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  • 1
    Electronic Resource
    Electronic Resource
    OPTIMUN SIMULTANEOUS PREDICATION INTERVALS IN ECONOMETRIC FORECASTING (1972)
    Oxford, UK : Blackwell Publishing Ltd
    Metroeconomica 24 (1972), S. 0 
    Details
    ISSN: 1467-999X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Economics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1467-999X.1972.tb00192.x
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  • 2
    Electronic Resource
    Electronic Resource
    A study of the oxidation kinetics of CuFeO2 in the Cu-Fe-O system (1981)
    Springer
    Journal of materials science 16 (1981), S. 102-110 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation kinetics of CuFeO2 in the Cu-Fe-O system have been studied between 500 and 900° C in an atmosphere containing 1 vol% oxygen in a nitrogen stream using thermogravimetric analysis (TGA). It was found that addition of Fe2O3 to the CuFeO2 caused a decrease in the oxidation rate while addition of CuO caused an increase. On increasing the concentration of Fe2O3 the activation energy was found to increase from ~ 18 kcal mol−1 to ~ 45 kcal mol−1 and the exponent ‘n’ in Avrami's equationf=1-exp (−kt n) was also observed to increase, from 1.3 to 2.3. On adding CuO to the CuFeO2 in the Cu-Fe-O system the activation energy decreased from ~ 18 kcal mol−1 to ~ 8 kcal mol−1. The variation in both values indicates changes in the oxidation mechanisms. The microstructural changes associated with oxidation have been studied using optical microscopy. A model has been proposed to explain the results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00552064
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  • 3
    Electronic Resource
    Electronic Resource
    Electrical conduction in titania-doped lanthanum chromite ceramics (1981)
    Springer
    Journal of materials science 16 (1981), S. 1994-1998 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The direct and alternating current electrical conductivities of lanthanum chromite ceramic doped with 1 to 3 wt% TiO2 have been measured at temperatures from 20 to 200° C. The sample containing 3 wt% TiO2 has been studied in detail because of all the samples it showed the highest sintered density and electrical conductivity. Alternating current conductivity, σ ac, measurements taken over the frequency range 10 kHz to 1 MHz were found to follow a power law of the form σ ac ∝ ω n , where ω is the frequency and 0.5〈n〈1, indicative of a hopping conduction mechanism. In addition, a dispersion in the dielectric constant was observed. The dispersion peak frequency has been found to be thermally activated with an activation energy of 0.423±0.002 eV. The results are successfully interpreted in terms of a model proposed by Pike, wherein a classical hopping of charge carriers (over a potential barrier) between the localized states is considered. The direct current conductivity activation energy predicted from this model is found to be consistent with the experimentally obtained value.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00540648
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  • 4
    Electronic Resource
    Electronic Resource
    Pentavalent vanadium ion addition to Ni-Zn ferrites (1983)
    Springer
    Journal of materials science 18 (1983), S. 1934-1940 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The d.c. And a.c. Electrical conductivities of iron-excess and iron-deficient compositions of Ni-Zn ferrites, with varying V2O5, content sintered at different temperatures (1200 to 1300° C) for 2 h in air, has been studied. The electrical conductivity increased with a 0.2 mol % addition of V2O5. The minimum d.c. And a.c. Electrical conductivities were found at a V2O5 content of 0.4 mol % followed by a small increase for still higher concentrations of V2O5 (⩾ 0.6 to 1.0 mol %). The minima at 0.4 mol % were unaffected by the sintering temperature in both the iron-excess and iron-deficient cases. The activation energies for a.c. Conduction at 1 MHz were always less than the corresponding values for d.c. conduction. The results obtained can be explained in terms of solubility of V2O5, which creates ferrous ions and localizes Fe2+ ions by forming triplets in the ferrite matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00554985
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  • 5
    Electronic Resource
    Electronic Resource
    On some transport properties of strontium-doped lanthanum chromite ceramics (1983)
    Springer
    Journal of materials science 18 (1983), S. 2095-2100 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract D.C. Electrical conductivity, Hall mobility and magnetic susceptibility measurements on La1−x Sr x CrO3 (0⩽x⩽0.25) perovskite ceramic system, and their temperature dependence, have been carried out to understand the nature of the transport mechanism in them. The electrical conductivity and Hall mobility displayed thermally activated temperature dependence with activation energies that varied from 0.13 to 0.23 ev. The variation of the d.c. conductivity of the polycrystalline La1−x Sr x CrO3 with strontium content (X) has been found to be strongly affected by the changes in microstructure. Magnetic susceptibility data indicate that the electronic transport is due to the presence of Cr4+ ions in the lattice, and that the localized level of hopping is associated with the chromium 3d band.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00555003
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  • 6
    Electronic Resource
    Electronic Resource
    Pentavalent vanadium ion addition to Ni-Zn ferrites (1983)
    Springer
    Journal of materials science 18 (1983), S. 1583-1589 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Systematic studies of the changes in microstructure and the grain-growth kinetics of iron-deficient and iron-excess Ni-Zn ferrites with varying contents of V2O5 have been undertaken. The basic composition of an iron-deficient Ni-Zn ferrite showed a duplex structure. Modified microstructures with pore-free and uniform grains were obtained on V2O5 doping. A regular increase in grain size was found with increasing V2O5 content both in iron-deficient and iron-excess compositions. The square of the average grain diameter varied linearly with sintering time up to 0.0 to 0.4 mol % V2O5. For higher V2O5 contents (0.6 to 1.0 mol %), the cube of the average grain diameter was directly proportional to the sintering time. Modifications in the microstructure and the grain growth have been explained in terms of the solubility of V2O5 in the lattice and liquid-phase formation at the grain boundaries.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00542050
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  • 7
    Electronic Resource
    Electronic Resource
    Infrared spectra of the ceramic LaCrO3 doped with strontium and titanium (1982)
    Springer
    Journal of materials science 1 (1982), S. 239-240 
    Details
    ISSN: 1573-4811
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00727844
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  • 8
    Electronic Resource
    Electronic Resource
    Electrical properties of phosphorus diffused GaAs (1976)
    Springer
    Journal of materials science 11 (1976), S. 741-748 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The electrical parameters, i.e. mobility, resistivity and ionization energy, of the dopant (Se) have been determined at different depths in phosphorus diffused GaAs. These values have been compared with those obtained for the epitaxially grown specimens.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01209462
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of intragranular porosity of initial permeability and coercive force in a manganese zinc ferrite (1976)
    Springer
    Journal of materials science 11 (1976), S. 1335-1338 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Initial permeability and coercive force are structure sensitive properties which depend upon intragranular porosity. It has been found that in a manganese zinc ferrite the initial permeability varies directly as the separation between intragranular pores and the coercive force varies inversely as the square root of this distance. Assuming reversible motion of the domain wall pinned at the pores, the behaviour of initial permeability with respect to the distance between the pores can be adequately explained. It is not possible to give an explanation for the observed relationship between coercive force and the distance between the pores.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00545155
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  • 10
    Electronic Resource
    Electronic Resource
    A thermogravimetric study of the oxidation of CuFeO2 (1977)
    Springer
    Journal of materials science 12 (1977), S. 1903-1908 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The oxidation kinetics of CuFeO2 have been studied between 500 and 1000° C under various oxygen partial pressures using thermogravimetric analysis (TGA). The oxidation rate was found to increase as the oxygen partial pressure was increased, and for a given partial pressure of oxygen it was found to be maximum at ∼700° C. The enthalpy and activation energy for the oxidation of CuFeO2 were calculated to be ∼26.6±2 and ∼18±2 kcal mol−1 respectively. The oxidation of CuFeO2 resulted in the formation of CuFe2O4 and CuO, and the rate of reaction followed an S-type curve as found in the pearlitic transformation in steels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00566252
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