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  • 1
    Electronic Resource
    Electronic Resource
    Very low loss ultrathin Co-based amorphous ribbon cores (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 6050-6052 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ultrathin Co-based amorphous ribbons with a thickness of 6–10 μm were fabricated by a single roller quenching method in vacuum. The compositions of the alloys were zero magnetostrictive: Fe4.7Co70.3Si15B10 and (Fe0.05Co0.95)71(Si0.5B0.5)29. The ribbons obtained had good smoothness and dimensional uniformity. The core loss of toroidal samples 15 mm in diameter was measured after annealing. The loss decreased with decreasing ribbon thickness. In the case of 6.4-μm-thick (Fe,Co)71(Si,B)29 amorphous ribbon, the values at 100 kHz and 1 MHz were 40 mW/cm3 and 1.8 W/cm3 for Bm=0.1 T, respectively. The former was 1/4 that of Mn-Zn ferrites or 1/2 that of 5-μm-thick Supermalloy tape wound core loss. The latter was (2)/(3) that of 5-μm Supermalloy tape wound core loss. In addition, the initial permeability beyond 100 kHz was also markedly improved by thickness reduction. The values of 6.4-μm-thick (Fe,Co)71(Si,B)29 ribbon measured at 1 and 10 MHz were about 7000 and 1000 for Hm=2 mOe, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.342151
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  • 2
    Electronic Resource
    Electronic Resource
    The frequency dependence of ac coercivity of ultrathin, low magnetostriction Co-based amorphous ribbons : 35th annual conference on magentism and magnetic materials San Diego, California (USA) 29 Oct − 1 Nov 1990 (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 5337-5339 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamic (ac) coercivity of zero magnetostriction Co-based ultrathin amorphous ribbons from the [(Co0.95Fe0.05)0.95Cr0.05]75Si15B10 family was measured over the frequency range of 20 Hz to 20 kHz. Ribbons with thicknesses between 5.3 and 18 μm, and widths held constant at approximately 6 mm, were studied. The results are well fit by a power law dependence of the coercivity Hc on frequency f. The exponent which characterizes the best fit to the data depends on ribbon thickness. Within experimental uncertainty, the exponent increases linearly with ribbon thickness, varying between 0.18 and 0.32 for the ribbons studied. In contrast, simple phenomenological models predict a constant value of 0.5 for the exponent. The origins of the deviations from this simple phenomenological dependence of coercivity on frequency are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.348021
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  • 3
    Electronic Resource
    Electronic Resource
    Self-sustained plasma turbulence due to current diffusion (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 4140-4148 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Plasma turbulence and anomalous transport by the electrostatic current diffusive interchange mode are studied by the nonlinear simulation based on the magnetohydrodynamic model. The turbulence is found to have a typical characteristic of subcritical turbulence. The saturation level, as a function of the pressure gradient ∇p, is confirmed to scale like ||∇p||3/2. This nature holds independent of the ratio ||∇p||/||∇pc|| where ||∇pc||, is a critical pressure gradient against linear instability. The turbulence-driven transport is also evaluated. The simulation result confirms the theoretical prediction, which is based on the self-sustained turbulence, with respect to the nonlinear growth and damping. Both the normal cascade and inverse cascade are essential in establishing the stationary turbulent state. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871038
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  • 4
    Electronic Resource
    Electronic Resource
    Reduced Braginskii equations (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 2135-2139 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A set of reduced Braginskii equations is derived without assuming flute ordering and the Boussinesq approximation. These model equations conserve the physical energy. It is crucial at finite β that the perpendicular component of Ohm's law be solved to ensure ∇⋅j=0 for energy conservation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870611
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  • 5
    Electronic Resource
    Electronic Resource
    Partition in power transfer and dissipation rate in self-sustained turbulence (1994)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 1 (1994), S. 1154-1158 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Power partition and energy dissipation rates are examined for a self-sustained stationary turbulence of a high-n ballooning mode in a tokamak plasma. It is found that the power to excite fluctuations is almost equally transferred to perpendicular ion motion and to parallel electron motion. The ratio of the thermalized power, which excites and sustains the turbulence, to the total power lost by energy diffusion is found to be of the order of the broken symmetry parameter, i.e., the inverse aspect ratio, a/R. The dissipation rates of the fluctuations due to the thermal conductivity, the electron viscosity, and the ion viscosity are also calculated separately. The dissipation is dominated by that associated with the thermal conductivity. The relation between the induced global flux and the microscopic dissipation is also derived. It is found that a fractional part of order a/R of the dissipated power is effective in sustaining the turbulent modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870711
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  • 6
    Electronic Resource
    Electronic Resource
    Numerical study of chaos based on a shell model (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Chaos 9 (1999), S. 393-402 
    Details
    ISSN: 1089-7682
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A shell model is introduced to study a turbulence driven by the thermal instability (Rayleigh–Bénard convection). This model equation describes cascade and chaos in the strong turbulence with high Rayleigh number. The chaos is numerically studied based on this model. The characteristics of the turbulence are analyzed and compared with those of the Gledzer–Ohkitani–Yamada (GOY) model. Quantities such as a mean value of total fluctuation energy, it's standard deviation, time averaged wave spectrum, probability distribution function, frequency spectrum, the maximum instantaneous Lyapunov exponent, distribution of instantaneous Lyapunov exponents, are evaluated. The dependences of these quantities on the error of numerical integration are also examined. There is not a clear correlation between the numerical accuracy and the accuracy of these quantities, since the interaction between a truncation error and an intrinsic nonlinearity of the system exists. A finding is that the maximum Lyapunov exponent is insensitive to a truncation error. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.166416
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  • 7
    Electronic Resource
    Electronic Resource
    Analysis of the current-diffusive ballooning mode (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3702-3711 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The current-diffusive ballooning mode is analyzed in the tokamak plasma. This mode is destabilized by the current diffusivity (i.e., the electron viscosity) and stabilized by the thermal conductivity and ion viscosity. By use of the ballooning transformation, the eigenmode equation is solved. An analytic solution is obtained by the strong ballooning limit. Numerical calculation is also performed to confirm the analytic theory. The growth rate of the mode and the mode structure are analyzed. The stability boundary is derived in terms of the current diffusivity, thermal conductivity, ion viscosity, and the pressure gradient for the given shear parameter. This result is applied to express the thermal conductivity in terms of the pressure gradient, magnetic configurational parameters (such as the safety factor, shear, and aspect ratio), and the Prandtl numbers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860841
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  • 8
    Electronic Resource
    Electronic Resource
    Transition from resistive-G to ηi- driven turbulence in stellarator systems (1991)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 3 (1991), S. 1638-1643 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By an electromagnetic incompressible two-fluid model describing both ion temperature gradient drift modes (ηi modes) and resistive interchange modes (g modes), a new type of ηi mode is studied in cylindrical geometry including magnetic shear and an averaged curvature of Heliotron/Torsatron. This ηi mode is destabilized by the coupling to the unstable g mode. Finite plasma pressure beta increases the growth rate of this mode and the radial mode width also increases with plasma pressure beta indicating large anomalous transport in the Heliotron/Torsatron configuration. The transport from ηi mode exceeds that from resistive g when the mean-free-path exceeds the machine circumference. For plasma beta above two to three times the Suydam limit, the m=1/n=1 growth rate increases from the ηi mode value to the magnetohydrodynamic (MHD) value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.859683
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  • 9
    Electronic Resource
    Electronic Resource
    Ion-temperature-gradient-driven modes in neoclassical regime (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 1179-1187 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A reduced set of neoclassical fluid equations, consisting of the parallel ion flow velocity v(parallel), the generalized potential F, the ion pressure p, and the parallel ion heat flow q(parallel), is derived. The resultant equations are the extension of reduced fluid equations derived from Braginskii equations with the high collisionality to the equations relevant to a fusion plasma with low to intermediate collisionality. The linear ηi mode dynamics is reinvestigated by using the resultant model equations. The effects of the perpendicular compressibility in the ion pressure response, the parallel heat flow, and the neoclassical viscosity are analyzed both analytically and numerically. It is stressed that the closure condition of neoclassical viscosity changes the sign of energy dissipation and seriously affects the stability of ηi modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860908
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  • 10
    Electronic Resource
    Electronic Resource
    Theory of pseudoclassical confinement and transition to L mode (1993)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 3299-3303 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theory of the self-sustained turbulence is developed for resistive plasma in toroidal devices. Pseudoclassical confinement is obtained in the low-temperature limit. As temperature increases, the current diffusivity prevails upon resistivity, and the turbulence nature changes so as to recover the L-mode transport. Comparison with experimental observation on this transition is made. The Hartmann number is also given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860626
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