Faculty of Applied Science and Technology

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Browsing Faculty of Applied Science and Technology by Author "Baki, Paul"

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    Astronomy in the cultural heritage of African societies
    (2006) Baki, Paul
    The African perspectives of astronomy are explored from the point of view of using indigenous knowledge of the night sky for purposes of addressing local challenges such as food insecurity and periodic natural weather phenomena such as droughts and floods. The local ethnic groups use stellar positions, and plant and animal behaviour changes for purposes of forecasting the weather and climate for the coming seasons. These traditional indicators give rise to an interdisciplinary discourse that could benefit the community in environmental protection measures and boost the tourism industry in some countries in Africa
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    Features of the Night-Time F-Region Currents Over Equatorial Africa (August, 2001)
    (2014) Adero, Awuor Ochieng; Baki, Paul; Kotze, Peter; Mito, Collins
    In this paper, we present the features of the equatorial F-region current systems over equatorial Africa during nighttime on 05thAugust, 2001 observed at midnight. The observations have inferred from in situ CHAMP satellite measurements of the vector magnetic field. The magnitudes of the current along all the three magnetic field components of the Earth’s magnetic field varied considerably. The Bx-component recorded a diamagnetic effect of about 8nT, By-component recorded a current density of 5mA/m, and Bz-component reached a value of 3mA/m. The F-region dynamo, gravity dynamo and plasmapressure gradients are the possible mechanisms for the occurrence of these currents. The signatures confined to the equatorial region bounded by the Appleton anomaly.
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    Identification of Night-Time F- Region Currents from CHAMP Satellite Observations over Equatorial Africa
    (2013) Ochieng, Adero Awuor; Baki, Paul; Kotze, Peter; Mito, Collins
    The F-region currents are generally weak and difficult to detect. However, their contributions to the earth’s magnetic field variations are significant and cannot be ignored by the field modelers. CHAMP satellite has therefore provided a perfect opportunity to investigate the in-situ F-region currents on the night side of the equatorial region. The magnitudes of the current along all the three components of the earth’s magnetic field (X, Y, Z) are investigated. However in this paper, we present only the results on the Y-component where interesting magnetic residuals were observed. The X and Z-components were rather masked in much noise and would require further filtering. The currents appear in both the pre-midnight and postmidnight sectors and are spatially confined to the equatorial region bounded by the Appleton anomaly. The magnetic residuals are generally observed in the northern hemisphere of an order of 0.8nT, which gives a height-integrated current density of about 1.3mA/m.
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    The inverse problem of acoustic wave scattering by an air-saturated poroelastic cylinder
    (2013) Ogam, Erick; Fellah, ZEA; Baki, Paul
    The efficient use of plastic foams in a diverse range of structural applications like in noise reduction, cushioning, and sleeping mattresses requires detailed characterization of their permeability and deformation (load-bearing) behavior. The elastic moduli and airflow resistance properties of foams are often measured using two separate techniques, one employing mechanical vibration methods and the other, flow rates of fluids based on fluid mechanics technology, respectively. A multi-parameter inverse acoustic scattering problem to recover airflow resistivity (AR) and mechanical properties of an air-saturated foam cylinder is solved. A wave-fluid saturated poroelastic structure interaction model based on the modified Biot theory and plane-wave decomposition using orthogonal cylindrical functions is employed to solve the inverse problem. The solutions to the inverse problem are obtained by constructing the objective functional given by the total square of the difference between predictions from the model and scattered acoustic field data acquired in an anechoic chamber. The value of the recovered AR is in good agreement with that of a slab sample cut from the cylinder and characterized using a method employing low frequency transmitted and reflected acoustic waves in a long waveguide developed by Fellah et al. [Rev. Sci. Instrum. 78(11), 114902 (2007)].
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    A Study of the Equatorial Ionosphere Over Nairobi During Selected Magnetically Disturbed and Quiet Times for the Year 2009 Using Co-Located Instruments
    (2014) Omondi, George; Ndinya, Boniface; Baki, Paul
    Investigation of the behavior of the Equatorial Ionosphere over Nairobi-Kenya within the East Africa region is done using co-located instruments, that is, SCINDA-GPS system and a Magnetometer ( MAGDAS). This was done for magnetically disturbed days, 22 and 23 July,2009, as well as for quiet days before and after the geomagnetic disturbances. TEC depletions were observed and amplitude Scintillation indices plots were made and an attempt made to correlate these with modelled surface electric fields computed from magnetic field variations. The results show that most geoelectric field enhancements occured between 0700 LT and 1300 LT mostly in the east-west component and in the post-midnight local time while scintillations and TEC enhancements and depletions occurred mostly between 0900 LT and 1100 LT during geomagnetic disturbances and between 1300 LT and 1400 LT during quiet times.This may be attributed to the development of the Equatorial Ionization Anomaly or an extension of of the neutral wind dynamo driven by the E-region neutral wind and gravity waves generated by convection. Moreover, geoelectric field enhancements were accompanied by scintillations and TEC enhancements or depletions since pre-reversal enhancement in drift controls the occurence of scintillations.
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    A study on the response of the Equatorial Ionization Anomaly over the East Africa sector during the geomagnetic storm of November 13, 2012
    (Elsevier, 2015) Olwendo, Ouko Joseph; Yosuke, Yamazak; Cilliers, Pierre; Baki, Paul; Ngwira, Chigomezyo M; Mito, Collins
    Using a set of up to 12 International GNSS Services (IGS) receivers around the East African region, we present the formation of the peak of ionospheric Equatorial Ionization Anomaly during the geomagnetic storm of 13th November 2012. The diurnal pattern of total electron content (TEC) shows a strong negative storm during the main phase of the storm. Latitudinal variation of TEC shows development of strong Equatorial Ionization Anomaly (EIA) on the recovery phase. Evidence in terms of magnetic variations during the storm period, indicates that the penetration of interplanetary electric fields is the main cause of the negative ionospheric effect during the main phase of the storm. Observation shows the occurrence of very strong westward electric fields arising from the IMF Bz turning southward a few hours after sunset local time. TEC enhancement during the recovery phase on the 16th are attributed to the increased ionospheric disturbance dynamo electric fields. In addition the EIA crest was found to intensify in amplitude as well as expand in latitudinal extent.