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  • 1
    Electronic Resource
    Electronic Resource
    Equilibrium Unemployment Rate and Customs Union (1998)
    Oxford, UK and Boston, USA : Blackwell Publishers Ltd
    Pacific economic review 3 (1998), S. 0 
    Details
    ISSN: 1468-0106
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Notes: This paper utilizes the macroeconomics concept of the equilibrium rate of unemployment for theorems on free trade and the formation of customs union. The notion of an equilibrium rate of unemployment appears in the literature on labour, macroeconomics, business cycles and trade theory. Such an equilibrium rate can be derived in a number of ways, for example, by introducing labor–leisure choice in the utility functions of the workers; a labor turnover model and/or by introducing shirking. We extend the two sector-two factor Heckscher–Ohlin–Samuelson model for a small open economy by relaxing the assumption of inelastic labor supply. Specifically, we consider the classical labor supply function obtained from the representative consumer's utility maximisation problem. This consideration allows for the existence of unemployment and we analyse the effects trade policies have on the equilibrium unemployment rate. Given the movement towards free trade (either via the implementation of GATT and/or formation of customs union) it is important to examine its implications for the equilibrium rate of unemployment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/1468-0106.00051
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  • 2
    Electronic Resource
    Electronic Resource
    Loss measurements on amorphous alloys under sinusoidal and distorted induction waveform using a digital feedback technique : 37th Annual conference on magnetism and magnetic materials (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5375-5377 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A newly developed digital feedback wattmeter, allowing power loss measurements in soft laminations under generic induction waveform is presented. The system is intrinsically free of auto-oscillations, typical drawback of analog feedback circuits, and can therefore be operated in a wide frequency range (0.5 Hz–100 kHz). Loss measurements performed by this setup under sinusoidal and distorted induction waveforms on Co based amorphous ribbons are reported. It is shown that the classical approximation to the prediction of power losses under distorted induction largely fails to account for the experimental results. A novel theoretical approach, based on the statistical theory of losses, is discussed and successfully applied to the experiments. In particular, it is shown that knowledge of the loss components under sinusoidal induction at a given magnetizing frequency permits one to make an accurate prediction of the effect of distortion at that frequency as well as other ones. Illustrative applications at 1 kHz and 100 kHz are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353735
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  • 3
    Electronic Resource
    Electronic Resource
    Power losses in magnetic laminations with hysteresis: Finite element modeling and experimental validation : The 41st annual conference on magnetism and magnetic materials (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 5606-5608 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Dynamic hysteresis loop shapes and magnetic power losses are studied in nonoriented Fe-Si laminations exhibiting significant excess losses. Measurements are carried out under controlled sinusoidal induction in the frequency range from 1 Hz to 1.6 kHz, at various peak inductions from 0.25 to 1.5 T. Excess losses are found to obey a f3/2 law up to frequencies of 200–400 Hz, depending on peak induction. Beyond this limit, definite deviations are observed, due to eddy current shielding. Detailed information on the flux and field distribution in this high frequency regime is obtained by finite element solutions of Maxwell equations employing the dynamic Preisach model to describe quasi-static hysteresis and dynamic wall processes. The agreement between theoretical predictions and measurements is discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364614
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  • 4
    Electronic Resource
    Electronic Resource
    Hysteresis phenomena and Barkhausen-like instabilities in the Sherrington–Kirkpatrick spin-glass model (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5255-5257 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigate by computer simulations the hysteresis and instability phenomena taking place in the Sherrington–Kirkpatrick (SK) spin-glass model at zero temperature in the presence of field H varying in time at a given rate ||H(overdot)||. At low ||H(overdot)||, the system evolves by well-separated Barkhausen-like spin-flip clusters, which generate through a branching mechanism a sequence of metastable spin configurations associated with different values of H. On this basis, a new method to search for the lowest-energy states by applying a proper field history is proposed. The spin behavior versus ||H(overdot)|| is studied by evaluating the power spectrum of the magnetization rate associated with spin flipping. Close similarities with the properties of the Barkhausen effect in ferromagnetic materials are found. This result suggests that the SK model can to some extent describe the intricate, long-range magnetostatic interactions governing Barkhausen effect phenomenology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344628
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  • 5
    Electronic Resource
    Electronic Resource
    Study of hysteresis phenomena in Ising-like pseudospin systems with random local reversal fields and random spin-spin interactions : 35th annual conference on magnetism and magentic materials San Diego California (USA) 29 Oct − Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5066-5068 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the hysteresis properties of a generalization of the Sherrington–Kirkpatrick spin-glass model, including, in addition to the random spin-spin coupling costants {Jij}, a random distribution {hci} of local spin coercive fields, hindering spin flipping. The system evolution is driven by the time-dependent external field H(t). We investigate numerically the behavior as a function of H of the average magnetization per spin, m(H), and of the spin internal field distribution P(h;H). A rich variety of m(H) hysteresis loops is obtained, whose properties are controlled by the parameters of the {Jij} and {hci} distribution. It is found that the contributions of {Jij} and {hci} to the coercive field of these loops simply add to each other. An approximate Fokker–Planck equation for P(h;H) is derived, which permits one to understand the main features of P(h;H). In particular, it leads to a natural interpretation of the fact, put in evidence by computer simulations, that P(h;H) is, for small h, a linear function of h, whose slope is independent of H and of the {hci} distribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348149
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  • 6
    Electronic Resource
    Electronic Resource
    Reversible and irreversible magnetization in soft iron-based polycrystalline materials : 35th annual conference on magnetism and magnetic materials (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5930-5932 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The magnetization process has been investigated in nonoriented SiFe alloys over a wide induction range, from about 10−4 T to technical saturation. Special attention has been devoted to the role of grain size 〈s〉. The low-field behavior of the initial magnetization curve is characterized by a number of remarkable features: (1) the permeability μr tends, in the limit of vanishing applied field H, to a constant value, independent of 〈s〉; (2) the increase of μr with H exhibits a nonlinear behavior, in contrast with the Rayleigh law; and (3) the larger the grain size, the steeper the rise of μr with H. This effect is attributed to an increased ease of propagation of locally induced magnetization reversals at larger 〈s〉 values. Experiments put in evidence a correlation between μr and the length of propagation λ, which is found to vary as μ1/2r. However, at high inductions (above about 1 T), larger grains imply a reduction of permeability, due to the growth of unfavorable crystallographic textures. Grain size also affects power losses to a large extent. Measurements performed at 1 and 1.5 T show that the hysteresis component Ph and the excess eddy component Pe, respectively, vary as 1/(square root of)〈s〉 and (square root of)〈s〉 in the investigated range 45 μm≤〈s〉≤360 μm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347819
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  • 7
    Electronic Resource
    Electronic Resource
    Application of the Preisach and Jiles–Atherton models to the simulation of hysteresis in soft magnetic alloys (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4373-4375 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: This article describes the advances in unification of model descriptions of hysteresis in magnetic materials and demonstrates the equivalence of two widely accepted models, the Preisach (PM) and Jiles–Atherton (JA) models. Recently it was shown that starting from general energy relations, the JA equation for a loop branch can be derived from PM. The unified approach is here applied to the interpretation of magnetization measured in nonoriented Si–Fe steels with variable grain size 〈s〉, and also in as-cast and annealed Fe amorphous alloys. In the case of NO Fe–Si, the modeling parameter k defined by the volume density of pinning centers is such that k(approximate)A+B/〈s〉, where the parameters A and B are related to magnetocrystalline anisotropy and grain texture. The value of k in the amorphous alloys can be used to estimate the microstructural correlation length playing the role of effective grain size in these materials. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369788
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of stress anisotropy on hysteresis and Barkhausen noise in amorphous materials (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4412-4414 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Hysteresis, power losses, and the Barkhausen effect are investigated in an Fe-based highly magnetostrictive amorphous material, as a function of applied stress. By means of the static and dynamic Preisach model, and of existing theories of the Barkhausen effect, the results are shown to be compatible with the existence of a characteristic structural length δc, playing a role similar to that of grain size in crystalline materials. At low applied stresses, where the magnetization process is dominated by quenched-in stresses σi, δc is identified with the typical wavelength of σi fluctuations. The theoretical analysis leads to the estimate δc∼70–100 μm and 〈σi〉∼3.5 MPa. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.369801
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  • 9
    Electronic Resource
    Electronic Resource
    High frequency magnetic properties of polymer-bonded Terfenol-D composites (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 85 (1999), S. 4633-4635 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We measure the high frequency magnetic properties of polymer-bonded Terfenol-D rods compacted from powders of different size, in order to analyze the effect of structure and preparation conditions in sonic or ultrasonic frequency applications. Magnetic characterization at high fields and in the kilohertz range is made using a custom built amorphous metal yoke. Experimental data are analyzed using the theory of losses and the dynamic Preisach model. The electrical resistivity is estimated to be about 1.25 μΩ m, higher than in grain-oriented materials. The classical contribution to dynamic power loss, directly proportional to conductivity, is found to be dominant. The analysis establishes a direct connection between static and dynamic magnetic properties and structural characteristics, such as the density, conductivity, and the powder size, which can be modified for optimization purposes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370431
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  • 10
    Electronic Resource
    Electronic Resource
    Domain-wall motion in random potential and hysteresis modeling : The 7th joint MMM-intermag conference on magnetism and magnetic materials (1998)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 83 (1998), S. 6497-6499 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Two different approaches to hysteresis modeling are compared using a common ground based on energy relations, defined in terms of dissipated and stored energy. Using the Preisach model and assuming that magnetization is mainly due to domain-wall motion, one can derive the expression of magnetization along a major loop typical of the Jiles–Atherton model and then extend its validity to cases where mean-field effects and reversible contributions are present. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.367740
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