Journal Articles

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Journal Articles (Electrical and Electronics Engineering)

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    Electrical properties of CuPbBr3
    ( Solid State Ionics, 1989-05) kuku, T.A; Chioba, E.R; Chiodelli, G.
    Electrolyte characterisation of CuPbBr3 has shown the material to be appreciably conductive with a room temperature conductivity of 2.3×10−4(Ω cm)−1, and a value of 1.37×10−2 (Ω cm)−1 at 210°C. Conductivity is mainly by anionic type defects, with ionic transport numbers greater than 0.98 for all temperatures considered in the range from 22 to 215°C. The activation energy for bromine vacancy motion is 0.27 eV. X-ray, DTA and TG analyses also show that the material is characterised by a cubic lattice with lattice parameter a0 = 9.08 Å, melts at 271°C and is thermally stable up to 450°C.
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    Theoretical study of the effect of different types of tropical rainfall on microwave and millimeter-wave propagation
    (1999-09) Ajewole, Oludare; Kolawole, L.B; Ajayi, G.O
    In this paper, the effects of tropical rainfall on the propagation of microwave and millimeter-wave signals on terrestrial paths have been investigated. Quantitative evaluation of spheroidal raindrop scattering parameters such as the scattering amplitude functions, total and scattering cross sections, and so on, were carried out for linear polarization (horizontal and vertical), using the least squares fitting method over the frequency range 1–100 GHz. Incident radio signals are assumed plane and arrive normally on the raindrop axis. For the purpose of application to slant paths, two other incident angles, 50° and 70°, were considered. The computed forward scattering amplitude functions were employed to compute the complex effective propagation constant of the radio signals in four tropical rainfall types: drizzle, widespread, shower, and thunderstorm. The corresponding specific attenuation and specific phase shift were computed. Specific attenuation and phase shift due to the rain types for circularly polarized radio signals were also derived. The parameters of the power law relationship between attenuation, phase shift, and rain rate were computed for each rain type and compared with existing temperate and tropical models. The problem of rain-induced depolarization was also investigated by computing the cross polarization discrimination for the four rainfall types over the frequency range 1-50 GHz, which is of immediate importance to system designers
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    Installing a 3 node Linux based cluster for scientific computation
    (2006-08) Sokunbi, O.Moses
    This paper describes the installation of a 3 node Linux based cluster for scientific computation. The cluster entails a node as the master node and the other two nodes as the compute nodes. The compute nodes are installed by a network based kickstart installation system. Scientific packages such as compilers, mathematical libraries, Local Area Multicomputer (LAM) package for Message Passing Interface (MPI), batch processing and scheduling software are installed. The output of the Ganglia monitoring package is shown. An mpi job is compiled and ran in order to test the application packages.
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    Electrical Properties of Silver Impurities and their Annealing Behaviour in p-Type Fz Silicon
    (Journal de Physique III, 1691-12) Adegboyega, G.A; Passari, L; Butturri, Maria Angela; Poggi, Antonella
    The electrical activity of silver as well as its annealing properties in 10 Omega cm p-type Fz silicon substrate are studied by means of the four-point probe and minority carrier lifetime measurements. Silver atom concentration in the range 10^{14} to 10^{15} cm^{-3} consistently showed a donor type behaviour in the material and its presence led to a reduction of up to two orders of magnitude in the lifetime of minority carriers by the formation of deep-level traps. Isochronal annealing of silver contaminated specimens showed some gettering of the Ag impurities with resulting temperature dependent changes in the resistivity as well as the minority carrier lifetime values. Analysis of our results shows that a large fraction of the silver impurity atoms present forms the deep level defects and both the deep- and donor-levels appear to originate from the same source
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    Preparation and characterization of MOCVD thin films of indium tin oxide
    (Optical Materials, 1999-11) Akinwunmi, O.O; Eleruja, Marcus Adebola; Olowolafe, J.O; Adegboyega, G.A
    Indium Tin Oxide (ITO) was deposited by pyrolysis of mixed metal acetylacetonate (a single solid-source precursor). This study demonstrates that the properties of the as-deposited film depend on the deposition temperature. Films with a resistivity of , a visible transmission of over 80%, and a direct optical energy gap of 3.76 eV were deposited.