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  • 1
    Electronic Resource
    Electronic Resource
    Thermal diffusivity/conductivity in SiAlON ceramics (1995)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 77 (1995), S. 494-496 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Thermal diffusivity and conductivity of ceramic materials in a system of Si3N4-SiO2-Al2O3-AlN composed of α and β SiAlON (which is well known as duophase SiAlON ceramics) are investigated. Single-phase β-SiAlON ceramic has a thermal conductivity of 12.44 W/m K. The thermal conductivities of SiAlON ceramics decrease linearly with increasing content of α phase and can be best described by the following equation: K=12.46–0.043 f, where f is the weight percentage of α-SiAlON content and K is the thermal conductivity of SiAlON ceramics. The thermal conductivity of single-phase α-SiAlON was then estimated to be ∼8.16 W/m K, which is in excellent agreement with the literature reported values, ∼8.4 W/m K. This estimation is also close to the value, 8.22 W/m K, obtained by using Bruggeman's variable dispersion theory. The temperature dependence of the thermal conductivity of duophase SiAlON ceramics varies with α and β phase contents in the materials. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.359030
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  • 2
    Electronic Resource
    Electronic Resource
    A graphical method for estimating overshoot in convective stellar atmospheres (1974)
    Springer
    Astrophysics and space science 27 (1974), S. 303-305 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A graphical method for estimating convective overshoot in stellar atmospheres is proposed. Applying the method to the solar atmosphere, we find that a convective element which starts at a depth of about 1000 km below the top of convection zone can penetrate to a height about 300 km above it.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00643879
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  • 3
    Electronic Resource
    Electronic Resource
    Response of an optically thin, isothermal atmosphere to a convective overshoot (1974)
    Springer
    Solar physics 37 (1974), S. 53-62 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Radiation is believed to be hostile to the generation of gravity waves by granulation at the base of photosphere where the radiation is effective. A convective overshoot from subphotosphere seems able to penetrate to a height where the solar temperature is minimum and to excite the gravity waves in a stable region there. The response of the solar atmosphere to a Gaussian disturbance characterizing such a convective overshoot is studied in an unbounded isothermal atmosphere. Radiative effects are included, but only in regions which are optically thin. The response is measured in terms of mean vertical kinetic energy density (E z) and mean vertical external energy flux (Q z). E z and Q z were calculated for a wide range of frequencies centered at the observed 5-min velocity oscillation period. The computed sharp and broad power spectra at the lower chromosphere and the upper photosphere, respectively, are attributed to the combined effects of space damping and source function. Low-frequency waves (2000 s or longer) are found to be not responsible for depositing energy in the upper solar atmosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00157843
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  • 4
    Electronic Resource
    Electronic Resource
    Velocity oscillations in solar plage regions (1972)
    Springer
    Solar physics 25 (1972), S. 380-401 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The properties of wave propagation in a perfectly electrically conducting, plane-stratified, inviscid, compressible atmosphere premeated by a horizontal magnetic field which varies with height are investigated. It is shown that a diagnostic diagram can be constructed through a generalization of the propagation equation to account for the presence of a magnetic field. The effect of the magnetic field on the oscillations in solar plages around the temperature minimum is studied and compared with the non-magnetic case based on the Bilderberg Continuum Atmosphere. Due to the joint action of ionization and the magnetic field, a potential well for internal gravity waves is formed. The properties of the trapped waves are in qualitative agreement with the observations. The Brunt-Väisälä frequencies in the presence (N) and absence (N 0) of the magnetic field around the temperature minimum are shown to obey the relation N/N 0 ≈ (1 + β 2)−1/2, where β is the ratio between the Alfvén and the sonic speeds. The modified Brunt-Väisälä frequency (N) is decreased as the strength of the magnetic field increases. The magnetic effect makes the potential well shallower, thus shrinking the domain for the trapped gravity modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00192336
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