect to abandonment. Species richness. Species diversity Ĥ.

  2. [Dynamics of biomacromolecules in coherent electromagnetic radiation field].

    Science.gov (United States)

    Leshcheniuk, N S; Apanasevich, E E; Tereshenkov, V I

    2014-01-01

    It is shown that induced oscillations and periodic displacements of the equilibrium positions occur in biomacromolecules in the absence of electromagnetic radiation absorption, due to modulation of interaction potential between atoms and groups of atoms forming the non-valence bonds in macromolecules by the external electromagnetic field. Such "hyperoscillation" state causes inevitably the changes in biochemical properties of macromolecules and conformational transformation times.

  3. Field-dependent dynamic responses from dilute magnetic nanoparticle dispersions

    DEFF Research Database (Denmark)

    Fock, Jeppe; Balceris, Christoph; Costo, Rocio

    2017-01-01

    The response of magnetic nanoparticles (MNPs) to an oscillating magnetic field outside the linear response region is important for several applications including magnetic hyperthermia, magnetic resonance imaging and biodetection. The size and magnetic moment are two critical parameters for the pe...

  4. Dynamics of coupled field solitons: A collective coordinate approach

    Indian Academy of Sciences (India)

    mensional space-time, with the main motivation of studying classical stability of soliton solutions using collective coordinate ... presented in some previous works [1,2] which where motivated by investigations intro- duced in [3,4], ... The collision of coupled field solitons leads to resonance structure depending on the energy ...

  5. Quantum mean-field theory of collective dynamics and tunneling

    International Nuclear Information System (INIS)

    Negele, J.W.; Massachusetts Inst. of Tech., Cambridge

    1981-01-01

    In collaboration with Shimon Levit and Zvi Paltiel, significant progress has been made recently in formulating the quantum many-body problem in terms of an expansion about solutions to time-dependent mean-field equations. The essential ideas, principal results, and illustrative examples will be summarized here. (orig./HSI)

  6. Electron-Cloud Pinch Dynamics in Presence of Lattice Magnet Fields

    CERN Document Server

    Franchetti, G

    2011-01-01

    The pinch of the electron cloud due to a passing proton bunch was extensively studied in a field free region and in a dipolar magnetic field. For the latter study, a strong field approximation helped to formulate the equations of motion and to understand the complex electron pinch dynamics, which exhibited some similarities with the field-free situation. Here we extend the analysis to the case of electron pinch in quadrupoles and in sextupoles. We discuss the limits of validity for the strong field approximation and we evaluate the relative magnitude of the peak tune shift along the bunch expected for the different fields.

  7. Dynamic nuclear magnetic resonance field sensing with part-per-trillion resolution.

    Science.gov (United States)

    Gross, Simon; Barmet, Christoph; Dietrich, Benjamin E; Brunner, David O; Schmid, Thomas; Pruessmann, Klaas P

    2016-12-02

    High-field magnets of up to tens of teslas in strength advance applications in physics, chemistry and the life sciences. However, progress in generating such high fields has not been matched by corresponding advances in magnetic field measurement. Based mostly on nuclear magnetic resonance, dynamic high-field magnetometry is currently limited to resolutions in the nanotesla range. Here we report a concerted approach involving tailored materials, magnetostatics and detection electronics to enhance the resolution of nuclear magnetic resonance sensing by three orders of magnitude. The relative sensitivity thus achieved amounts to 1 part per trillion (10 -12 ). To exemplify this capability we demonstrate the direct detection and relaxometry of nuclear polarization and real-time recording of dynamic susceptibility effects related to human heart function. Enhanced high-field magnetometry will generally permit a fresh look at magnetic phenomena that scale with field strength. It also promises to facilitate the development and operation of high-field magnets.

  8. Spin-lattice dynamics simulation of external field effect on magnetic order of ferromagnetic iron

    International Nuclear Information System (INIS)

    Chui, C. P.; Zhou, Yan

    2014-01-01

    Modeling of field-induced magnetization in ferromagnetic materials has been an active topic in the last dozen years, yet a dynamic treatment of distance-dependent exchange integral has been lacking. In view of that, we employ spin-lattice dynamics (SLD) simulations to study the external field effect on magnetic order of ferromagnetic iron. Our results show that an external field can increase the inflection point of the temperature. Also the model provides a better description of the effect of spin correlation in response to an external field than the mean-field theory. An external field has a more prominent effect on the long range magnetic order than on the short range counterpart. Furthermore, an external field allows the magnon dispersion curves and the uniform precession modes to exhibit magnetic order variation from their temperature dependence

  9. Cometary dust dynamics and polarization in electromagnetic radiation fields

    Science.gov (United States)

    Herranen, J.; Markkanen, J.; Muinonen, K.

    2017-09-01

    In our work, we apply a fast solution of electromagnetic scattering to determine the induced spin and movement of a dust particle in a cometary coma. The resulted aligned spinning state is then used to determine the observable polarization of the dust, and compared against the randomly averaged polarization of the same particle. We find that measurable effects arise due to the alignment. In the future, similar methods can be used to model the dynamics and in turn the polarization of the whole coma.

  10. Gesture Recognition using Latent-Dynamic based Conditional Random Fields and Scalar Features

    Science.gov (United States)

    Yulita, I. N.; Fanany, M. I.; Arymurthy, A. M.

    2017-02-01

    The need for segmentation and labeling of sequence data appears in several fields. The use of the conditional models such as Conditional Random Fields is widely used to solve this problem. In the pattern recognition, Conditional Random Fields specify the possibilities of a sequence label. This method constructs its full label sequence to be a probabilistic graphical model based on its observation. However, Conditional Random Fields can not capture the internal structure so that Latent-based Dynamic Conditional Random Fields is developed without leaving external dynamics of inter-label. This study proposes the use of Latent-Dynamic Conditional Random Fields for Gesture Recognition and comparison between both methods. Besides, this study also proposes the use of a scalar features to gesture recognition. The results show that performance of Latent-dynamic based Conditional Random Fields is not better than the Conditional Random Fields, and scalar features are effective for both methods are in gesture recognition. Therefore, it recommends implementing Conditional Random Fields and scalar features in gesture recognition for better performance

  11. Dynamical hysteresis and spatial synchronization in coupled non ...

    Indian Academy of Sciences (India)

    uniform phase evolution and chaotic amplitude) models, etc. [12] L D Iasemidis, A Prasad, J C Sackellares, P M Pardalos and D-S Shiau, in Order and chaos edited by T Bountis and S Pneumatikos (Publishing House of K Sfakianakis,. Thessaloniki ...

  12. Dynamically assisted Sauter-Schwinger effect in inhomogeneous electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Christian; Schützhold, Ralf [Fakultät für Physik, Universität Duisburg-Essen,Lotharstrasse 1, 47057 Duisburg (Germany)

    2016-02-24

    Via the world-line instanton method, we study electron-positron pair creation by a strong (but sub-critical) electric field of the profile E/cosh{sup 2} (kx) superimposed by a weaker pulse E{sup ′}/cosh{sup 2} (ωt). If the temporal Keldysh parameter γ{sub ω}=mω/(qE) exceeds a threshold value γ{sub ω}{sup crit} which depends on the spatial Keldysh parameter γ{sub k}=mk/(qE), we find a drastic enhancement of the pair creation probability — reporting on what we believe to be the first analytic non-perturbative result for the interplay between temporal and spatial field dependences E(t,x) in the Sauter-Schwinger effect. Finally, we speculate whether an analogous effect (drastic enhancement of tunneling probability) could occur in other scenarios such as stimulated nuclear decay, for example.

  13. Field driven charging dynamics of a fluidized granular bed.

    Science.gov (United States)

    Yoshimatsu, R; Araújo, N A M; Shinbrot, T; Herrmann, H J

    2016-07-20

    A simplified model has previously described the inductive charging of colliding identical grains in the presence of an external electric field. Here we extend that model by including heterogeneous surface charge distributions, grain rotations and electrostatic interactions between grains. We find from this more realistic model that strong heterogeneities in charging can occur in agitated granular beds, and we predict that shielding due to these heterogeneities can dramatically alter the charging rate in such beds.

  14. Field Driven Charging Dynamics of a Fluidized Granular Bed

    OpenAIRE

    Yoshimatsu, R.; Araújo, N. A. M.; Shinbrot, T.; Herrmann, H. J.

    2016-01-01

    A simplified model has previously described the inductive charging of colliding identical grains in the presence of an external electric field. Here we extend that model by including heterogeneous surface charge distributions, grain rotations and electrostatic interactions between grains. We find from this more realistic model that strong heterogeneities in charging can occur in agitated granular beds, and we predict that shielding due to these heterogeneities can dramatically alter the charg...

  15. Self-field effects on electron dynamics in free-electron lasers with axial magnetic field

    International Nuclear Information System (INIS)

    Mirzanejhad, S.; Maraghechi, B.; Mohsenpour, T.

    2004-01-01

    A self-consistent method for the analysis of self-magnetic field for a free-electron laser with a one-dimensional helical wiggler and an axial guide magnetic field is presented. The equilibrium orbits and their stability, under the influence of self-electric and self-magnetic fields, are analyzed. New unstable orbits, in the first part of the Group I orbits and in the resonance region of the Group II orbits, are found. It is shown that an increase in the defocusing effect of self-fields will widen the unstable orbits. An anomalous self-field regime is found where an increase in the defocusing effect of self-fields can have stabilizing effect on the resonance region

  16. Dynamics of Charged Particles and their Radiation Field

    International Nuclear Information System (INIS)

    Poisson, E

    2006-01-01

    The motion of a charged particle interacting with its own electromagnetic field is an area of research that has a long history. On the one hand the theory ought to be straightforward to formulate: one has Maxwell's equations that tell the field how to behave and one has the Lorentz-force law that tells the particle how to move (given the field). On the other hand the theory is fundamentally ambiguous because of the field singularities that necessarily come with a point particle. While each separate sub-problem can easily be solved, to couple the field to the particle in a self-consistent treatment turns out to be tricky. I believe it is this dilemma that has been the main source of the endless fascination. For them it is also rooted in the fact that the electromagnetic self-force problem is deeply analogous to the gravitational self-force problem, which is of direct relevance to future gravitational wave observations. The motion of point particles in curved spacetime has been the topic of a recent Topical Review, and it was the focus of a recent Special Issue. Exceptions are Rohrlich's excellent text, which makes a very useful introduction to radiation reaction, and the Landau and Lifshitz classic, which contains what is probably the most perfect summary of the foundational ideas. It is therefore with some trepidation that I received Herbert Spohn's book, which covers both the classical and quantum theories of a charged particle coupled to its own field (the presentation is limited to flat spacetime). Is this the text that graduate students and researchers should turn to in order to get a complete and accessible education in radiation reaction? My answer is that while the book does indeed contain a lot of useful material, it is not a very accessible source of information, and it is certainly not a student-friendly textbook. Instead, the book presents a technical account of the author's personal take on the theory, and represents a culminating summary of the author

  17. Auxiliary fields in the geometrical relativistic particle dynamics

    International Nuclear Information System (INIS)

    Amador, A; Bagatella, N; Rojas, E; Cordero, R

    2008-01-01

    We describe how to construct the dynamics of relativistic particles, following either timelike or null curves, by means of an auxiliary variables method instead of the standard theory of deformations for curves. There are interesting physical particle models governed by actions that involve higher order derivatives of the embedding functions of the worldline. We point out that the mechanical content of such models can be extracted wisely from a lower order action, which can be performed by implementing in the action a finite number of constraints that involve the geometrical relationship structures inherent to a curve and by using a covariant formalism. We emphasize our approach for null curves. For such systems, the natural time parameter is a pseudo-arclength whose properties resemble those of the standard proper time. We illustrate the formalism by applying it to some models for relativistic particles

  18. Auxiliary fields in the geometrical relativistic particle dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Amador, A; Bagatella, N; Rojas, E [Departamento de Fisica, Facultad de Fisica e Inteligencia Artificial, Universidad Veracruzana, 91000 Xalapa, Veracruz (Mexico); Cordero, R [Departamento de Fisica, Escuela Superior de Fisica y Matematicas del I.P.N, Edificio 9, 07738 Mexico D.F (Mexico)], E-mail: aramador@gmail.com, E-mail: nbagatella@uv.mx, E-mail: cordero@esfm.ipn.mx, E-mail: efrojas@uv.mx

    2008-03-21

    We describe how to construct the dynamics of relativistic particles, following either timelike or null curves, by means of an auxiliary variables method instead of the standard theory of deformations for curves. There are interesting physical particle models governed by actions that involve higher order derivatives of the embedding functions of the worldline. We point out that the mechanical content of such models can be extracted wisely from a lower order action, which can be performed by implementing in the action a finite number of constraints that involve the geometrical relationship structures inherent to a curve and by using a covariant formalism. We emphasize our approach for null curves. For such systems, the natural time parameter is a pseudo-arclength whose properties resemble those of the standard proper time. We illustrate the formalism by applying it to some models for relativistic particles.

  19. The linear σ-ω model in the thermo field dynamics

    International Nuclear Information System (INIS)

    Aguirre, R.; Civitarese, O.; De Paoli, A.L.

    1994-01-01

    The relativistic linear σ-ω model is used to describe symmetric nuclear matter at finite temperature. The thermo field dynamics is applied to compute, perturbatively, quantum corrections to the temperature-dependent Hartree mean field. The effect of these corrections upon nuclear-matter properties at saturation is studied. ((orig.))

  20. Dynamical response of the Ising model to the time dependent magnetic field with white noise

    Science.gov (United States)

    Akıncı, Ümit

    2018-03-01

    The effect of the white noise in time dependent magnetic field on the dynamic behavior of the Ising model has been investigated within the effective field theory based on Glauber type of stochastic process. Discrete white noise has been chosen from both Gaussian and uniform probability distributions. Detailed investigation on probability distribution of dynamical order parameter results that, both type of noise distributions yield the same probability distribution related to the dynamical order parameter, namely Gaussian probability distribution. The variation of the parameters that describe the probability distribution of dynamical order parameter (mean value and standard deviation) with temperature and strength of the noise have been inspected. Also, it has been shown that, rising strength of the noise can induce dynamical phase transition in the system.

  1. Chaotic dynamics and basin erosion in nanomagnets subject to time-harmonic magnetic fields

    Energy Technology Data Exchange (ETDEWEB)

    D' Aquino, M., E-mail: daquino@uniparthenope.it [Engineering Department, University of Naples “Parthenope”, 80143 Naples (Italy); Quercia, A.; Serpico, C. [DIETI, University of Naples Federico II, 80125 Naples (Italy); Bertotti, G. [Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Mayergoyz, I.D. [ECE Department and UMIACS, University of Maryland, College Park, MD 20742 (United States); Perna, S. [DIETI, University of Naples Federico II, 80125 Naples (Italy); Ansalone, P. [Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy)

    2016-04-01

    Magnetization dynamics in uniformly magnetized particles subject to time-harmonic (AC) external fields is considered. The study is focused on the behavior of the AC-driven dynamics close to saddle equilibria. It happens that such dynamics has chaotic nature at moderately low power level, due to the heteroclinic tangle phenomenon which is produced by the combined effect of AC-excitations and saddle type dynamics. By using analytical theory for the threshold AC excitation amplitudes necessary to create the heteroclinic tangle together with numerical simulations, we quantify and show how the tangle produces the erosion of the safe basin around the stable equilibria.

  2. Dynamics of Coulomb correlations in semiconductors in high magnetic fields

    International Nuclear Information System (INIS)

    Fromer, Neil Alan

    2002-01-01

    Current theories have been successful in explaining many nonlinear optical experiments in undoped semiconductors. However, these theories require a ground state which is assumed to be uncorrelated. Strongly correlated systems of current interest, such as a two dimensional electron gas in a high magnetic field, cannot be explained in this manner because the correlations in the ground state and the low energy collective excitations cause a breakdown of the conventional techniques. We perform ultrafast time-resolved four-wave mixing on $n$-modulation doped quantum wells, which contain a quasi-two dimensional electron gas, in a large magnetic field, when only a single Landau level is excited and also when two levels are excited together. We find evidence for memory effects and as strong coupling between the Landau levels induced by the electron gas. We compare our results with simulations based on a new microscopic approach capable of treating the collective effects and correlations of the doped electrons, and find a good qualitative agreement. By looking at the individual contributions to the model, we determine that the unusual correlation effects seen in the experiments are caused by the scattering of photo-excited electron-hole pairs with the electron gas, leading to new excited states which are not present in undoped semiconductors, and also by exciton-exciton interactions mediated by the long-lived collective excitations of the electron gas, inter-Landau level magnetoplasmons

  3. Primordial gravitational waves from axion-gauge fields dynamics

    International Nuclear Information System (INIS)

    Dimastrogiovanni, Emanuela; Fasiello, Matteo; Fujita, Tomohiro

    2017-01-01

    Inspired by the chromo-natural inflation model of Adshead and Wyman, we reshape its scalar content to relax the tension with current observational bounds. Besides an inflaton, the setup includes a spectator sector in which an axion and SU(2) gauge fields are coupled via a Chern-Simons-type term. The result is a viable theory endowed with an alternative production mechanism for gravitational waves during inflation. The gravitational wave signal sourced by the spectator fields can be much larger than the contribution from standard vacuum fluctuations, it is distinguishable from the latter on the basis of its chirality and, depending on the theory parameters values, also its tilt. This production process breaks the well-known relation between the tensor-to-scalar ratio and the energy scale of inflation. As a result, even if the Hubble rate is itself too small for the vacuum to generate a tensor amplitude detectable by upcoming experiments, this model still supports observable gravitational waves.

  4. On unified field theories, dynamical torsion and geometrical models: II

    International Nuclear Information System (INIS)

    Cirilo-Lombardo, D.J.

    2011-01-01

    We analyze in this letter the same space-time structure as that presented in our previous reference (Part. Nucl, Lett. 2010. V.7, No.5. P.299-307), but relaxing now the condition a priori of the existence of a potential for the torsion. We show through exact cosmological solutions from this model, where the geometry is Euclidean RxO 3 ∼ RxSU(2), the relation between the space-time geometry and the structure of the gauge group. Precisely this relation is directly connected with the relation of the spin and torsion fields. The solution of this model is explicitly compared with our previous ones and we find that: i) the torsion is not identified directly with the Yang-Mills type strength field, ii) there exists a compatibility condition connected with the identification of the gauge group with the geometric structure of the space-time: this fact leads to the identification between derivatives of the scale factor a with the components of the torsion in order to allow the Hosoya-Ogura ansatz (namely, the alignment of the isospin with the frame geometry of the space-time), and iii) of two possible structures of the torsion the 'tratorial' form (the only one studied here) forbid wormhole configurations, leading only to cosmological instanton space-time in eternal expansion

  5. Multiagent model and mean field theory of complex auction dynamics

    Science.gov (United States)

    Chen, Qinghua; Huang, Zi-Gang; Wang, Yougui; Lai, Ying-Cheng

    2015-09-01

    Recent years have witnessed a growing interest in analyzing a variety of socio-economic phenomena using methods from statistical and nonlinear physics. We study a class of complex systems arising from economics, the lowest unique bid auction (LUBA) systems, which is a recently emerged class of online auction game systems. Through analyzing large, empirical data sets of LUBA, we identify a general feature of the bid price distribution: an inverted J-shaped function with exponential decay in the large bid price region. To account for the distribution, we propose a multi-agent model in which each agent bids stochastically in the field of winner’s attractiveness, and develop a theoretical framework to obtain analytic solutions of the model based on mean field analysis. The theory produces bid-price distributions that are in excellent agreement with those from the real data. Our model and theory capture the essential features of human behaviors in the competitive environment as exemplified by LUBA, and may provide significant quantitative insights into complex socio-economic phenomena.

  6. Dynamic Vehicle Detection via the Use of Magnetic Field Sensors

    Directory of Open Access Journals (Sweden)

    Vytautas Markevicius

    2016-01-01

    Full Text Available The vehicle detection process plays the key role in determining the success of intelligent transport management system solutions. The measurement of distortions of the Earth’s magnetic field using magnetic field sensors served as the basis for designing a solution aimed at vehicle detection. In accordance with the results obtained from research into process modeling and experimentally testing all the relevant hypotheses an algorithm for vehicle detection using the state criteria was proposed. Aiming to evaluate all of the possibilities, as well as pros and cons of the use of anisotropic magnetoresistance (AMR sensors in the transport flow control process, we have performed a series of experiments with various vehicles (or different series from several car manufacturers. A comparison of 12 selected methods, based on either the process of determining the peak signal values and their concurrence in time whilst calculating the delay, or by measuring the cross-correlation of these signals, was carried out. It was established that the relative error can be minimized via the Z component cross-correlation and Kz criterion cross-correlation methods. The average relative error of vehicle speed determination in the best case did not exceed 1.5% when the distance between sensors was set to 2 m.

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

    Directory of Open Access Journals (Sweden)

    Jhih-Hong Lin

    2015-04-01

    Full Text Available 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.

  8. Hysteresis loops of spin-dependent electronic current in a paramagnetic resonant tunnelling diode

    International Nuclear Information System (INIS)

    Wójcik, P; Spisak, B J; Wołoszyn, M; Adamowski, J

    2012-01-01

    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. (paper)

  9. Mechanisms for Hysteresis in a Horizontal Unsaturated Fracture with Matric Imbibition

    Science.gov (United States)

    Fox, D. T.; Glass, R. J.

    2002-12-01

    Within porous media, macroscopic hysteretic pressure-saturation relations have long been thought to be the result of microscopic effects such as phase invasion within local `ink bottle' geometry, phase trapping or accessibility, and differences between solid-liquid-liquid contact angles for wetting and nonwetting invasion. Here we consider the mechanisms for hysteresis within a horizontal rough-walled fracture. An analogue horizontal rough-walled fracture (10 cm x 15 cm) was formed by placing a piece of transparent textured glass against a water saturated, flat porous plate. Water could enter and leave the fracture via the porous plate while air entered or left via the fracture edges. The evolution of wetted structure within the fracture was recorded with digital images taken through the transparent side as the tension in the porous plate was raised and lowered. Following a sequence of such invasion experiments, the porous plate was replaced with a piece of flat glass and the aperture field was measured using a light transmission technique. Analysis of digital images taken during displacement demonstrated that the macroscopic hysteresis in pressure-saturation curves resulted primarily from the underlying microscopic mechanisms of ink bottle and phase trapping accessibility. Additionally, we found the wetted structure within the fracture to become connected and form a satiated (0 tension) structure containing complex entrapped air structures (volumetric saturation ~0.5) thus greatly reducing permeability at 0 tension. The pressure at which this structure formed on wetting and fragmented on drainage also showed significant hysteresis.

  10. An incremental theory of magneto-elastic hysteresis in pseudo-cubic ferro-magnetostrictive alloys

    International Nuclear Information System (INIS)

    Armstrong, W.D.

    2003-01-01

    This paper presents an incremental hysteretic magneto-elastic constitutive theory of pseudo-cubic ferro-magnetostrictive alloys, which may be used to predict the magneto-elastic response of these materials under quite general applied magnetic field and stress processes. These processes may include fully saturated major loop, unsaturated minor loop or more general types of magnetic field-stress processes. Comparisons between model results and a set of high quality measurements show that the model is capable of qualitative agreement with the experimental behavior. However, the experimental data shows a strongly decreasing magnetization and magnetostriction hysteresis as the minor loop cyclic applied field amplitude becomes smaller. It appears that irreversible domain wall motion continuously activates as the applied magnetic field is reduced in the range from 79 to 39 kA/m. Minor loop processes which do not have a sufficiently low minimum applied magnetic field value do not activate irreversible domain wall translation events and any measured magnetization changes must be due to one or more reversible mechanisms such as domain wall bowing and reversible domain rotation. The present model only includes an irreversible domain wall translation mechanism, therefore the model hysteresis widths remain constant with decreasing minor loop cyclic applied field amplitude

  11. Density nonlinearities and a field theory for the dynamics of simple fluids

    OpenAIRE

    Mazenko, Gene F.; Yeo, Joonhyun

    1994-01-01

    We study the role of the Jacobian arising from a constraint enforcing the nonlinear relation: ${\\bf g}=\\rho{\\bf V}$, where $\\rho,\\: {\\bf g}$ and ${\\bf V}$ are the mass density, the momentum density and the local velocity field, respectively, in the field theoretic formulation of the nonlinear fluctuating hydrodynamics of simple fluids. By investigating the Jacobian directly and by developing a field theoretic formulation without the constraint, we find that no changes in dynamics result as co...

  12. Analysis of Wetting and Contact Angle Hysteresis on Chemically Patterned Surfaces

    KAUST Repository

    Xu, Xianmin

    2011-01-01

    Wetting and contact angle hysteresis on chemically patterned surfaces in two dimensionsare analyzed from a stationary phase-field model for immiscible two phase fluids. We first study the sharp-interface limit of the model by the method of matched asymptotic expansions. We then justify the results rigorously by the γ-convergence theory for the related variational problem and study the properties of the limiting minimizers. The results also provide a clear geometric picture of the equilibrium configuration of the interface. This enables us to explicitly calculate the total surface energy for the two phase systems on chemically patterned surfaces with simple geometries, namely the two phase flow in a channel and the drop spreading. By considering the quasi-staticmotion of the interface described by the change of volume (or volume fraction), we can follow the change-of-energy landscape which also reveals the mechanism for the stick-slip motion of the interface and contact angle hysteresis on the chemically patterned surfaces. As the interface passes throughpatterned surfaces, we observe not only stick-slip of the interface and switching of the contact angles but also the hysteresis of contact point and contact angle. Furthermore, as the size of the patternde creases to zero, the stick-slip becomes weaker but the hysteresis becomes stronger in the sense that one observes either the advancing contact angle or the receding contact angle (when the interface ismoving in the opposite direction) without the switching in between. © 2011 Society for Industrial and Applied Mathematics.

  13. Mean field games with nonlinear mobilities in pedestrian dynamics

    KAUST Repository

    Burger, Martin

    2014-04-01

    In this paper we present an optimal control approach modeling fast exit scenarios in pedestrian crowds. In particular we consider the case of a large human crowd trying to exit a room as fast as possible. The motion of every pedestrian is determined by minimizing a cost functional, which depends on his/her position, velocity, exit time and the overall density of people. This microscopic setup leads in the mean-field limit to a parabolic optimal control problem. We discuss the modeling of the macroscopic optimal control approach and show how the optimal conditions relate to the Hughes model for pedestrian flow. Furthermore we provide results on the existence and uniqueness of minimizers and illustrate the behavior of the model with various numerical results.

  14. Dynamics of a bubble rising in gravitational field

    Directory of Open Access Journals (Sweden)

    De Bernardis Enrico

    2016-03-01

    Full Text Available The rising motion in free space of a pulsating spherical bubble of gas and vapour driven by the gravitational force, in an isochoric, inviscid liquid is investigated. The liquid is at rest at the initial time, so that the subsequent flow is irrotational. For this reason, the velocity field due to the bubble motion is described by means of a potential, which is represented through an expansion based on Legendre polynomials. A system of two coupled, ordinary and nonlinear differential equations is derived for the vertical position of the bubble center of mass and for its radius. This latter equation is a modified form of the Rayleigh-Plesset equation, including a term proportional to the kinetic energy associated to the translational motion of the bubble.

  15. Simulational studies of epitaxial semiconductor superlattices: Quantum dynamical phenomena in ac and dc electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Reynolds, Joseph [Iowa State Univ., Ames, IA (United States)

    1997-10-08

    Using high-accuracy numerical methods the author investigates the dynamics of independent electrons in both ideal and realistic superlattices subject to arbitrary ac and/or dc electric fields. For a variety of superlattice potentials, optically excited initial wave packets, and combinations of ac and dc electric fields, he numerically solves the time-dependent Schroedinger equation. In the case of ideal periodic superlattice potentials, he investigates a long list of dynamical phenomena involving multiple miniband transitions and time-dependent electric fields. These include acceleration effects associated with interminiband transitions in strong fields, Zener resonances between minibands, dynamic localization with ac fields, increased single-miniband transport with an auxiliary resonant ac field, and enhanced or suppressed interminiband probability exchange using an auxiliary ac field. For all of the cases studied, the resulting time-dependent wave function is analyzed by projecting the data onto convenient orthonormal bases. This allows a detailed comparison with approximately analytic treatments. In an effort to explain the rapid decay of experimentally measured Bloch oscillation (BO) signals the author incorporates a one-dimensional representation of interface roughness (IR) into their superlattice potential. He shows that as a result of IR, the electron dynamics can be characterized in terms of many discrete, incommensurate frequencies near the Block frequency. Chapters 2, 3, 4 and 5 have been removed from this report and will be processed separately.

  16. The Lusi mud eruption dynamics: constraints from field data.

    Science.gov (United States)

    Mazzini, Adriano; Sciarra, Alessandra; Lupi, Matteo; Mauri, Guillaume; Karyono, Karyono; Husein, Alwi; Aquino, Ida; Ricco, Ciro; Obermann, Anne; Hadi, Soffian

    2017-04-01

    The Indonesian Lusi eruption has been spewing boiling water, gas, and sediments since the 29th of May 2006. Initially, numerous aligned eruptions sites appeared along the Watukosek fault system that was reactivated after the Yogyakarta earthquake occurring the 27th of May in the Java Island. Since its birth Lusi erupted with a pulsating behavior showing intermittent periods of stronger activity resulting in higher fluids and solid emissions intervals. Since 2010 two active vents are constantly active. We conducted detailed monitoring of such clastic geysering activity and this allowed us to distinguish four distinct phases that follow each other and that reoccur every 30 minutes: (1) regular bubbling activity (constant emission of water, mud breccia, and gas); (2) clastic geysering phase with intense bubbling (consisting in reduced vapor emission and more powerful diffused mud bursting); (3) clastic geysering with mud bursts and intense vapour discharge (typically dense plume that propagates up to 100 m in height); (4) quiescent phase marking the end of the geysering activity (basically no gas emissions or bursts observed). In order to better understand this pulsating behavior and to constrain the mechanisms controlling its activity, we designed a multidisciplinary monitoring of the eruption site combining the deployment of numerous instruments around the crater site. Processing of the collected data reveals the dynamic activity of Lusi's craters. Satellite images show that the location of these vents migrated along a NE-SW direction. This is subparallel to the direction of the Watukosek fault system that is the zone of (left) lateral deformation upon which Lusi developed in 2006. Coupling HR camera images with broadband and short period seismic stations allowed us to describe the seismic signal generated by clastic geysering and to constrain the depth of the source generating the signal. We measure a delay between the seismic (harmonic) record and the associated

  17. A planar elliptical model of cardio-vagal hysteresis

    International Nuclear Information System (INIS)

    Ler, A S H; Cohen, M A; Taylor, J A

    2010-01-01

    The state-dependent portion of cardio-vagal baroreflex control is called baroreflex hyteresis: we observe hysteresis when RR interval and carotid diameter depend on both the direction and value of arterial pressure. The elasticity of arterial walls, as well as the responsiveness of central command reset controls the real-time pattern of neural outflow, which is indirectly measured by RR interval in humans. We model the state-dependent relationship among pressure, vessel diameter and heart rate as a three-dimensional planar ellipse. Two-dimensional projections of this ellipse provide motion direction and quantify hysteresis between mechanical (pressure–diameter), neural (diameter–heart rate), and integrated baroreflex (pressure–heart rate) components. A convenient measure for the magnitude of hysteresis is the ratio of the semi-minor and semi-major axes of the best fitting ellipse. This ratio is given a sign according to the direction of its motion. The signed sum of the hysteresis ratio for vessel mechanics and central neural control reliably predicts cardio-vagal hysteresis. Using this relationship, we can quantify the relative importance of neural versus mechanical contributions to integrated baroreflex responses

  18. Contact Angle Hysteresis on Graphene Surfaces and Hysteresis-free Behavior on Oil-infused Graphite Surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Cyuan-Jhang; Li, Yueh-Feng [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Woon, Wei-Yen [Department of Physics, National Central University, Jhongli 320, Taiwan (China); Sheng, Yu-Jane, E-mail: yjsheng@ntu.edu.tw [Department of Chemical Engineering, National Taiwan University, Taipei 106, Taiwan (China); Tsao, Heng-Kwong, E-mail: hktsao@cc.ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Jhongli 320, Taiwan (China); Department of Physics, National Central University, Jhongli 320, Taiwan (China)

    2016-11-01

    Highlights: • Contact angle hysteresis(CAH) on four graphitic surfacesisinvestigated. • The hysteresis loopof water drops on the polished graphite sheetshowsparticularly small receding contact angle. • The significant CAH observed on CVD graphene and highly oriented pyrolytic graphite is attributed mainly to adhesion hysteresis. • An oil-infused surface of a graphite sheet is produced by imbibition of hexadecane into its porous structure. • The hysteresis-free property for water drops on such a surface is examined and quantitatively explained. - Abstract: Contact angle hysteresis (CAH) on graphitic surfaces, including chemical vapor deposition (CVD) graphene, reduced electrophoretic deposition (EPD) graphene, highly oriented pyrolytic graphite (HOPG), and polished graphite sheet, has been investigated. The hysteresis loops of water drops on the first three samples are similar but the receding contact angle is particularly small for the polished graphite sheet.The significant CAH observed on CVD graphene and HOPG associated with atom-scale roughness has to be attributed mainly to adhesion hysteresis (surface relaxation), instead of roughness or defects.The difference of the wetting behavior among those four graphitic samples has been further demonstrated by hexadecane drops. On the surface of HOPG or CVD graphene,the contact line expands continuously with time, indicating total wetting for which the contact angle does not exist and contact line pinning disappears. In contrast, on the surface of reduced EPD graphene, spontaneous spreading is halted by spikes on it and partial wetting with small contact angle (θ≈4°) is obtained. On the surface of polished graphite sheet, the superlipophilicity and porous structure are demonstrated by imbibition and capillary rise of hexadecane. Consequently, an oil-infused graphite surface can be fabricated and the ultralow CAH of water (∆θ≈2°) is achieved.

  19. Dynamical properties and extremes of Northern Hemisphere climate fields over the past 60 years

    Science.gov (United States)

    Faranda, Davide; Messori, Gabriele; Alvarez-Castro, M. Carmen; Yiou, Pascal

    2017-12-01

    Atmospheric dynamics are described by a set of partial differential equations yielding an infinite-dimensional phase space. However, the actual trajectories followed by the system appear to be constrained to a finite-dimensional phase space, i.e. a strange attractor. The dynamical properties of this attractor are difficult to determine due to the complex nature of atmospheric motions. A first step to simplify the problem is to focus on observables which affect - or are linked to phenomena which affect - human welfare and activities, such as sea-level pressure, 2 m temperature, and precipitation frequency. We make use of recent advances in dynamical systems theory to estimate two instantaneous dynamical properties of the above fields for the Northern Hemisphere: local dimension and persistence. We then use these metrics to characterize the seasonality of the different fields and their interplay. We further analyse the large-scale anomaly patterns corresponding to phase-space extremes - namely time steps at which the fields display extremes in their instantaneous dynamical properties. The analysis is based on the NCEP/NCAR reanalysis data, over the period 1948-2013. The results show that (i) despite the high dimensionality of atmospheric dynamics, the Northern Hemisphere sea-level pressure and temperature fields can on average be described by roughly 20 degrees of freedom; (ii) the precipitation field has a higher dimensionality; and (iii) the seasonal forcing modulates the variability of the dynamical indicators and affects the occurrence of phase-space extremes. We further identify a number of robust correlations between the dynamical properties of the different variables.

  20. Dynamics of quasiparticles in a nonstationary random field

    International Nuclear Information System (INIS)

    Bratus, E.N.; Gredeskul, S.A.; Pastur, L.A.; Shumeiko, V.S.

    1989-01-01

    The problem of nonlinear absorption of a stochastic acoustic signal in superconductors is reduced to an investigation of the states of the one-dimensional Dirac equation in a coordinate system moving with constant velocity and with a random potential. In the present paper a study is made of the properties of the problem of scattering by a random potential that determine the rate of dissipation of the acoustic energy and also of the localized properties of solutions in the case of an infinitely extended signal. If the projection of the Fermi velocity of an electron onto the direction of propagation of the signal is less than the velocity of sound, then all states in the field of an infinitely extended signal are localized (there is a purely point spectrum), and the mean coefficient of transmission of an electron through the region occupied by the sound is exponentially small for a sufficiently long signal. In the opposite case all states are delocalized (the spectrum is absolutely continuous), and on scattering reflection is replaced by partial transformation, for which the mean coefficient of disbalance is exponentially small for a sufficiently long signal

  1. Field Flight Dynamics of Hummingbirds during Territory Encroachment and Defense.

    Science.gov (United States)

    Sholtis, Katherine M; Shelton, Ryan M; Hedrick, Tyson L

    2015-01-01

    Hummingbirds are known to defend food resources such as nectar sources from encroachment by competitors (including conspecifics). These competitive intraspecific interactions provide an opportunity to quantify the biomechanics of hummingbird flight performance during ecologically relevant natural behavior. We recorded the three-dimensional flight trajectories of Ruby-throated Hummingbirds defending, being chased from and freely departing from a feeder. These trajectories allowed us to compare natural flight performance to earlier laboratory measurements of maximum flight speed, aerodynamic force generation and power estimates. During field observation, hummingbirds rarely approached the maximal flight speeds previously reported from wind tunnel tests and never did so during level flight. However, the accelerations and rates of change in kinetic and potential energy we recorded indicate that these hummingbirds likely operated near the maximum of their flight force and metabolic power capabilities during these competitive interactions. Furthermore, although birds departing from the feeder while chased did so faster than freely-departing birds, these speed gains were accomplished by modulating kinetic and potential energy gains (or losses) rather than increasing overall power output, essentially trading altitude for speed during their evasive maneuver. Finally, the trajectories of defending birds were directed toward the position of the encroaching bird rather than the feeder.

  2. Field Flight Dynamics of Hummingbirds during Territory Encroachment and Defense.

    Directory of Open Access Journals (Sweden)

    Katherine M Sholtis

    Full Text Available Hummingbirds are known to defend food resources such as nectar sources from encroachment by competitors (including conspecifics. These competitive intraspecific interactions provide an opportunity to quantify the biomechanics of hummingbird flight performance during ecologically relevant natural behavior. We recorded the three-dimensional flight trajectories of Ruby-throated Hummingbirds defending, being chased from and freely departing from a feeder. These trajectories allowed us to compare natural flight performance to earlier laboratory measurements of maximum flight speed, aerodynamic force generation and power estimates. During field observation, hummingbirds rarely approached the maximal flight speeds previously reported from wind tunnel tests and never did so during level flight. However, the accelerations and rates of change in kinetic and potential energy we recorded indicate that these hummingbirds likely operated near the maximum of their flight force and metabolic power capabilities during these competitive interactions. Furthermore, although birds departing from the feeder while chased did so faster than freely-departing birds, these speed gains were accomplished by modulating kinetic and potential energy gains (or losses rather than increasing overall power output, essentially trading altitude for speed during their evasive maneuver. Finally, the trajectories of defending birds were directed toward the position of the encroaching bird rather than the feeder.

  3. Identification of Dynamic Flow Stress Curves Using the Virtual Fields Methods: Theoretical Feasibility Analysis

    Science.gov (United States)

    Leem, Dohyun; Kim, Jin-Hwan; Barlat, Frédéric; Song, Jung Han; Lee, Myoung-Gyu

    2018-03-01

    An inverse approach based on the virtual fields method (VFM) is presented to identify the material hardening parameters under dynamic deformation. This dynamic-VFM (D-VFM) method does not require load information for the parameter identification. Instead, it utilizes acceleration fields in a specimen's gage region. To investigate the feasibility of the proposed inverse approach for dynamic deformation, the virtual experiments using dynamic finite element simulations were conducted. The simulation could provide all the necessary data for the identification such as displacement, strain, and acceleration fields. The accuracy of the identification results was evaluated by changing several parameters such as specimen geometry, velocity, and traction boundary conditions. The analysis clearly shows that the D-VFM which utilizes acceleration fields can be a good alternative to the conventional identification procedure that uses load information. Also, it was found that proper deformation conditions are required for generating sufficient acceleration fields during dynamic deformation to enhance the identification accuracy with the D-VFM.

  4. Effect of sample shape on nonlinear magnetization dynamics under an external magnetic field

    International Nuclear Information System (INIS)

    Vagin, Dmitry V.; Polyakov, Oleg P.

    2008-01-01

    Effect of sample shape on the nonlinear collective dynamics of magnetic moments in the presence of oscillating and constant external magnetic fields is studied using the Landau-Lifshitz-Gilbert (LLG) approach. The uniformly magnetized sample is considered to be an ellipsoidal axially symmetric particle described by demagnetization factors and uniaxial crystallographic anisotropy formed some angle with an applied field direction. It is investigated as to how the change in particle shape affects its nonlinear magnetization dynamics. To produce a regular study, all results are presented in the form of bifurcation diagrams for all sufficient dynamics regimes of the considered system. In this paper, we show that the sample's (particle's) shape and its orientation with respect to the external field (system configuration) determine the character of magnetization dynamics: deterministic behavior and appearance of chaotic states. A simple change in the system's configuration or in the shapes of its parts can transfer it from chaotic to periodic or even static regime and back. Moreover, the effect of magnetization precession stall and magnetic moments alignment parallel or antiparallel to the external oscillating field is revealed and the way of control of such 'polarized' states is found. Our results suggest that varying the particle's shape and fields' geometry may provide a useful way of magnetization dynamics control in complex magnetic systems

  5. The relativistic mean-field description of nuclei and nuclear dynamics

    International Nuclear Information System (INIS)

    Reinhard, P.G.

    1989-01-01

    The relativistic mean-field model of the nucleus is reviewed. It describes the nucleus as a system of Dirac-Nucleons which interact in a relativistic covariant manner via meson fields. The meson fields are treated as mean fields, i.e. as non quantal c-number fields. The effects of the Dirac sea of the nucleons is neglected. The model is interpreted as a phenomenological ansatz providing a selfconsistent relativistic description of nuclei and nuclear dynamics. It is viewed, so to say, as the relativistic generalisation of the Skyrme-Hartree-Fock ansatz. The capability and the limitations of the model to describe nuclear properties are discussed. Recent applications to spherical and deformed nuclei and to nuclear dynamics are presented. (orig.)

  6. Understanding Angiography-Based Aneurysm Flow Fields through Comparison with Computational Fluid Dynamics.

    Science.gov (United States)

    Cebral, J R; Mut, F; Chung, B J; Spelle, L; Moret, J; van Nijnatten, F; Ruijters, D

    2017-06-01

    Hemodynamics is thought to be an important factor for aneurysm progression and rupture. Our aim was to evaluate whether flow fields reconstructed from dynamic angiography data can be used to realistically represent the main flow structures in intracranial aneurysms. DSA-based flow reconstructions, obtained during interventional treatment, were compared qualitatively with flow fields obtained from patient-specific computational fluid dynamics models and quantitatively with projections of the computational fluid dynamics fields (by computing a directional similarity of the vector fields) in 15 cerebral aneurysms. The average similarity between the DSA and the projected computational fluid dynamics flow fields was 78% in the parent artery, while it was only 30% in the aneurysm region. Qualitatively, both the DSA and projected computational fluid dynamics flow fields captured the location of the inflow jet, the main vortex structure, the intrasaccular flow split, and the main rotation direction in approximately 60% of the cases. Several factors affect the reconstruction of 2D flow fields from dynamic angiography sequences. The most important factors are the 3-dimensionality of the intrasaccular flow patterns and inflow jets, the alignment of the main vortex structure with the line of sight, the overlapping of surrounding vessels, and possibly frame rate undersampling. Flow visualization with DSA from >1 projection is required for understanding of the 3D intrasaccular flow patterns. Although these DSA-based flow quantification techniques do not capture swirling or secondary flows in the parent artery, they still provide a good representation of the mean axial flow and the corresponding flow rate. © 2017 by American Journal of Neuroradiology.

  7. Frequency-dependent local field factors in dielectric liquids by a polarizable force field and molecular dynamics simulations

    International Nuclear Information System (INIS)

    Davari, Nazanin; Haghdani, Shokouh; Åstrand, Per-Olof

    2015-01-01

    A force field model for calculating local field factors, i.e. the linear response of the local electric field for example at a nucleus in a molecule with respect to an applied electric field, is discussed. It is based on a combined charge-transfer and point-dipole interaction model for the polarizability, and thereby it includes two physically distinct terms for describing electronic polarization: changes in atomic charges arising from transfer of charge between the atoms and atomic induced dipole moments. A time dependence is included both for the atomic charges and the atomic dipole moments and if they are assumed to oscillate with the same frequency as the applied electric field, a model for frequency-dependent properties are obtained. Furthermore, if a life-time of excited states are included, a model for the complex frequency-dependent polariability is obtained including also information about excited states and the absorption spectrum. We thus present a model for the frequency-dependent local field factors through the first molecular excitation energy. It is combined with molecular dynamics simulations of liquids where a large set of configurations are sampled and for which local field factors are calculated. We are normally not interested in the average of the local field factor but rather in configurations where it is as high as possible. In electrical insulation, we would like to avoid high local field factors to reduce the risk for electrical breakdown, whereas for example in surface-enhanced Raman spectroscopy, high local field factors are desired to give dramatically increased intensities

  8. Magnetohydrodynamic Modeling of Solar Coronal Dynamics with an Initial Non-force-free Magnetic Field

    Energy Technology Data Exchange (ETDEWEB)

    Prasad, A.; Bhattacharyya, R.; Kumar, Sanjay [Udaipur Solar Observatory, Physical Research Laboratory, Dewali, Bari Road, Udaipur-313001 (India)

    2017-05-01

    The magnetic fields in the solar corona are generally neither force-free nor axisymmetric and have complex dynamics that are difficult to characterize. Here we simulate the topological evolution of solar coronal magnetic field lines (MFLs) using a magnetohydrodynamic model. The simulation is initialized with a non-axisymmetric non-force-free magnetic field that best correlates with the observed vector magnetograms of solar active regions (ARs). To focus on these ideas, simulations are performed for the flaring AR 11283 noted for its complexity and well-documented dynamics. The simulated dynamics develops as the initial Lorentz force pushes the plasma and facilitates successive magnetic reconnections at the two X-type null lines present in the initial field. Importantly, the simulation allows for the spontaneous development of mass flow, unique among contemporary works, that preferentially reconnects field lines at one of the X-type null lines. Consequently, a flux rope consisting of low-lying twisted MFLs, which approximately traces the major polarity inversion line, undergoes an asymmetric monotonic rise. The rise is attributed to a reduction in the magnetic tension force at the region overlying the rope, resulting from the reconnection. A monotonic rise of the rope is in conformity with the standard scenario of flares. Importantly, the simulated dynamics leads to bifurcations of the flux rope, which, being akin to the observed filament bifurcation in AR 11283, establishes the appropriateness of the initial field in describing ARs.

  9. Contact Hysteresis and Friction of Alkanethiol SAMs on Au

    Energy Technology Data Exchange (ETDEWEB)

    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.

  10. A Memory-Based Hysteresis Model in Piezoelectric Actuators

    Directory of Open Access Journals (Sweden)

    Guilin Zhang

    2012-01-01

    Full Text Available A mathematical memory-based model is proposed to capture the hysteresis behavior in piezoelectric actuators. It is observed that the ascending (descending hysteresis curves are alike and converge to one point without memory saturation. Therefore, two, dominant curves are determined and expressed as continuous functions, and the other hysteresis curves are modeled using two dominant curves through nonlinear transforming of coordinate axis. In the event of memory saturation, a new converging point is used to compensate the model prediction error. The experimental study has been carried out and our proposed model prediction method is compared with PI model and the linear model. It shows that the proposed model prediction method is better than other two methods.

  11. Nonlinear friction modelling and compensation control of hysteresis phenomena for a pair of tendon-sheath actuated surgical robots

    Science.gov (United States)

    Do, T. N.; Tjahjowidodo, T.; Lau, M. W. S.; Phee, S. J.

    2015-08-01

    Natural Orifice Transluminal Endoscopic Surgery (NOTES) is a special method that allows surgical operations via natural orifices like mouth, anus, and vagina, without leaving visible scars. The use of flexible tendon-sheath mechanism (TSM) is common in these systems because of its light weight in structure, flexibility, and easy transmission of power. However, nonlinear friction and backlash hysteresis pose many challenges to control of such systems; in addition, they do not provide haptic feedback to assist the surgeon in the operation of the systems. In this paper, we propose a new dynamic friction model and backlash hysteresis nonlinearity for a pair of TSM to deal with these problems. The proposed friction model, unlike current approaches in the literature, is smooth and able to capture the force at near zero velocity when the system is stationary or operates at small motion. This model can be used to estimate the friction force for haptic feedback purpose. To improve the system tracking performances, a backlash hysteresis model will be introduced, which can be used in a feedforward controller scheme. The controller involves a simple computation of the inverse hysteresis model. The proposed models are configuration independent and able to capture the nonlinearities for arbitrary tendon-sheath shapes. A representative experimental setup is used to validate the proposed models and to demonstrate the improvement in position tracking accuracy and the possibility of providing desired force information at the distal end of a pair of TSM slave manipulator for haptic feedback to the surgeons.

  12. Spin tunnelling dynamics for spin-1 Bose-Einstein condensates in a swept magnetic field

    International Nuclear Information System (INIS)

    Wang Guanfang; Fu Libin; Liu Jie

    2008-01-01

    We investigate the spin tunnelling of spin-1 Bose-Einstein condensates in a linearly swept magnetic field with a mean-field treatment. We focus on the two typical alkali Bose atoms 87 Rb and 23 Na condensates and study their tunnelling dynamics according to the sweep rates of the external magnetic fields. In the adiabatic (i.e. slowly sweeping) and sudden (i.e. fast sweeping) limits, no tunnelling is observed. For the case of moderate sweep rates, the tunnelling dynamics is found to be very sensitive to the sweep rates, so the plots of tunnelling probability versus sweep rate only become resolvable at a resolution of 10 -4 G s -1 . Moreover, a conserved quantity standing for the magnetization in experiments is found to affect dramatically the dynamics of the spin tunnelling. Theoretically we have given a complete interpretation of the above findings, and our studies could stimulate the experimental study of spinor Bose-Einstein condensates

  13. Thermo field dynamics in the treatment of the nuclear pairing problem at finite temperature

    International Nuclear Information System (INIS)

    Civitarese, O.; DePaoli, A.L.

    1993-01-01

    The use of the thermo field dynamics, in dealing with the study of nuclear properties at finite temperature, is discussed for the case of a nuclear Hamiltonian which includes a single-particle term and a monopole pairing residual two-body interaction. The rules of the thermo fields dynamics are applied to double the Hilbert space, thus accounting for the thermal occupation of single-particle states, and to construct dual spaces, both for single-particle (BCS) and collective (RPA) degrees of freedom. It is shown that the rules of the thermo field dynamics yield to a temperature dependence of the equations describing quasiparticle and phonon excitations which is similar to the one found in the more conventional finite temperature Wick's theorem approach, namely: By dealing with thermal averages. (orig.)

  14. Dynamical polarizability of graphene irradiated by circularly polarized ac electric fields

    DEFF Research Database (Denmark)

    Busl, Maria; Platero, Gloria; Jauho, Antti-Pekka

    2012-01-01

    We examine the low-energy physics of graphene in the presence of a circularly polarized electric field in the terahertz regime. Specifically, we derive a general expression for the dynamical polarizability of graphene irradiated by an ac electric field. Several approximations are developed...... that allow one to develop a semianalytical theory for the weak-field regime. The ac field changes qualitatively the single- and many-electron excitations of graphene: Undoped samples may exhibit collective excitations (in contrast to the equilibrium situation), and the properties of the excitations in doped...

  15. On generally covariant quantum field theory and generalized causal and dynamical structures

    International Nuclear Information System (INIS)

    Bannier, U.

    1988-01-01

    We give an example of a generally covariant quasilocal algebra associated with the massive free field. Maximal, two-sided ideals of this algebra are algebraic representatives of external metric fields. In some sense, this algebra may be regarded as a concrete realization of Ekstein's ideas of presymmetry in quantum field theory. Using ideas from our example and from usual algebraic quantum field theory, we discuss a generalized scheme, in which maximal ideals are viewed as algebraic representatives of dynamical equations or Lagrangians. The considered frame is no quantum gravity, but may lead to further insight into the relation between quantum theory and space-time geometry. (orig.)

  16. Magnetic field measurements of Fermilab/General Dynamics built full scale SSC collider dipole magnets

    International Nuclear Information System (INIS)

    Delchamps, S.; Bleadon, M.; Bossert, R.; Carson, J.; Gourlay, S.; Hanft, R.; Koska, W.; Kuchnir, M.; Lamm, M.J.; Mazur, P.O.; Mokhtarani, A.; Orris, D.; Strait, J.; Wake, M.; Devred, A.; DiMarco, J.; Kuzminski, J.; Ogitsu, T.; Puglisi, M.; Tompkins, J.C.; Yu, Y.; Zhao, Y.; Zheng, H.

    1992-01-01

    This paper presents preliminary results of magnetic field measurements made on a series of 50 mm aperture 15 m long SSC collider dipole magnets designed and manufactured at Fermi National Accelerator Laboratory (Fermilab) for use in the Superconducting Super Collider Laboratory (SSCL) Accelerator System String Test. The magnets were assembled by Fermilab and General Dynamics personnel, and were tested at the Magnet Test Facility (MTF) at Fermilab. Measurements of the dipole field angle, dipole field strength, and field shape parameters at various stages in magnet construction and testing are described

  17. Data use investigation for the magnetic field satellite (MAGSAT) mission: Geomagnetic field forecasting and fluid dynamics of the core

    Science.gov (United States)

    Benton, E. R. (Principal Investigator)

    1982-01-01

    MAGSAT data were used to construct a variety of spherical harmonic models of the main geomagnetic field emanating from Earth's liquid core at poch 1980. These models were used to: (1) accurately determine the radius of Earth's core by a magnetic method, (2) calculate estimates, of the long-term ange of variation of geomagnetic Gauss coefficients; (3) establish a preferred truncation level for current spherical harmonic models of the main geomagnetic field from the core; (4) evaluate a method for taking account of electrical conduction in the mantle when the magnetic field is downward continued to the core-mantle boundary; and (5) establish that upwelling and downwelling of fluid motion at the top of the core is probably detectable, observationally. A fluid dynamics forecast model was not produced because of insufficient data.

  18. Self-modulated dynamics of a relativistic charged particle beam in plasma wake field excitation

    Energy Technology Data Exchange (ETDEWEB)

    Akhter, T.; Fedele, R. [Dipartimento di Fisica ‘Ettore Pancini’, Università di Napoli Federico II and INFN Sezione di Napoli, Napoli (Italy); Nicola, S. De [CNR-SPIN and INFN Sezione di Napoli, Napoli (Italy); Tanjia, F. [Dipartimento di Fisica ‘Ettore Pancini’, Università di Napoli Federico II and INFN Sezione di Napoli, Napoli (Italy); Jovanović, D. [Institute of Physics, University of Belgrade, Belgrade (Serbia); Mannan, A. [Department of Physics, Jahangirnagar University, Savar, Dhaka (Bangladesh)

    2016-09-01

    The self-modulated dynamics of a relativistic charged particle beam is provided within the context of the theory of plasma wake field excitation. The self-consistent description of the beam dynamics is provided by coupling the Vlasov equation with a Poisson-type equation relating the plasma wake potential to the beam density. An analysis of the beam envelope self-modulation is then carried out and the criteria for the occurrence of the instability are discussed thereby.

  19. Learning the condition of satisfaction of an elementary behavior in dynamic field theory

    OpenAIRE

    Luciw, M; Kazerounian, S; Lahkman, K; Richter, M; Sandamirskaya, Y

    2015-01-01

    In order to proceed along an action sequence, an autonomous agent has to recognize that the intended final condition of the previous action has been achieved. In previous work, we have shown how a sequence of actions can be generated by an embodied agent using a neural-dynamic architecture for behavioral organization, in which each action has an intention and condition of satisfaction. These components are represented by dynamic neural fields, and are coupled to motors...

  20. Theoretical study of the dynamic magnetic response of ferrofluid to static and alternating magnetic fields

    International Nuclear Information System (INIS)

    Batrudinov, Timur M.; Ambarov, Alexander V.; Elfimova, Ekaterina A.; Zverev, Vladimir S.; Ivanov, Alexey O.

    2017-01-01

    The dynamic magnetic response of ferrofluid in a static uniform external magnetic field to a weak, linear polarized, alternating magnetic field is investigated theoretically. The ferrofluid is modeled as a system of dipolar hard spheres, suspended in a long cylindrical tube whose long axis is parallel to the direction of the static and alternating magnetic fields. The theory is based on the Fokker-Planck-Brown equation formulated for the case when the both static and alternating magnetic fields are applied. The solution of the Fokker-Planck-Brown equation describing the orientational probability density of a randomly chosen dipolar particle is expressed as a series in terms of the spherical Legendre polynomials. The obtained analytical expression connecting three neighboring coefficients of the series makes possible to determine the probability density with any order of accuracy in terms of Legendre polynomials. The analytical formula for the probability density truncated at the first Legendre polynomial is evaluated and used for the calculation of the magnetization and dynamic susceptibility spectra. In the absence of the static magnetic field the presented theory gives the correct single-particle Debye-theory result, which is the exact solution of the Fokker-Planck-Brown equation for the case of applied weak alternating magnetic field. The influence of the static magnetic field on the dynamic susceptibility is analyzed in terms of the low-frequency behavior of the real part and the position of the peak in the imaginary part. - Highlights: • The dynamic magnetic response of ferrofluid is investigated theoretically. • The static and alternating magnetic fields are applied along the Oz-axis. • Theory is based on the Fokker-Planck-Brown equation (FPBe). • The solution of FPBe is expressed as a series in terms of the Legendre polynomials. • The influence of static magnetic field on susceptibility spectra is analyzed.

  1. Modeling the hysteresis of a scanning probe microscope

    DEFF Research Database (Denmark)

    Dirscherl, Kai; Garnæs, Jørgen; Nielsen, L.

    2000-01-01

    Most scanning probe microscopes use piezoelectric actuators in open loop configurations. Therefore a major problem related to these instruments is the image distortion due to the hysteresis effect of the piezo. In order to eliminate the distortions, cost effective software control based on a model....... The structures were scanned for different scan ranges varying from 5 V peak to peak to 440 V peak to peak, so that 99% of the scanners' full motion range was covered. A least-squares fit of the experiments to the hysteresis model provided standard deviations per scan range of around 0.2%. This represents...

  2. Hysteresis Phenomena in Sulfur Dioxide Oxidation over Supported Vanadium Catalysts

    DEFF Research Database (Denmark)

    Masters, Stephen G.; Eriksen, Kim Michael; Fehrmann, Rasmus

    1997-01-01

    Catalyst deactivation and hysteresis behavior in industrial SO2-oxidation catalysts have been studied in the temperature region 350-480 C by combined in situ EPR spectroscopy and catalytic activity measurements. The feed gas composition simulated sulfuric acid synthesis gas and wet/dry deNOx'ed f......NOx'ed flue gas. The vanadium (IV) compound K4(VO)3(SO4)5 precipitated during all the investigated conditions hence causing catalyst deactivation. Hysteresis behavior of both the catalytic activity and the V(IV) content was observed during reheating....

  3. Intrinsic Low Hysteresis Touch Mode Capacitive Pressure Sensor

    DEFF Research Database (Denmark)

    Fragiacomo, Giulio; Pedersen, Thomas; Hansen, Ole

    2011-01-01

    Hysteresis has always been one of the main concerns when fabricating touch mode capacitive pressure sensors (TMCPS). This phenomenon can be fought at two different levels: during fabrication or after fabrication with the aid of a dedicated signal conditioning circuit. We will describe a microfabr......Hysteresis has always been one of the main concerns when fabricating touch mode capacitive pressure sensors (TMCPS). This phenomenon can be fought at two different levels: during fabrication or after fabrication with the aid of a dedicated signal conditioning circuit. We will describe...... in the touch mode region....

  4. Implementation of sorption hysteresis in multi-Fickian moisture transport

    DEFF Research Database (Denmark)

    Frandsen, Henrik Lund; Svensson, Staffan

    2007-01-01

    In the cellular structure of wood, bound-water diffusion and water-vapor diffusion interact via sorption in a complex moisture-transportation system. At low relative humidities, moisture transport may be modeled by a Fickian diffusion equation with a good approximation. At higher relative......-35% in moisture content. Hence, for a precise moisture content computation, sorption hysteresis must be taken into account. The present paper explains the relation between sorption hysteresis and multi-Fickian moisture transport, and clarifies how models for the two phenomena are coupled. To illustrate...

  5. Hysteresis of boiling for different tunnel-pore surfaces

    Directory of Open Access Journals (Sweden)

    Pastuszko Robert

    2015-01-01

    Full Text Available 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.

  6. Exact Double Counting in Combining the Dynamical Mean Field Theory and the Density Functional Theory.

    Science.gov (United States)

    Haule, Kristjan

    2015-11-06

    We propose a continuum representation of the dynamical mean field theory, in which we were able to derive an exact overlap between the dynamical mean field theory and band structure methods, such as the density functional theory; double counting. The implementation of this exact double counting shows improved agreement between the theory and experiment in several correlated solids, such as the transition metal oxides and lanthanides. Previously introduced nominal double counting is in much better agreement with the exact double counting than the most widely used fully localized limit formula.

  7. Corrections for hysteresis curves for rare earth magnet materials measured by open magnetic circuit methods

    International Nuclear Information System (INIS)

    Nakagawa, Yasuaki

    1996-01-01

    The methods for testing permanent magnets stipulated in the usual industrial standards are so-called closed magnetic circuit methods which employ a loop tracer using an iron-core electromagnet. If the coercivity exceeds the highest magnetic field generated by the electromagnet, full hysteresis curves cannot be obtained. In the present work, magnetic fields up to 15 T were generated by a high-power water-cooled magnet, and the magnetization was measured by an induction method with an open magnetic circuit, in which the effect of a demagnetizing field should be taken into account. Various rare earth magnets materials such as sintered or bonded Sm-Co and Nd-Fe-B were provided by a number of manufacturers. Hysteresis curves for cylindrical samples with 10 nm in diameter and 2 mm, 3.5 mm, 5 mm, 14 mm or 28 mm in length were measured. Correction for the demagnetizing field is rather difficult because of its non-uniformity. Roughly speaking, a mean demagnetizing factor for soft magnetic materials can be used for the correction, although the application of this factor to hard magnetic material is hardly justified. Thus the dimensions of the sample should be specified when the data obtained by the open magnetic circuit method are used as industrial standards. (author)

  8. Testing for the ‘predictability’ of dynamically triggered earthquakes in Geysers Geothermal Field

    Science.gov (United States)

    Aiken, Chastity; Meng, Xiaofeng; Hardebeck, Jeanne L.

    2018-01-01

    The Geysers geothermal field is well known for being susceptible to dynamic triggering of earthquakes by large distant earthquakes, owing to the introduction of fluids for energy production. Yet, it is unknown if dynamic triggering of earthquakes is ‘predictable’ or whether dynamic triggering could lead to a potential hazard for energy production. In this paper, our goal is to investigate the characteristics of triggering and the physical conditions that promote triggering to determine whether or not triggering is in anyway foreseeable. We find that, at present, triggering in The Geysers is not easily ‘predictable’ in terms of when and where based on observable physical conditions. However, triggered earthquake magnitude positively correlates with peak imparted dynamic stress, and larger dynamic stresses tend to trigger sequences similar to mainshock–aftershock sequences. Thus, we may be able to ‘predict’ what size earthquakes to expect at The Geysers following a large distant earthquake.

  9. Testing for the 'predictability' of dynamically triggered earthquakes in The Geysers geothermal field

    Science.gov (United States)

    Aiken, Chastity; Meng, Xiaofeng; Hardebeck, Jeanne

    2018-03-01

    The Geysers geothermal field is well known for being susceptible to dynamic triggering of earthquakes by large distant earthquakes, owing to the introduction of fluids for energy production. Yet, it is unknown if dynamic triggering of earthquakes is 'predictable' or whether dynamic triggering could lead to a potential hazard for energy production. In this paper, our goal is to investigate the characteristics of triggering and the physical conditions that promote triggering to determine whether or not triggering is in anyway foreseeable. We find that, at present, triggering in The Geysers is not easily 'predictable' in terms of when and where based on observable physical conditions. However, triggered earthquake magnitude positively correlates with peak imparted dynamic stress, and larger dynamic stresses tend to trigger sequences similar to mainshock-aftershock sequences. Thus, we may be able to 'predict' what size earthquakes to expect at The Geysers following a large distant earthquake.

  10. Dynamic wave field synthesis: enabling the generation of field distributions with a large space-bandwidth product.

    Science.gov (United States)

    Kamau, Edwin N; Heine, Julian; Falldorf, Claas; Bergmann, Ralf B

    2015-11-02

    We present a novel approach for the design and fabrication of multiplexed computer generated volume holograms (CGVH) which allow for a dynamic synthesis of arbitrary wave field distributions. To achieve this goal, we developed a hybrid system that consists of a CGVH as a static element and an electronically addressed spatial light modulator as the dynamic element. We thereby derived a new model for describing the scattering process within the inhomogeneous dielectric material of the hologram. This model is based on the linearization of the scattering process within the Rytov approximation and incorporates physical constraints that account for voxel based laser-lithography using micro-fabrication of the holograms in a nonlinear optical material. In this article we demonstrate that this system basically facilitates a high angular Bragg selectivity on the order of 1°. Additionally, it allows for a qualitatively low cross-talk dynamic synthesis of predefined wave fields with a much larger space-bandwidth product (SBWP ≥ 8.7 × 10(6)) as compared to the current state of the art in computer generated holography.

  11. Hysteresis of targeting civilians in armed conflicts

    OpenAIRE

    Uih Ran Lee

    2015-01-01

    This article explores warring groups’ intentional targeting behavior against civilians, a strictly prohibited war strategy by international norms. Using dynamic panel regressions run on a comprehensive dataset of contemporary warfare which covers 22 years (1989-2010), I find that warring actors, both sovereign states and formally organized armed groups, behave systematically in terms of civilian targeting when they are involved in prolonged armed conflict (15-22 years). Warring actors’ lethal...

  12. Dynamic Model of MR Dampers Based on a Hysteretic Magnetic Circuit

    Directory of Open Access Journals (Sweden)

    Pengfei Guo

    2018-01-01

    Full Text Available As a key to understand dynamic performances of MR dampers, a comprehensive dynamic magnetic circuit model is proposed in this work on the basis of Ampere’s and Gauss’s laws. It takes into account not only the magnetic saturation, which many existing studies have focused on, but also the magnetic hysteresis and eddy currents in a MR damper. The hysteresis of steel parts of MR dampers is described by Jiles-Atherton (J-A models, and the eddy current is included based on the field separation. Compared with the FEM results, the proposed model is validated in low- and high-frequency studies for the predictions of the magnetic saturation, the hysteresis, and the effect of eddy currents. A simple multiphysics model is developed to demonstrate how to combine the proposed magnetic circuit model with the commonly used Bingham fluid model. The damping force in the high-frequency case obviously lags behind the coil current, which exhibits a hysteresis loop in the current-force plane. The lag of damping force even exists in a low-frequency varying magnetic field and becomes more severe in the presence of eddy currents.

  13. Exchange bias and asymmetric hysteresis loops from a microscopic model of core/shell nanoparticles

    International Nuclear Information System (INIS)

    Iglesias, Oscar; Batlle, Xavier; Labarta, Amilcar

    2007-01-01

    We present Monte Carlo simulations of hysteresis loops of a model of a magnetic nanoparticle with a ferromagnetic core and an antiferromagnetic shell with varying values of the core/shell interface exchange coupling which aim to clarify the microscopic origin of exchange bias observed experimentally. We have found loop shifts in the field direction as well as displacements along the magnetization axis that increase in magnitude when increasing the interfacial exchange coupling. Overlap functions computed from the spin configurations along the loops have been obtained to explain the origin and magnitude of these features microscopically

  14. Low-field vortex dynamics in various high-Tc thin films

    Indian Academy of Sciences (India)

    We present a novel ac susceptibility technique for the study of vortex creep in supercon- ducting thin films. With this technique we study the dynamics of dilute vortices in c-axis oriented. Y-123, Hg-1212, and Tl-1212 ... ramp the field up and down a value ± H about the dc field of interest and study the re- laxation through the ...

  15. Computational strong-field quantum dynamics intense light-matter interactions

    CERN Document Server

    2017-01-01

    This graduate textbook introduces the computational techniques to study ultra-fast quantum dynamics of matter exposed to strong laser fields. Coverage includes methods to propagate wavefunctions according to the time-dependent Schrödinger, Klein-Gordon or Dirac equation, the calculation of typical observables, time-dependent density functional theory, multi-configurational time-dependent Hartree-Fock, time-dependent configuration interaction singles, the strong-field approximation, and the microscopic particle-in-cell approach.

  16. Conformal field theory as microscopic dynamics of incompressible Euler and Navier-Stokes equations.

    Science.gov (United States)

    Fouxon, Itzhak; Oz, Yaron

    2008-12-31

    We consider the hydrodynamics of relativistic conformal field theories at finite temperature. We show that the limit of slow motions of the ideal hydrodynamics leads to the nonrelativistic incompressible Euler equation. For viscous hydrodynamics we show that the limit of slow motions leads to the nonrelativistic incompressible Navier-Stokes equation. We explain the physical reasons for the reduction and discuss the implications. We propose that conformal field theories provide a fundamental microscopic viewpoint of the equations and the dynamics governed by them.

  17. Conformal Field Theory as Microscopic Dynamics of Incompressible Euler and Navier-Stokes Equations

    International Nuclear Information System (INIS)

    Fouxon, Itzhak; Oz, Yaron

    2008-01-01

    We consider the hydrodynamics of relativistic conformal field theories at finite temperature. We show that the limit of slow motions of the ideal hydrodynamics leads to the nonrelativistic incompressible Euler equation. For viscous hydrodynamics we show that the limit of slow motions leads to the nonrelativistic incompressible Navier-Stokes equation. We explain the physical reasons for the reduction and discuss the implications. We propose that conformal field theories provide a fundamental microscopic viewpoint of the equations and the dynamics governed by them

  18. Computational strong-field quantum dynamics. Intense light-matter interactions

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Dieter (ed.) [Rostock Univ. (Germany). Inst. fuer Physik

    2017-09-01

    This graduate textbook introduces the computational techniques to study ultra-fast quantum dynamics of matter exposed to strong laser fields. Coverage includes methods to propagate wavefunctions according to the time dependent Schroedinger, Klein-Gordon or Dirac equation, the calculation of typical observables, time-dependent density functional theory, multi configurational time-dependent Hartree-Fock, time-dependent configuration interaction singles, the strong-field approximation, and the microscopic particle-in-cell approach.

  19. Magnetic hysteresis at the domain scale of a multi-scale material model for magneto-elastic behaviour

    International Nuclear Information System (INIS)

    Vanoost, D.; Steentjes, S.; Peuteman, J.; Gielen, G.; De Gersem, H.; Pissoort, D.; Hameyer, K.

    2016-01-01

    This paper proposes a multi-scale energy-based material model for poly-crystalline materials. Describing the behaviour of poly-crystalline materials at three spatial scales of dominating physical mechanisms allows accounting for the heterogeneity and multi-axiality of the material behaviour. The three spatial scales are the poly-crystalline, grain and domain scale. Together with appropriate scale transitions rules and models for local magnetic behaviour at each scale, the model is able to describe the magneto-elastic behaviour (magnetostriction and hysteresis) at the macroscale, although the data input is merely based on a set of physical constants. Introducing a new energy density function that describes the demagnetisation field, the anhysteretic multi-scale energy-based material model is extended to the hysteretic case. The hysteresis behaviour is included at the domain scale according to the micro-magnetic domain theory while preserving a valid description for the magneto-elastic coupling. The model is verified using existing measurement data for different mechanical stress levels. - Highlights: • A ferromagnetic hysteretic energy-based multi-scale material model is proposed. • The hysteresis is obtained by new proposed hysteresis energy density function. • Avoids tedious parameter identification.

  20. Magnetic hysteresis at the domain scale of a multi-scale material model for magneto-elastic behaviour

    Energy Technology Data Exchange (ETDEWEB)

    Vanoost, D., E-mail: dries.vanoost@kuleuven-kulak.be [KU Leuven Technology Campus Ostend, ReMI Research Group, Oostende B-8400 (Belgium); KU Leuven Kulak, Wave Propagation and Signal Processing Research Group, Kortrijk B-8500 (Belgium); Steentjes, S. [Institute of Electrical Machines, RWTH Aachen University, Aachen D-52062 (Germany); Peuteman, J. [KU Leuven Technology Campus Ostend, ReMI Research Group, Oostende B-8400 (Belgium); KU Leuven, Department of Electrical Engineering, Electrical Energy and Computer Architecture, Heverlee B-3001 (Belgium); Gielen, G. [KU Leuven, Department of Electrical Engineering, Microelectronics and Sensors, Heverlee B-3001 (Belgium); De Gersem, H. [KU Leuven Kulak, Wave Propagation and Signal Processing Research Group, Kortrijk B-8500 (Belgium); TU Darmstadt, Institut für Theorie Elektromagnetischer Felder, Darmstadt D-64289 (Germany); Pissoort, D. [KU Leuven Technology Campus Ostend, ReMI Research Group, Oostende B-8400 (Belgium); KU Leuven, Department of Electrical Engineering, Microelectronics and Sensors, Heverlee B-3001 (Belgium); Hameyer, K. [Institute of Electrical Machines, RWTH Aachen University, Aachen D-52062 (Germany)

    2016-09-15

    This paper proposes a multi-scale energy-based material model for poly-crystalline materials. Describing the behaviour of poly-crystalline materials at three spatial scales of dominating physical mechanisms allows accounting for the heterogeneity and multi-axiality of the material behaviour. The three spatial scales are the poly-crystalline, grain and domain scale. Together with appropriate scale transitions rules and models for local magnetic behaviour at each scale, the model is able to describe the magneto-elastic behaviour (magnetostriction and hysteresis) at the macroscale, although the data input is merely based on a set of physical constants. Introducing a new energy density function that describes the demagnetisation field, the anhysteretic multi-scale energy-based material model is extended to the hysteretic case. The hysteresis behaviour is included at the domain scale according to the micro-magnetic domain theory while preserving a valid description for the magneto-elastic coupling. The model is verified using existing measurement data for different mechanical stress levels. - Highlights: • A ferromagnetic hysteretic energy-based multi-scale material model is proposed. • The hysteresis is obtained by new proposed hysteresis energy density function. • Avoids tedious parameter identification.

  1. Influence of the applied elastic tensile and compressive stress on the hysteresis curves of Fe-3%Si non-oriented steel

    Energy Technology Data Exchange (ETDEWEB)

    Perevertov, O., E-mail: perever@fzu.cz

    2017-04-15

    The influence of applied elastic tensile stress up to 120 MPa and compressive stress up to 35 MPa on the magnetic hysteresis curves of non-oriented Fe-3%Si steel is studied. In two tensile stress ranges the hysteresis loop changed monotonously – low stress below 10 MPa facilitated the magnetization process, while above 15 MPa tension deteriorated magnetic properties. This difference in behavior corresponds to two different mechanisms – 1) favoring by tensile stress magnetic easy axes closest to the filed direction and 2) appearance of large demagnetizing fields at grain boundaries and the sample surface. Compression continuously deteriorated magnetic properties and made the hysteresis loop constricted above a few MPa. The effective field as a product of two functions – of the magnetization and of the stress gave excellent agreement with experimental curves for both tensile stress ranges and for compression. The sensitivity of magnetization to compression was approximately five times larger than to tension. The complex hysteresis loop behavior under tension and compression was explained on the basis of our previous results on stressed grain-oriented steel of the same composition, in which the magnetic domains were also studied. - Highlights: • Tensile and compressive elastic stress was applied to non-oriented Fe-3%Si steel. • Hysteresis loops were successfully modeled using stress-induced effective field. • Results were explained on the basis of previous studies on grain-oriented samples.

  2. Review of the Dynamics of Coalescence and Demulsification by High-Voltage Pulsed Electric Fields

    Directory of Open Access Journals (Sweden)

    Ye Peng

    2016-01-01

    Full Text Available The coalescence of droplets in oil can be implemented rapidly by high-voltage pulse electric field, which is an effective demulsification dehydration technological method. At present, it is widely believed that the main reason of pulse electric field promoting droplets coalescence is the dipole coalescence and oscillation coalescence in pulse electric field, and the optimal coalescence pulse electric field parameters exist. Around the above content, the dynamics of high-voltage pulse electric field promoting the coalescence of emulsified droplets is studied by researchers domestically and abroad. By review, the progress of high-voltage pulse electric field demulsification technology can get a better understanding, which has an effect of throwing a sprat to catch a whale on promoting the industrial application.

  3. Design of a surgical robot with dynamic vision field control for Single Port Endoscopic Surgery.

    Science.gov (United States)

    Kobayashi, Yo; Sekiguchi, Yuta; Tomono, Yu; Watanabe, Hiroki; Toyoda, Kazutaka; Konishi, Kozo; Tomikawa, Morimasa; Ieiri, Satoshi; Tanoue, Kazuo; Hashizume, Makoto; Fujie, Masaktsu G

    2010-01-01

    Recently, a robotic system was developed to assist Single Port Endoscopic Surgery (SPS). However, the existing system required a manual change of vision field, hindering the surgical task and increasing the degrees of freedom (DOFs) of the manipulator. We proposed a surgical robot for SPS with dynamic vision field control, the endoscope view being manipulated by a master controller. The prototype robot consisted of a positioning and sheath manipulator (6 DOF) for vision field control, and dual tool tissue manipulators (gripping: 5DOF, cautery: 3DOF). Feasibility of the robot was demonstrated in vitro. The "cut and vision field control" (using tool manipulators) is suitable for precise cutting tasks in risky areas while a "cut by vision field control" (using a vision field control manipulator) is effective for rapid macro cutting of tissues. A resection task was accomplished using a combination of both methods.

  4. Effective-field theory for dynamic phase diagrams of the kinetic spin-3/2 Blume–Capel model under a time oscillating longitudinal field

    Energy Technology Data Exchange (ETDEWEB)

    Ertaş, Mehmet [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Kocakaplan, Yusuf [Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2013-12-15

    Dynamic phase diagrams are presented for the kinetic spin-3/2 Blume–Capel model under a time oscillating longitudinal field by use of the effective-field theory with correlations. The dynamic equation of the average magnetization is obtained for the square lattice by utilizing the Glauber-type stochastic process. Dynamic phase diagrams are presented in the reduced temperature and the magnetic field amplitude plane. We also investigated the effect of longitudinal field frequency. Finally, the discussion and comparison of the phase diagrams are given. - Highlights: • Dynamic behaviors in the spin-3/2 Blume–Capel system is investigated by the effective-field theory based on the Glauber-type stochastic dynamics. • The dynamic phase transitions and dynamic phase diagrams are obtained. • The effects of the longitudinal field frequency on the dynamic phase diagrams of the system are investigated. • Dynamic phase diagrams exhibit several ordered phases, coexistence phase regions and several critical points as well as a re-entrant behavior.

  5. Effective-field theory for dynamic phase diagrams of the kinetic spin-3/2 Blume–Capel model under a time oscillating longitudinal field

    International Nuclear Information System (INIS)

    Ertaş, Mehmet; Kocakaplan, Yusuf; Keskin, Mustafa

    2013-01-01

    Dynamic phase diagrams are presented for the kinetic spin-3/2 Blume–Capel model under a time oscillating longitudinal field by use of the effective-field theory with correlations. The dynamic equation of the average magnetization is obtained for the square lattice by utilizing the Glauber-type stochastic process. Dynamic phase diagrams are presented in the reduced temperature and the magnetic field amplitude plane. We also investigated the effect of longitudinal field frequency. Finally, the discussion and comparison of the phase diagrams are given. - Highlights: • Dynamic behaviors in the spin-3/2 Blume–Capel system is investigated by the effective-field theory based on the Glauber-type stochastic dynamics. • The dynamic phase transitions and dynamic phase diagrams are obtained. • The effects of the longitudinal field frequency on the dynamic phase diagrams of the system are investigated. • Dynamic phase diagrams exhibit several ordered phases, coexistence phase regions and several critical points as well as a re-entrant behavior

  6. Dynamical mechanism of symmetry breaking and particle mass generation in gauge field theories

    International Nuclear Information System (INIS)

    Miranskij, V.A.; Fomin, P.I.

    1985-01-01

    The dynamics of the spotaneous symmetry breaking and the particle mass generation in gauge theories with no fundamental scalar fields is considered. The emphasis is on the consideration of the symmetry breaking mechanism connected with the dynamics of the supercritical Coulomb-like forces caused by the gauge boson exchange between fermions. This mechanism is applied to different gauge theories, in particular, to the description of the spontaneous chira symmetry breaking in quantum chromodynamics. The mass relations for pseudoscalar meson nonet are obtained and it is shown that this mechanism resuls in the dynamical realisation of the hypothesis of the partial conservation of the axial-vector currents. The qualitative description of scalar mesons is given. The nature of the ultraviolet divergencies in quantum electrodynamics (QED) is investigated from the viewpoint of the dynamics of the fermion mass generation. The mechanism of the appearance of the additional (in comparison with perturbation theory) ultraviolet divergencies in QED with large bare coupling constant is indicated. The physical phenomenon underlying this mechanism is identified as the field theory analogue of the quantum mechanical ''fall into the centre'' (collapse) phenomenon. The similr phenomenon is shown to take place in some two-dimensional quantum field models. The dynamics of the bifermion condensates formation in tumblin gauge theories is briefly discussed

  7. A thermodynamically consistent phenomenological model for ferroelectric and ferroelastic hysteresis

    Czech Academy of Sciences Publication Activity Database

    Kaltenbacher, B.; Krejčí, Pavel

    2016-01-01

    Roč. 96, č. 7 (2016), s. 874-891 ISSN 0044-2267 R&D Projects: GA ČR(CZ) GA15-12227S Institutional support: RVO:67985840 Keywords : piezoelectric ity * hysteresis * ferroelasticity Subject RIV: BA - General Mathematics Impact factor: 1.332, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/zamm.201400292/abstract

  8. Contact angle hysteresis of liquid drops as means to measure ...

    Indian Academy of Sciences (India)

    A comparison of the two methods shows that the extent of contact angle hysteresis is indicative of both hydrophobicity of the surface as well as the force of adhesion. Mechanical properties and microstructure of zein films prepared by casting from solutions and using Langmuir-Blodgett film technique have been investigated.

  9. The back transition and hysteresis effects in DIII-D

    International Nuclear Information System (INIS)

    Thomas, D.M.; Groebner, R.J.; Burrell, K.H.; Osborne, T.H.; Carlstrom, T.N.

    1997-09-01

    The back transition from H-mode to L-mode has been studied on DIII-D as a part of the investigation of the L-H transition power threshold scaling. Based on a density-dependent scaling for the H-mode power threshold, ITER will require substantial hysteresis in this parameter to remain in H-mode as n e rises. Defining the hysteresis in terms of the ratio of sustaining to threshold power, P HL /P LH may need to be as small as 50% for ITER. Operation of DIII-D at injection powers slightly above the H-mode threshold results in an oscillatory behavior with multiple forward-backward transitions in the course of a discharge. These discharges represent a unique system for studying various control parameters that may influence the H↔L state transition. Careful analysis of the power flow through the edge gives values for the sustaining power which are well below the corresponding threshold powers (P HL /P LH = 35--70%), indicating substantial hysteresis can be achieved in this parameter. Studies of other control parameter candidates such as edge temperature during the back transitions are less clear: the amount of hysteresis seen in these parameters, if any, is primarily dependent on the nature (ELMing, ELM-free) of the parent H-state

  10. Improving the performance of hysteresis direct torque control of ...

    Indian Academy of Sciences (India)

    This paper describes an active filter topology to improve the performance of hysteresis direct torque control (HDTC) of interior permanent magnet synchronous motor (IPMSM). The filter topology consists of an active filter and two RLC filters, and is connected to the main power circuit through a 1:1 transformer. The active filter ...

  11. Interpreting diel hysteresis between soil respiration and temperature

    Science.gov (United States)

    C. Phillips; N. Nickerson; D. Risk; B.J. Bond

    2011-01-01

    Increasing use of automated soil respiration chambers in recent years has demonstrated complex diel relationships between soil respiration and temperature that are not apparent from less frequent measurements. Soil surface flux is often lagged from soil temperature by several hours, which results in semielliptical hysteresis loops when surface flux is plotted as a...

  12. Hysteresis in the solid oxide fuel cell cathode reaction

    DEFF Research Database (Denmark)

    Jacobsen, Torben; Zachau-Christiansen, Birgit; Bay, Lasse

    2001-01-01

    The oxygen electrode reaction at the Pt/yttria-stabilised zirconia (YSZ) interface is investigated at 1000degreesC on Pt point electrodes on YSZ and YSZ point contacts on Pt. Linear potential sweeps show a pronounced non-linear current-voltage relation and inductive hysteresis, in particular at l...

  13. A thermodynamically consistent phenomenological model for ferroelectric and ferroelastic hysteresis

    Czech Academy of Sciences Publication Activity Database

    Kaltenbacher, B.; Krejčí, Pavel

    2016-01-01

    Roč. 96, č. 7 (2016), s. 874-891 ISSN 0044-2267 R&D Projects: GA ČR(CZ) GA15-12227S Institutional support: RVO:67985840 Keywords : piezoelectricity * hysteresis * ferroelasticity Subject RIV: BA - General Mathematics Impact factor: 1.332, year: 2016 http://onlinelibrary.wiley.com/doi/10.1002/zamm.201400292/abstract

  14. Hysteresis of soil temperature under different soil moisture and ...

    African Journals Online (AJOL)

    ... in a solar greenhouse. The objective of this study was to find a simple method to estimate the hysteresis of soil temperature under three soil moisture and two fertilizer levels in solar greenhouse conditions with tomato crop (Lycopersicon esculentum Mill). The results show that the soil moisture had no significant effects on ...

  15. Hysteresis Control for a DC Connected Synchronous Generator

    DEFF Research Database (Denmark)

    Rasmussen, Tonny Wederberg; Evangelos, Dimarakis

    2009-01-01

    Abstract— for offshore wind farms the distance to the coast increases, therefore DC cables will have to be used. For a variable speed wind turbine a rectifier and a synchronous generator with a boost converter is used. As a new suggestion for control the generator speed hysteresis control...

  16. Non-Linear Dynamics of a Porous Medium Saturated With Electrolyte in the Magnetic Field

    Science.gov (United States)

    Perepechko, Y.

    2006-12-01

    The correct description of dynamics of saturated porous media in the magnetic field is one of the topical problems for mechanics of electromagnetic multi-phase media. This report studies the non-linear model of the conducting liquid flow through non-conducting deformable porous medium in the external magnetic field. We consider the most interesting case with the magnetic field, transverse to the fluid flow, what allows us to examine interaction between the magnetic field and transverse oscillations. The determining equations of the model, including non-linear two-velocity equations for dynamics of saturated porous deformable medium and Maxwell equation in magnetic-hydrodynamic approximation, are invariant relative to Galileo transformation and coordinated from the point of thermal dynamics. This model includes two longitudinal types of acoustic waves and two transverse types of magnetic-acoustic waves, which are transformed into transverse sound-waves and Alfven waves without magnetic-acoustic interaction. The effect of external magnetic field on the pattern of non- linear filtration of electrolyte through an inelastically-deformable porous medium is studied numerically together with the analysis of coordinated magnetic fields, generated during electrolyte filtration and porous matrix deformation. An increase in the magnetic field by a liquid conducting phase is examined in two cases: for the trapped magnetic field and for diffusion of the magnetic field due to electric conductivity of electrolyte. This model allows investigation of magnetic-seismic and seismic-magnetic effects and their use in applied geophysics, particularly, for earthquake forecast and development of new methods for geophysical research. This research was supported by the Russian Foundation for Basic Research grant 06.05.65110, by the President's grants NSh.1573.2003.5, and by the Russian Ministry Science and Education grant RNP.2.1.1.702.

  17. Filling the Gap on Developmental Change: Tests of a Dynamic Field Theory of Spatial Cognition

    Science.gov (United States)

    Schutte, Anne R.; Spencer, John P.

    2010-01-01

    In early childhood, there is a developmental transition in spatial memory biases. Before the transition, children's memory responses are biased toward the midline of a space, while after the transition responses are biased away from midline. The Dynamic Field Theory (DFT) posits that changes in neural interaction and changes in how children…

  18. Automating the mean-field method for large dynamic gossip networks

    NARCIS (Netherlands)

    Bakhshi, Rena; Endrullis, Jörg; Endrullis, Stefan; Fokkink, Wan; Haverkort, Boudewijn R.H.M.

    We investigate an abstraction method, called mean- field method, for the performance evaluation of dynamic net- works with pairwise communication between nodes. It allows us to evaluate systems with very large numbers of nodes, that is, systems of a size where traditional performance evaluation

  19. A Dynamic BI–Orthogonal Field Equation Approach to Efficient Bayesian Inversion

    Directory of Open Access Journals (Sweden)

    Tagade Piyush M.

    2017-06-01

    Full Text Available This paper proposes a novel computationally efficient stochastic spectral projection based approach to Bayesian inversion of a computer simulator with high dimensional parametric and model structure uncertainty. The proposed method is based on the decomposition of the solution into its mean and a random field using a generic Karhunen-Loève expansion. The random field is represented as a convolution of separable Hilbert spaces in stochastic and spatial dimensions that are spectrally represented using respective orthogonal bases. In particular, the present paper investigates generalized polynomial chaos bases for the stochastic dimension and eigenfunction bases for the spatial dimension. Dynamic orthogonality is used to derive closed-form equations for the time evolution of mean, spatial and the stochastic fields. The resultant system of equations consists of a partial differential equation (PDE that defines the dynamic evolution of the mean, a set of PDEs to define the time evolution of eigenfunction bases, while a set of ordinary differential equations (ODEs define dynamics of the stochastic field. This system of dynamic evolution equations efficiently propagates the prior parametric uncertainty to the system response. The resulting bi-orthogonal expansion of the system response is used to reformulate the Bayesian inference for efficient exploration of the posterior distribution. The efficacy of the proposed method is investigated for calibration of a 2D transient diffusion simulator with an uncertain source location and diffusivity. The computational efficiency of the method is demonstrated against a Monte Carlo method and a generalized polynomial chaos approach.

  20. Dynamical mean-field approach to materials with strong electronic correlations

    Czech Academy of Sciences Publication Activity Database

    Kuneš, Jan; Leonov, I.; Kollar, M.; Byczuk, K.; Anisimov, V.I.; Vollhardt, D.

    2010-01-01

    Roč. 180, - (2010), s. 5-28 ISSN 1951-6355 Institutional research plan: CEZ:AV0Z10100521 Keywords : dynamical mean-field * electronic correlations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.838, year: 2010

  1. Field-based dynamic light scattering microscopy: theory and numerical analysis

    NARCIS (Netherlands)

    Joo, C.; de Boer, J.F.

    2013-01-01

    We present a theoretical framework for field-based dynamic light scattering microscopy based on a spectral-domain optical coherence phase microscopy (SD-OCPM) platform. SD-OCPM is an interferometric microscope capable of quantitative measurement of amplitude and phase of scattered light with high

  2. A molecular dynamics algorithm for simulation of field theories in the canonical ensemble

    International Nuclear Information System (INIS)

    Kogut, J.B.; Sinclair, D.K.

    1986-01-01

    We add a single scalar degree of freedom (''demon'') to the microcanonical ensemble which converts its molecular dynamics into a simulation method for the canonical ensemble (euclidean path integral) of the underlying field theory. This generalization of the microcanonical molecular dynamics algorithm simulates the field theory at fixed coupling with a completely deterministic procedure. We discuss the finite size effects of the method, the equipartition theorem and ergodicity. The method is applied to the planar model in two dimensions and SU(3) lattice gauge theory with four species of light, dynamical quarks in four dimensions. The method is much less sensitive to its discrete time step than conventional Langevin equation simulations of the canonical ensemble. The method is a straightforward generalization of a procedure introduced by S. Nose for molecular physics. (orig.)

  3. Lorentz-Violating Regulator Gauge Fields as the Origin of Dynamical Flavour Oscillations

    CERN Document Server

    Alexandre, Jean; Mavromatos, Nick E

    2013-01-01

    We show how a mass mixing matrix can be generated dynamically, for two massless fermion flavours coupled to a Lorentz invariance violating (LIV) gauge field. The LIV features play the role of a regulator for the gap equations, and the non-analytic dependence of the dynamical masses, as functions of the gauge coupling, allows to consider the limit where the LIV gauge field eventually decouples from the fermions. Lorentz invariance is then recovered, to describe the oscillation between two free fermion flavours, and we check that the finite dynamical masses are the only effects of the original LIV theory. We also discuss briefly a connection of our results with the case of Majorana neutrinos in both, the standard model, where only left-handed (active) neutrinos are considered, and extensions thereof, with sterile right-handed neutrinos.

  4. Dynamic Time Warping Distance Method for Similarity Test of Multipoint Ground Motion Field

    Directory of Open Access Journals (Sweden)

    Yingmin Li

    2010-01-01

    Full Text Available The reasonability of artificial multi-point ground motions and the identification of abnormal records in seismic array observations, are two important issues in application and analysis of multi-point ground motion fields. Based on the dynamic time warping (DTW distance method, this paper discusses the application of similarity measurement in the similarity analysis of simulated multi-point ground motions and the actual seismic array records. Analysis results show that the DTW distance method not only can quantitatively reflect the similarity of simulated ground motion field, but also offers advantages in clustering analysis and singularity recognition of actual multi-point ground motion field.

  5. Brief communication "Modeling tornado dynamics and the generation of infrasound, electric and magnetic fields"

    Directory of Open Access Journals (Sweden)

    E. D. Schmitter

    2010-02-01

    Full Text Available Recent observations endorse earlier measurements of time varying electric and magnetic fields generated by tornadoes and dust devils. These signals may provide a means for early warning but together with a proper modeling approach can also provide insight into geometry and dynamics of the vortices. Our model calculations show the existence of pressure resonances characterized as acoustic duct modes with well defined frequencies. These resonances not only generate infrasound but also modulate the charge density and the velocity field and in this way lead to electric and magnetic field oscillations in the 0.5–20-Hz range that can be monitored from a distance of several kilometers.

  6. Nonequilibrium dynamical renormalization group: Dynamical crossover from weak to infinite randomness in the transverse-field Ising chain

    Science.gov (United States)

    Heyl, Markus; Vojta, Matthias

    2015-09-01

    In this work we formulate the nonequilibrium dynamical renormalization group (ndRG). The ndRG represents a general renormalization-group scheme for the analytical description of the real-time dynamics of complex quantum many-body systems. In particular, the ndRG incorporates time as an additional scale which turns out to be important for the description of the long-time dynamics. It can be applied to both translational-invariant and disordered systems. As a concrete application, we study the real-time dynamics after a quench between two quantum critical points of different universality classes. We achieve this by switching on weak disorder in a one-dimensional transverse-field Ising model initially prepared at its clean quantum critical point. By comparing to numerically exact simulations for large systems, we show that the ndRG is capable of analytically capturing the full crossover from weak to infinite randomness. We analytically study signatures of localization in both real space and Fock space.

  7. Pulse propagation dynamics in the presence of a continuous-wave field

    International Nuclear Information System (INIS)

    Dimitrijević, Jelena; Arsenović, Dušan; Jelenković, Branislav M

    2013-01-01

    We present theoretical results for the propagation dynamics of an electromagnetic field pulse through rubidium vapor, while another field, a continuous-wave electromagnetic field, is present. The frequencies of both electromagnetic fields are resonant with the transition between the ground and excited state hyperfine levels of Rb, F g  → F e  = F g  ± 1. Detuning from resonance is done by the magnetic field oriented along the light propagation direction (Hanle configuration). When both the electromagnetic fields are simultaneously interacting with Rb atoms, either electromagnetically induced transparency or absorption is induced. Propagation dynamics was obtained solving the set of Maxwell–Bloch equations for the interacting atoms with two electromagnetic fields. Motivated by recent results (Brazhnikov et al 2011 Eur. Phys. J. D 63 315–25; Brazhnikov et al 2010 JETP Lett. 91 625–9; Kou et al 2011 Phys. Rev. A 84 063807), we have analyzed the influence of experimental parameters, laser polarization, and mutual phases between lasers, which can lead to optical switching, i.e. the transformation from electromagnetically induced absorption to transparency and vice versa. (paper)

  8. Hole dynamics and spin currents after ionization in strong circularly polarized laser fields

    International Nuclear Information System (INIS)

    Barth, Ingo; Smirnova, Olga

    2014-01-01

    We apply the time-dependent analytical R-matrix theory to develop a movie of hole motion in a Kr atom upon ionization by strong circularly polarized field. We find rich hole dynamics, ranging from rotation to swinging motion. The motion of the hole depends on the final energy and the spin of the photoelectron and can be controlled by the laser frequency and intensity. Crucially, hole rotation is a purely non-adiabatic effect, completely missing in the framework of quasistatic (adiabatic) tunneling theories. We explore the possibility to use hole rotation as a clock for measuring ionization time. Analyzing the relationship between the relative phases in different ionization channels we show that in the case of short-range electron-core interaction the hole is always initially aligned along the instantaneous direction of the laser field, signifying zero delays in ionization. Finally, we show that strong-field ionization in circular fields creates spin currents (i.e. different flow of spin-up and spin-down density in space) in the ions. This phenomenon is intimately related to the production of spin-polarized electrons in strong laser fields Barth and Smirnova (2013 Phys. Rev. A 88 013401). We demonstrate that rich spin dynamics of electrons and holes produced during strong field ionization can occur in typical experimental conditions and does not require relativistic intensities or strong magnetic fields. (paper)

  9. Influence of periodic external fields in multiagent models with language dynamics

    Science.gov (United States)

    Palombi, Filippo; Ferriani, Stefano; Toti, Simona

    2017-12-01

    We investigate large-scale effects induced by external fields, phenomenologically interpreted as mass media, in multiagent models evolving with the microscopic dynamics of the binary naming game. In particular, we show that a single external field, broadcasting information at regular time intervals, can reverse the majority opinion of the population, provided the frequency and the effectiveness of the sent messages lie above well-defined thresholds. We study the phase structure of the model in the mean field approximation and in numerical simulations with several network topologies. We also investigate the influence on the agent dynamics of two competing external fields, periodically broadcasting different messages. In finite regions of the parameter space we observe periodic equilibrium states in which the average opinion densities are reversed with respect to naive expectations. Such equilibria occur in two cases: (i) when the frequencies of the competing messages are different but close to each other; (ii) when the frequencies are equal and the relative time shift of the messages does not exceed half a period. We interpret the observed phenomena as a result of the interplay between the external fields and the internal dynamics of the agents and conclude that, depending on the model parameters, the naming game is consistent with scenarios of first- or second-mover advantage (to borrow an expression from the jargon of business strategy).

  10. Dynamic rheological properties of viscoelastic magnetic fluids in uniform magnetic fields

    International Nuclear Information System (INIS)

    Yamaguchi, Hiroshi; Niu Xiaodong; Ye Xiaojiang; Li Mingjun; Iwamoto, Yuhiro

    2012-01-01

    The dynamic rheological properties of viscoelastic magnetic fluids in externally applied uniform magnetic fields are investigated by a laboratory-made cone-plate rheometer in this study. In particular, the effects of the magnetic field on the viscoelastic properties (the complex dynamic modulus) of the viscoelastic magnetic fluids are studied. In the investigation, three viscoelastic magnetic fluids are made by mixing a magnetic fluid and a viscoelastic fluid with different mass ratios. As a supplementation to the experimental investigation, a theoretical analysis is also presented. The present study shows that the viscosity and elasticity of the viscoelastic magnetic fluids are significantly influenced by the magnetic field and the concentrations of the magnetic particles in the test fluids. Theoretical analysis qualitatively explains the present findings. - Highlights: ► The dynamic rheological properties of the viscoelastic magnetic fluids in uniform magnetic fields are investigated. ► Both the magnetic field strength and the concentration of the magnetic particles in the fluids have significant effects on the viscosity and elasticity of the viscoelastic magnetic fluids. ► Theoretical prediction and analysis qualitatively explains the present findings.

  11. THE EFFECT OF MAGNETIC FIELD ERRORS ON DYNAMICAL FRICTION IN ELECTRON COOLERS.

    Energy Technology Data Exchange (ETDEWEB)

    FEDOTOV, A.V.; LITVINENKO, V.N.

    2005-05-16

    A proposed luminosity upgrade to the Relativistic Heavy Ion Collider (RHIC) includes a novel electron cooling section [1], which would use -55 MeV electrons to cool fully-ionized 100 GeV/nucleon gold ions. A strong (1-5 T) solenoidal field will be used to magnetize the electrons and thus enhance the dynamical friction force on the ions. The physics of magnetized friction is being simulated for RHIC parameters [2,3,4], using the VORPAL code [5]. Most theoretical treatments for magnetized dynamical friction do not consider the effect of magnetic field errors, except in a parametric fashion. However, field errors can in some cases dramatically reduce the velocity drag and corresponding cooling rate. We present two simple analytical models for the magnetic field errors. The simulated dynamical friction for the case of a perfect solenoidal field is compared with results from these new models. We simulate parameters for the existing cooler of the CELSIUS ring, because recent experiments [6] provide data that will later be used for code validation.

  12. Dynamics of Entanglement in Jaynes–Cummings Nodes with Nonidentical Qubit-Field Coupling Strengths

    Directory of Open Access Journals (Sweden)

    Li-Tuo Shen

    2017-07-01

    Full Text Available How to analytically deal with the general entanglement dynamics of separate Jaynes–Cummings nodes with continuous-variable fields is still an open question, and few analytical approaches can be used to solve their general entanglement dynamics. Entanglement dynamics between two separate Jaynes–Cummings nodes are examined in this article. Both vacuum state and coherent state in the initial fields are considered through the numerical and analytical methods. The gap between two nonidentical qubit-field coupling strengths shifts the revival period and changes the revival amplitude of two-qubit entanglement. For vacuum-state fields, the maximal entanglement is fully revived after a gap-dependence period, within which the entanglement nonsmoothly decreases to zero and partly recovers without exhibiting sudden death phenomenon. For strong coherent-state fields, the two-qubit entanglement decays exponentially as the evolution time increases, exhibiting sudden death phenomenon, and the increasing gap accelerates the revival period and amplitude decay of the entanglement, where the numerical and analytical results have an excellent coincidence.

  13. Hysteresis controller with constant switching frequency

    DEFF Research Database (Denmark)

    Poulsen, Søren; Andersen, Michael Andreas E.

    2005-01-01

    Switch mode audio power amplifiers are showing up on market in still greater numbers because of advantages in form of high efficiency and low total system cost, especially for high power amplifiers. Several different modulator topologies have been made, ranging from standard PWM to various self......-oscillating and digital modulators. Performance in terms of low distortion, noise and dynamic range differs significantly with the modulator topology used. Highest system performance is generally achieved with analog modulators made as a modulator loop including at least the power stage of the amplifier, because...... of benefits from continuous time operation and non-quantized resolution. This type of modulator uses no external carrier signal, and is called self-oscillating modulators. The work presented in this paper refers to switch mode audio power amplifier, but can be used within a wide range of DC-DC or DC...

  14. Determination of Quantum Chemistry Based Force Fields for Molecular Dynamics Simulations of Aromatic Polymers

    Science.gov (United States)

    Jaffe, Richard; Langhoff, Stephen R. (Technical Monitor)

    1995-01-01

    Ab initio quantum chemistry calculations for model molecules can be used to parameterize force fields for molecular dynamics simulations of polymers. Emphasis in our research group is on using quantum chemistry-based force fields for molecular dynamics simulations of organic polymers in the melt and glassy states, but the methodology is applicable to simulations of small molecules, multicomponent systems and solutions. Special attention is paid to deriving reliable descriptions of the non-bonded and electrostatic interactions. Several procedures have been developed for deriving and calibrating these parameters. Our force fields for aromatic polyimide simulations will be described. In this application, the intermolecular interactions are the critical factor in determining many properties of the polymer (including its color).

  15. Influence of external fields and environment on the dynamics of a phase-qubit-resonator system

    International Nuclear Information System (INIS)

    Berman, G. P.; Chumak, A. A.

    2011-01-01

    We analyze the dynamics of a qubit-resonator system coupled with a thermal bath and external electromagnetic fields. Using the evolution equations for the set of Heisenberg operators that describe the whole system, we derive an expression for the resonator field, accounting for the resonator-drive, -bath, and -qubit interaction. The renormalization of the resonator frequency caused by the qubit-resonator interaction is accounted for. Using solutions for the resonator field, we derive the equation describing qubit dynamics. The influence of the qubit evolution during measurement time on the fidelity of a single-shot measurement is studied. The relation between fidelity and measurement time is shown explicitly. Also, an expression describing relaxation of the superposition qubit state toward its stationary value is derived. The possibility of controlling this state by varying the amplitude and frequency of drive is shown.

  16. Modelling capillary hysteresis effects on preferential flow through melting and cold layered snowpacks

    Science.gov (United States)

    Leroux, Nicolas R.; Pomeroy, John W.

    2017-09-01

    Accurate estimation of the amount and timing of water flux through melting snowpacks is important for runoff prediction in cold regions. Most existing snowmelt models only account for one-dimensional matrix flow and neglect to simulate the formation of preferential flow paths. Consideration of lateral and preferential flows has proven critical to improve the performance of soil and groundwater porous media flow models. A two-dimensional physically-based snowpack model that simulates snowmelt, refreezing of meltwater, heat and water flows, and preferential flow paths is presented. The model assumes thermal equilibrium between solid and liquid phases and uses recent snow physics advances to estimate snowpack hydraulic and thermal properties. For the first time, capillary hysteresis is accounted in a snowmelt model. A finite volume method is applied to solve for the 2D coupled heat and mass transfer equations. The model with capillary hysteresis provided better simulations of water suction at the wet to dry snow interface in a wetting snow sample than did a model that only accounted for the boundary drying curve. Capillary hysteresis also improved simulations of preferential flow path dynamics and the snowpack discharge hydrograph. Simulating preferential flow in a subfreezing snowpack allowed the model to generate ice layers, and increased the vertical exchange of energy, thus modelling a faster warming of the snowpack than would be possible without preferential flow. The model is thus capable of simulating many attributes of heterogeneous natural melting snowpacks. These features not only qualitatively improve water flow simulations, but improve the understanding of snowmelt flow processes for both level and sloping terrain, and illuminate how uncertainty in snowmelt-derived runoff calculations might be reduced through the inclusion of more realistic preferential flow through snowpacks.

  17. Classical study of the rovibrational dynamics of a polar diatomic molecule in static electric fields

    Energy Technology Data Exchange (ETDEWEB)

    Inarrea, Manuel, E-mail: manuel.inarrea@unirioja.e [Area de Fisica, Universidad de la Rioja, E-26006 Logrono (Spain); Salas, J. Pablo [Area de Fisica, Universidad de la Rioja, E-26006 Logrono (Spain); Gonzalez-Ferez, Rosario [Instituto ' Carlos I' de Fisica Teorica y Computacional, Universidad de Granada, E-18071 Granada (Spain); Departamento de Fisica Atomica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain); Schmelcher, Peter [Theoretische Chemie, Physikalisch-Chemisches Institut, D-69120 Heidelberg (Germany); Physikalisches Institut, Universitaet Heidelberg, D-69120 Heidelberg (Germany)

    2010-01-04

    We study the classical dynamics of a polar diatomic molecule in the presence of a strong static homogeneous electric field. Our full rovibrational investigation includes the interaction with the field due to the permanent electric dipole moment and the polarizability of the molecule. Using the LiCs molecule as a prototype, we explore the stability of the equilibrium points and their bifurcations as the field strength is increased. The phase space structure and its dependence on the energy and field strength are analyzed in detail. We demonstrate that depending on the field strength and on the energy, the phase space is characterized either by regular features or by small stochastic layers of chaotic motion.

  18. Effects of seed magnetic fields on magnetohydrodynamic implosion structure and dynamics

    KAUST Repository

    Mostert, W.

    2014-12-01

    The effects of various seed magnetic fields on the dynamics of cylindrical and spherical implosions in ideal magnetohydrodynamics are investigated. Here, we present a fundamental investigation of this problem utilizing cylindrical and spherical Riemann problems under three seed field configurations to initialize the implosions. The resulting flows are simulated numerically, revealing rich flow structures, including multiple families of magnetohydrodynamic shocks and rarefactions that interact non-linearly. We fully characterize these flow structures, examine their axi- and spherisymmetry-breaking behaviour, and provide data on asymmetry evolution for different field strengths and driving pressures for each seed field configuration. We find that out of the configurations investigated, a seed field for which the implosion centre is a saddle point in at least one plane exhibits the least degree of asymmetry during implosion.

  19. Molecular dynamics simulation of the response of bi-disperse polyelectrolyte brushes to external electric fields

    International Nuclear Information System (INIS)

    Zhang Fen; Ding Huan-Da; Duan Chao; Tong Chao-Hui; Zhao Shuang-Liang

    2017-01-01

    Langevin dynamics simulations have been performed to investigate the response of bi-disperse and strong polyacid chains grafted on an electrode to electric fields generated by opposite surface charges on the polyelectrolyte (PE)-grafted electrode and a second parallel electrode. Simulation results clearly show that, under a negative external electric field, the longer grafted PE chains are more strongly stretched than the shorter ones in terms of the relative change in their respective brush heights. Whereas under a positive external electric field, the grafted shorter chains collapse more significantly than the longer ones. It was found that, under a positive external electric field, the magnitude of the total electric force acting on one shorter PE chain is larger than that on one longer PE chain, or vice versa. The effects of smeared and discrete charge distributions of grafted PE chains on the response of PE brushes to external electric fields were also examined. (paper)

  20. Velocity map imaging of scattering dynamics in orthogonal two-color fields

    Science.gov (United States)

    Würzler, D.; Eicke, N.; Möller, M.; Seipt, D.; Sayler, A. M.; Fritzsche, S.; Lein, M.; Paulus, G. G.

    2018-01-01

    In strong-field ionization processes, two-color laser fields are frequently used for controlling sub-cycle electron dynamics via the relative phase of the laser fields. Here we apply this technique to velocity map imaging spectroscopy using an unconventional orientation with the polarization of the ionizing laser field perpendicular to the detector surface and the steering field parallel to it. This geometry allows not only to image the phase-dependent photoelectron momentum distribution (PMD) of low-energy electrons that interact only weakly with the ion (direct electrons), but also to investigate the low yield of higher-energy rescattered electrons. Phase-dependent measurements of the PMD of neon and xenon demonstrate control over direct and rescattered electrons. The results are compared with semi-classical calculations in three dimensions including elastic scattering at different orders of return and with solutions of the three-dimensional time-dependent Schrödinger equation.

  1. Error Propagation dynamics: from PIV-based pressure reconstruction to vorticity field calculation

    Science.gov (United States)

    Pan, Zhao; Whitehead, Jared; Richards, Geordie; Truscott, Tadd; USU Team; BYU Team

    2017-11-01

    Noninvasive data from velocimetry experiments (e.g., PIV) have been used to calculate vorticity and pressure fields. However, the noise, error, or uncertainties in the PIV measurements would eventually propagate to the calculated pressure or vorticity field through reconstruction schemes. Despite the vast applications of pressure and/or vorticity field calculated from PIV measurements, studies on the error propagation from the velocity field to the reconstructed fields (PIV-pressure and PIV-vorticity are few. In the current study, we break down the inherent connections between PIV-based pressure reconstruction and PIV-based vorticity calculation. The similar error propagation dynamics, which involve competition between physical properties of the flow and numerical errors from reconstruction schemes, are found in both PIV-pressure and PIV-vorticity reconstructions.

  2. Magnetic hysteresis of an artificial square ice studied by in-plane Bragg x-ray resonant magnetic scattering

    Directory of Open Access Journals (Sweden)

    J. P. Morgan

    2012-06-01

    Full Text Available We report X-ray resonant magnetic scattering studies of a Permalloy artificial square ice nanomagnet array, focussing on the field-driven evolution of the sum Σ and difference Δ signals of left and right handed circularly polarized synchrotron X-rays at different lateral positions in reciprocal space Qx. We used X-rays tuned to the Fe L3 resonance energy, with the scattering plane aligned along a principal symmetry axis of the array. Details of the specular Δ hysteresis curve are discussed, following the system magnetization from an initial demagnetized state. The periodic structure gives rise to distinct peaks at in-plane reciprocal Bragg positions, as shown by fitting Σ(Qx to a model based on a simple unit cell structure. Diffraction order-dependent hysteresis in Δ is observed, indicative of the reordering of magnetization on the system's two interpenetrating sublattices, which markedly deviates from an ideal Ising picture under strong applied fields.

  3. Monte Carlo simulations of phase transitions and lattice dynamics in an atom-phonon model for spin transition compounds

    International Nuclear Information System (INIS)

    Apetrei, Alin Marian; Enachescu, Cristian; Tanasa, Radu; Stoleriu, Laurentiu; Stancu, Alexandru

    2010-01-01

    We apply here the Monte Carlo Metropolis method to a known atom-phonon coupling model for 1D spin transition compounds (STC). These inorganic molecular systems can switch under thermal or optical excitation, between two states in thermodynamical competition, i.e. high spin (HS) and low spin (LS). In the model, the ST units (molecules) are linked by springs, whose elastic constants depend on the spin states of the neighboring atoms, and can only have three possible values. Several previous analytical papers considered a unique average value for the elastic constants (mean-field approximation) and obtained phase diagrams and thermal hysteresis loops. Recently, Monte Carlo simulation papers, taking into account all three values of the elastic constants, obtained thermal hysteresis loops, but no phase diagrams. Employing Monte Carlo simulation, in this work we obtain the phase diagram at T=0 K, which is fully consistent with earlier analytical work; however it is more complex. The main difference is the existence of two supplementary critical curves that mark a hysteresis zone in the phase diagram. This explains the pressure hysteresis curves at low temperature observed experimentally and predicts a 'chemical' hysteresis in STC at very low temperatures. The formation and the dynamics of the domains are also discussed.

  4. Research of Jiles-Atherton Dynamic Model in Giant Magnetostrictive Actuator

    Directory of Open Access Journals (Sweden)

    Yongguang Liu

    2016-01-01

    Full Text Available Due to the existence of multicoupled nonlinear factors in the giant magnetostrictive actuator (GMA, building precise mathematical model is highly important to study GMA’s characteristics and control strategies. Minor hysteresis loops near the bias magnetic field would be often applied because of its relatively good linearity. Load, friction, and disc spring stiffness seriously affect the output characteristics of the GMA in high frequency. Therefore, the current-displacement dynamic minor loops mathematical model coupling of electric-magnetic-machine is established according to Jiles-Atherton (J-A dynamic model of hysteresis material, GMA structural dynamic equation, Ampere loop circuit law, and nonlinear piezomagnetic equation and demonstrates its correctness and effectiveness in the experiments. Finally, some laws are achieved between key structural parameters and output characteristics of GMA, which provides important theoretical foundation for structural design.

  5. A Database of Force-Field Parameters, Dynamics, and Properties of Antimicrobial Compounds

    Directory of Open Access Journals (Sweden)

    Giuliano Malloci

    2015-08-01

    Full Text Available We present an on-line database of all-atom force-field parameters and molecular properties of compounds with antimicrobial activity (mostly antibiotics and some beta-lactamase inhibitors. For each compound, we provide the General Amber Force Field parameters for the major species at physiological pH, together with an analysis of properties of interest as extracted from µs-long molecular dynamics simulations in explicit water solution. The properties include number and population of structural clusters, molecular flexibility, hydrophobic and hydrophilic molecular surfaces, the statistics of intraand inter-molecular H-bonds, as well as structural and dynamical properties of solvent molecules within first and second solvation shells. In addition, the database contains several key molecular parameters, such as energy of the frontier molecular orbitals, vibrational properties, rotational constants, atomic partial charges and electric dipole moment, computed by Density Functional Theory. The present database (to our knowledge the first extensive one including dynamical properties is part of a wider project aiming to build-up a database containing structural, physico-chemical and dynamical properties of medicinal compounds using different force-field parameters with increasing level of complexity and reliability. The database is freely accessible at http://www.dsf.unica.it/translocation/db/.

  6. [Geostatistical analysis on distribution dynamics of Myzus persicae (Sulzer) in flue-cured tobacco field].

    Science.gov (United States)

    Xia, Peng-liang; Liu, Ying-hong; Fan, Jun; Tan, Jun

    2015-02-01

    Abstract: Myzus persicae belonging to Aphididae, Hemiptera, is an important migratory pest in tobacco field. As nymph and adult, it sucks the juice, breeds the mildew stains disease, spreads tobacco virus diseases and causes huge losses to the yield and quality. The distribution pattern and dynamics of winged and wingless aphids in the field were investigated from the transplanting of tobacco to the harvesting stage of mid-place tobacco leaves in Enshi, Hubei. The semivariable function characteristics were analyzed by geostatistical method, and the field migration pattern were simulated. The results showed that the population dynamics of winged aphids in Enshi were of bimodal curve, with two peaks at 3 weeks after transplanting and 2 weeks after multi-topping of tobacco leaves, and there were five-step process such as random, aggregation, random, aggregation and random. The population dynamics of wingless peach aphids were of single-peak curve, getting its peak before multi-topping, and had random, aggregation, random three-step process. Human factors and the hosts had considerable effects on the population density. Spatial distribution simulation-interpolation-figure could clearly reflect the dynamics of tobacco aphids. Combined with the Pearson correlation analysis, we found that the population density was low and highly concentrated as winged type in the immigration period, which was the key period for the management of peach aphids.

  7. Dynamic chaos in the tunnelling ionization produced by a strong low-frequency electromagnetic field

    International Nuclear Information System (INIS)

    Krainov, V P

    2014-01-01

    Ionization of atoms by a strong low-frequency linearly polarized electromagnetic field (the photon energy is small compared to the atomic ionization potential) is considered under new conditions compared to the well known Keldysh approach. The field strength is supposed to be small in comparison to the atomic field strength. But the Coulomb interaction of an electron with atomic core is assumed to be of the same order of magnitude as the interaction between an electron and the external electromagnetic field. It was shown that then classical electron motion in the continuum becomes chaotic (this is so-called dynamic chaos). Using the averaging procedure of Chirikov about the chaotic variation of the phase of motion, the considered Newton problem is transformed into the problem of nonlinear electron diffusion over energy scale. In this work we derive the classical electron energy averaged over fast chaotic oscillations of an electron in the final continuum state which takes into account both the Coulomb field and electromagnetic field. This energy is used for analytic calculation of the ionization rate of the ground atomic state into the low lying continuum state based on the Landau–Dykhne approximation (with exponential accuracy). We found that the ionization rate depends significantly on the field frequency. When field frequency decreases, the well known tunnelling limit has been obtained, and then the ionization rate does not depend on the field frequency. (paper)

  8. Friction law and hysteresis in granular materials

    Science.gov (United States)

    DeGiuli, E.; Wyart, M.

    2017-08-01

    The macroscopic friction of particulate materials often weakens as the flow rate is increased, leading to potentially disastrous intermittent phenomena including earthquakes and landslides. We theoretically and numerically study this phenomenon in simple granular materials. We show that velocity weakening, corresponding to a nonmonotonic behavior in the friction law, μ(I), is present even if the dynamic and static microscopic friction coefficients are identical, but disappears for softer particles. We argue that this instability is induced by endogenous acoustic noise, which tends to make contacts slide, leading to faster flow and increased noise. We show that soft spots, or excitable regions in the materials, correspond to rolling contacts that are about to slide, whose density is described by a nontrivial exponent θs. We build a microscopic theory for the nonmonotonicity of μ(I), which also predicts the scaling behavior of acoustic noise, the fraction of sliding contacts χ, and the sliding velocity, in terms of θs. Surprisingly, these quantities have no limit when particles become infinitely hard, as confirmed numerically. Our analysis rationalizes previously unexplained observations and makes experimentally testable predictions.

  9. High-Bandwidth Dynamic Full-Field Profilometry for Nano-Scale Characterization of MEMS

    International Nuclear Information System (INIS)

    Chen, L-C; Huang, Y-T; Chang, P-B

    2006-01-01

    The article describes an innovative optical interferometric methodology to delivery dynamic surface profilometry with a measurement bandwidth up to 10MHz or higher and a vertical resolution up to 1 nm. Previous work using stroboscopic microscopic interferometry for dynamic characterization of micro (opto)electromechanical systems (M(O)EMS) has been limited in measurement bandwidth mainly within a couple of MHz. For high resonant mode analysis, the stroboscopic light pulse is insufficiently short to capture the moving fringes from dynamic motion of the detected structure. In view of this need, a microscopic prototype based on white-light stroboscopic interferometry with an innovative light superposition strategy was developed to achieve dynamic full-field profilometry with a high measurement bandwidth up to 10MHz or higher. The system primarily consists of an optical microscope, on which a Mirau interferometric objective embedded with a piezoelectric vertical translator, a high-power LED light module with dual operation modes and light synchronizing electronics unit are integrated. A micro cantilever beam used in AFM was measured to verify the system capability in accurate characterisation of dynamic behaviours of the device. The full-field seventh-mode vibration at a vibratory frequency of 3.7MHz can be fully characterized and nano-scale vertical measurement resolution as well as tens micrometers of vertical measurement range can be performed

  10. Investigating the fluid dynamics of rapid processes within microfluidic devices using bright-field microscopy.

    Science.gov (United States)

    Pirbodaghi, Tohid; Vigolo, Daniele; Akbari, Samin; deMello, Andrew

    2015-05-07

    The widespread application of microfluidic devices in the biological and chemical sciences requires the implementation of complex designs and geometries, which in turn leads to atypical fluid dynamic phenomena. Accordingly, a complete understanding of fluid dynamics in such systems is key in the facile engineering of novel and efficient analytical tools. Herein, we present an accurate approach for studying the fluid dynamics of rapid processes within microfluidic devices using bright-field microscopy with white light illumination and a standard high-speed camera. Specifically, we combine Ghost Particle Velocimetry and the detection of moving objects in automated video surveillance to track submicron size tracing particles via cross correlation between the speckle patterns of successive images. The efficacy of the presented technique is demonstrated by measuring the flow field over a square pillar (80 μm × 80 μm) in a 200 μm wide microchannel at high volumetric flow rates. Experimental results are in excellent agreement with those obtained via computational fluid dynamics simulations. The method is subsequently used to study the dynamics of droplet generation at a flow focusing microfluidic geometry. A unique feature of the presented technique is the ability to perform velocimetry analysis of high-speed phenomena, which is not possible using micron-resolution particle image velocimetry (μPIV) approaches based on confocal or fluorescence microscopy.

  11. Dependence of developing magnetic hysteresis characteristics on stages of evolving microstructure in polycrystalline yttrium iron garnet

    International Nuclear Information System (INIS)

    Rodziah, N.; Hashim, M.; Idza, I.R.; Ismayadi, I.; Hapishah, A.N.; Khamirul, M.A.

    2012-01-01

    The microstructure evolution in several polycrystalline yttrium iron garnet samples as a result of a sintering scheme was studied in detail, in parallel with the changes in their magnetic properties. Samples with nanometer sized starting powder were synthesized by employing the High-Energy Ball Milling technique and then sintering toroidal compacts of the milled powder. Nine sintered samples were obtained, each corresponding to a particular sintering from 600 °C to 1400 °C. The samples were characterized for their evolution in crystalline phases, microstructure and magnetic hysteresis-loops parameters. The results showed an increasing tendency of the saturation magnetization and saturation induction with grain size, which is attributed to crystallinity increase and to reduction of demagnetizing fields in the grains. The variation in coercivity could be related to anisotropy field changes within the samples due to grain size changes. In particular, the starting appearance of room temperature ferromagnetic order suggested by the sigmoid-shaped B-H loops seems to be dependent on a sufficient number of large enough magnetic domain-containing grains having been formed in the microstructure. Viewed simultaneously, the hysteresis loops appear to belong to three groups with different magnetism-type dominance, respectively dependent on phase purity and three different groups of grain size distributions.

  12. Saturation and hysteresis effects in ionospheric modification experiments observed by the CUTLASS and EISCAT radars

    Directory of Open Access Journals (Sweden)

    D. M. Wright

    2006-03-01

    Full Text Available The results of high latitude ionospheric modification experiments utilising the EISCAT heating facility at Tromsø are presented. As a result of the interaction between the high power pump waves and upper hybrid waves in the ionosphere, field-aligned electron density irregularities are artificially excited. Observations of these structures with the CUTLASS coherent HF radars and the EISCAT incoherent UHF radar exhibit hysteresis effects as the heater output power is varied. These are explained in terms of the two-stage mechanism which leads to the growth of the irregularities. Experiments which involve preconditioning of the ionosphere also indicate that hysteresis could be exploited to maximise the intensity of the field-aligned irregularities, especially where the available heater power is limited.

    In addition, the saturation of the irregularity amplitude is considered. Although, the rate of irregularity growth becomes less rapid at high heater powers it does not seem to fully saturate, indicating that the amplification would continue beyond the capabilities of the Tromsø heater - currently the most powerful of its kind. It is shown that the CUTLASS radars are sensitive to irregularities produced by very low heater powers (effective radiated powers <4 MW. This fact is discussed from the perspective of a new heating facility, SPEAR, located on Spitzbergen and capable of transmitting high frequency radio waves with an effective radiated power ~10% of that of the Tromsø heater (28MW.

  13. Magnetization, shape memory and hysteresis behavior of single and polycrystalline FeNiCoTi

    International Nuclear Information System (INIS)

    Sehitoglu, H.; Efstathiou, C.; Maier, H.J.; Chumlyakov, Y.

    2005-01-01

    We report on the shape memory characteristics and magnetic behavior of polycrystalline and single crystalline FeNiCoTi. Predeforming the samples in the martensitic state and biasing of the martensite variants produced anisotropy in the magnetization behavior allowing the 'easy axis' to be identified as the 'a-axis' in the martensitic state. Based on these results, we provide an estimate of the magnetic anisotropy energy as 8.34x10 5 ergs/cm 3 . The results confirm the different magnetization behavior in the martensitic and austenitic states, and the shift in transformation temperatures upon application of a magnetic field. Shape memory strains near 2.5% are demonstrated under constant stress temperature cycling and upon heating at zero stress after deformation. We present a thermodynamics based theory that explains the origin of the hysteresis in this class of alloys emanating from the dissipation of energy due to plastic deformation. We predict the thermal hysteresis (135 K), and the shift in transformation temperature (14 K) with applied magnetic fields in agreement with the experimental results. The possibility of utilizing these classes of alloys as magnetic shape memory alloys is discussed

  14. Temporal dynamics of plant succession in abandoned field in Mediterranean mountain areas: farming terraces and sloping fields (Iberian System, Spain)

    Science.gov (United States)

    Nadal-Romero, Estela; Errea, Paz; Lasanta, Teodoro

    2017-04-01

    Cropland abandonment is an important problem in mountain areas worldwide. This process represents the change from an agricultural management to an abandoned land in which a complex plant succession process occurs, with important hydromorphological effects, and consequences in water resources availability and soil erosion. Literature indicates that plant succession depends on multiple natural factors (soil properties, topography, climate, lithology, and distance to natural covers…) and anthropogenic factors (age of abandonment, management of each field during the cultivation period and after the abandonment…). Despite the advances, much is unknown about the vegetation succession, due to the complexity of ecological and social conditions in which land abandonment occurs. Recently, it is shown that only local factors can explain the heterogeneity of the process (Burel and Baudry, 2002; Jouba and Alados, 2012). In this work, we analyze the diversity of vegetation cover in abandonment fields in Cameros Viejo (Iberian System, Spain), related to the different field patterns (terraces and sloping fields) and the age of abandonment. Agricultural lands were delimited using aerial photographs from 1956 and 1978. The current land cover was obtained from SIOSE (Information System of Land Occupation in Spain). According to our cartography, cultivated land occupied as much as 15,491 ha (39% of the area), remaining abandoned 14,505 ha by 1978. Farming terraces occupied 55.9% of the abandoned area, and 44.1% as sloping fields. On the other hand, our cartography highlights the complexity of current land cover of abandoned fields in a landscape matrix of scrubland. Our results suggest that ecological succession is faster in farming terraces than in sloping fields, mostly until scrubland phase is attained. They also suggest that current land cover is better explained by the physical conditions of each field than by the abandonment age. Acknowledgement This research was supported

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

    Directory of Open Access Journals (Sweden)

    Yi Li

    2015-07-01

    Full Text Available 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.

  16. A hysteresis phenomenon in NMR spectra of molecular nanomagnets Fe8: a resonant quantum tunneling system

    Science.gov (United States)

    Yamasaki, Tomoaki; Ueda, Miki; Maegawa, Satoru

    2003-05-01

    A molecular nanomagnet Fe8 with a total spin S=10 in the ground state attracts much attention as a substance which exhibits the quantum tunneling of magnetization below 300 mK. We performed 1H NMR measurements for a single crystal of Fe8 in temperature range between 20 and 800 mK. The spectra below 300 mK strongly depend on the sequence of the applied field and those in the positive and negative fields are not symmetric about zero field, while they are symmetric above 300 mK. We discuss the origin of this hysteresis phenomenon, relating to the initial spin state of molecules, the resonant quantum tunneling and the nuclear spin relaxation process.

  17. A hysteresis phenomenon in NMR spectra of molecular nanomagnets Fe8: a resonant quantum tunneling system

    International Nuclear Information System (INIS)

    Yamasaki, Tomoaki; Ueda, Miki; Maegawa, Satoru

    2003-01-01

    A molecular nanomagnet Fe8 with a total spin S=10 in the ground state attracts much attention as a substance which exhibits the quantum tunneling of magnetization below 300 mK. We performed 1 H NMR measurements for a single crystal of Fe8 in temperature range between 20 and 800 mK. The spectra below 300 mK strongly depend on the sequence of the applied field and those in the positive and negative fields are not symmetric about zero field, while they are symmetric above 300 mK. We discuss the origin of this hysteresis phenomenon, relating to the initial spin state of molecules, the resonant quantum tunneling and the nuclear spin relaxation process

  18. Domain wall dynamics in ultrathin Pt/Co/AlOx microstrips under large combined magnetic fields

    Science.gov (United States)

    Jué, E.; Thiaville, A.; Pizzini, S.; Miltat, J.; Sampaio, J.; Buda-Prejbeanu, L. D.; Rohart, S.; Vogel, J.; Bonfim, M.; Boulle, O.; Auffret, S.; Miron, I. M.; Gaudin, G.

    2016-01-01

    The dynamics of magnetic domain walls in ultrathin strip-patterned Pt/Co/AlOx samples with perpendicular easy axis has been studied experimentally under an easy-axis field, superposed to a hard-axis field oriented along the strip. The easy-axis field is large so that the domain walls move well beyond the creep regime. A chiral effect is observed where the domain wall velocity shows a monotonous and surprisingly large variation with an in-plane field. A micromagnetic analysis, combining analytic, one-dimensional, and two-dimensional simulations with structural disorder, shows that this behavior can be reproduced with a Dzyaloshinskii-Moriya interaction of the interfacial type, with due consideration of the dynamics of the tilt degree of freedom of the domain wall. The estimated effective value of this interaction (D ≈-2.2 mJ /m2 for a 0.6 nm Co thickness) is consistent with values obtained by other techniques. It is also shown, by micromagnetic analysis, that several modes and characteristic times occur in the dynamics of the tilt of such domain walls.

  19. Dynamical analysis of the magnetic field line evolution in tokamaks with ergodic limiters

    Energy Technology Data Exchange (ETDEWEB)

    Ullmann, Kai; Caldas, Ibere L. [Sao Paulo Univ., SP (Brazil). Inst. de Fisica

    1997-12-31

    Full text. Magnetic ergodic limiters are commonly used to control chaos in the tokamak border and several models have been developed to study the influence of these limiters on the magnetic field line evolution in the tokamak vessel. In this work we derive a bidimensional symplectic mapping describing this evolution with toroidal corrections. Poincare plots presenting typical Hamiltonian behaviour, such as island chains and hetero clinic and homo clinic orbits are obtained. Then we perform the dynamical analysis of these Poincare plots using standard algorithms such as calculation of Lyapunov exponents, safety factors, FFT spectra and parameters space plots to perform the dynamical analysis. (author)

  20. The dynamics of the nuclear disassembly in a field-theoretical model at finite entropies

    International Nuclear Information System (INIS)

    Knoll, J.; Strack, B.

    1984-10-01

    The expansion phase of a hot nuclear system as created in an energetic heavy-ion collision is calculated and discussed by a selfconsistent field-theoretical model. Dynamical instabilities arising during the expansion from strong fluctuations of the one-body density are included explicitely. First multiplicity distributions and mass spectra resulting from a series of numerical runs in a 2+1 dimensional model world are presented. The dependence of break-up dynamics both on the properties of the binding force and possible correlations in the initially compressed hot state are discussed. (orig.)