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  • 1990-1994  (3)
  • 1992  (3)
  • 1
    Electronic Resource
    Electronic Resource
    High-n helicity-induced shear Alfvén eigenmodes (1992)
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 4 (1992), S. 1115-1121 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The high-n helicity-induced shear Alfvén eigenmodes (HAE) are considered both analytically and numerically for the straight helical magnetic system, where n is the toroidal mode number. The eigenmode equation for the high-n HAE modes is derived along the field line and, with the aid of the averaging method, is shown to reduce to the Mathieu equation asymptotically. The discrete HAE modes are shown to exist inside the continuum spectrum gaps. The continuous spectrum gaps appear around ω2=ω2A[N(lι(large-closed-square)−m)/2]2 for N=1,2,..., where ωA is the toroidal Alfvén transit frequency, and l, m, and ι(large-closed-square) are the polarity of helical coils, the toroidal pitch number of helical coils, and the rotational transform, respectively. For the same ωA and ι(large-closed-square), the frequency of the helical continuum gap is larger than that of the continuum gap in tokamak plasmas by ||l−ι(large-closed-square)−1m||. The polarity of helical coils l plays a crucial role in determining the spectrum gaps and the properties of the high-n HAE modes. The spectrum gaps near the magnetic axis are created by the helical ripple with circular flux surfaces for l=1, and ≥3 helicals. For l=2 helical systems, the spectrum gaps are created by the ellipticity of the flux surfaces. These analytical results for the continuum gaps and the existence of the high-n HAE modes in the continuum gaps are confirmed numerically for the l=2 case, and it is found that the HAE modes exist for mode structures with the even and the odd parities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.860119
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Gate-voltage dependence of the critical current of the superconducting field effect transistor (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 2473-2475 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The saturation of the critical current as a function of the gate voltage found in the Nb-Si-Nb superconducting field effect transistor is analyzed numerically using the de Gennes expression for the proximity effect. According to the analysis, (i) the Schottky barrier effect is found to be negligible under experimental conditions, (ii) mobility of silicon fitted to the experimental curve shows a power relation to the gate voltage with exponent of about −0.81. This exponent is consistent with the results from independent experiments and a simple theory of surface scattering. The results indicate that the surface scattering effect causes the saturation phenomenon.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.108156
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Preparation of octadecyl modified column gels using heat-treated silicas and their retention behaviour in high-performance liquid chromatography (1992)
    Springer
    Chromatographia 33 (1992), S. 203-207 
    Details
    ISSN: 1612-1112
    Keywords: Column liquid chromatography ; Octadecyl modified silica ; Hexamethyldisilazane treated silica ; Calcination ; Heat-treated silica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The effect of silanol groups on three types of octadecylmodified column gels using heat-treated silicas by calcination has been studied by high-performance liquid chromatography. After heat-treating at 180°C, 500°C and 950°C, the silicas treated with octadecyldimethylchlorosilane were used for the measurement of physical and chemical analysis. From elemental carbon analysis data, the reactive silanol group concentrations, αOH(s), were determined to be 2.0 in the 180°C treated silica, 2.1 in the 500°C treated silica and 1.6 in the 950°C treated silica, respectively (original silica: mean pore diameter 116 Å, specific surface area 298 m2/g, pore volume 1.22 ml/g, particle size 5.0 μm). The separation factors, α, of pyridine versus phenol were measured to be 0.79 on 180°C treated silica, 0.91 on 500°C treated silica and 1.98 on 950°C treated silica, using acetonitrile-water mixtures as the eluent. And then, on the basis of the physico-chemical and chromatographic data, the three types of octadecyl modified column gels using heat-treated silicas by calcination have been compared.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02276183
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    Paper (German National Licenses)
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