NOPR Collection:

FDTD based SAR analysis in human head using irregular volume averaging techniques of different resolutions at GSM 900 band

2016-07-20T06:06:11Z

Title: FDTD based SAR analysis in human head using irregular volume averaging techniques of different resolutions at GSM 900 band Authors: Ali, Md Faruk; Ray, Sudhabindu Abstract: Specific absorption rate (SAR) induced inside human head in the near-field of a mobile phone antenna has been investigated for three different SAR resolutions using Finite Difference in Time Domain (FDTD) method at GSM 900 band. Voxel based anthropomorphic human head model, consisting of different anatomical tissues, is used to calculate the peak SAR values averaged over 10-g, 1-g and 0.1-g mass. It is observed that the maximum local SAR increases significantly for smaller mass averages. Page(s): 235-242

0°C isotherm height distribution for Earth-space communication satellite links in Nigeria

2016-07-20T06:05:09Z

Title: 0°C isotherm height distribution for Earth-space communication satellite links in Nigeria Authors: Ojo, J S; Falodun, S E; Odiba, O Abstract: For an optimum performance of Earth-space satellite communication links, a number of meteorological parameters are needed to be considered along the Earth-space path for specific locations and the height of the 0°C isotherm (freezing level height) is among such parameters. Information regarding this parameter is always based on the recommendation of ITU-RP-839 in the form of contour maps. Since the meteorological parameters are location dependent, there is a need for the establishment of these parameters for specific locations. In addition, ITU-R model uses an yearly averaged constant rain height for the attenuation estimation, which may not be appropriate for tropical regions. In the present paper, the 0°C isotherm (ZDI) height has been established using two years of data collected on-board the precipitation radar of the Tropical Rain Measuring Mission (TRMM) satellite. The result shows the seasonal dependence of the 0°C isotherm height. It is observed, among other things, that the height is higher during the wet season as compared to the dry season. Rain induced attenuation at frequencies above 10 GHz is also estimated using the 0°C isotherm height derived for each of the locations over the elevation angle of the NIGCOMSAT-1R in Nigeria. Page(s): 225-234

Estimation of global solar radiation in Nigeria using a modified Angstrom model and the trend analysis of the allied meteorological components

2016-07-20T06:03:57Z

Title: Estimation of global solar radiation in Nigeria using a modified Angstrom model and the trend analysis of the allied meteorological components Authors: Ogolo, E O Abstract: The trend of some common and related atmospheric variables were investigated in the light of climate change on annual time scale and a suitable scheme was further developed for the simulation of annual global solar radiation in Nigeria. In this connection, annual trends of global solar radiation, air temperature, precipitation, relative humidity and sunshine hours was carried out, covering about 13 tropical stations during 1975-2006 in Nigeria using F-test as the significance test technique. It was found that nine stations exhibited an upward trend in global solar radiation series, of which 6 passed F-test at 1% significant level. At 11 stations, precipitation had shown an increasing trends but none passed F-test at 2.5% and hence, not significant. About 98.8% of the stations displayed an upward trend in sunshine hours of which 16% passed F-test at 1% significant level. On trend analysis for relative humidity series, eight stations exhibited a positive trend and only one station passed F-test at 1% significant level. The trend of temperature series in Nigeria under the period under investigation was found to be increasing at 12 stations and eight stations passed the F-test at 1% significant level. The other objective of this study was to determine a more suitable empirical equation by modifying Angstrom model for the estimation of global solar radiation using all data for all 14 stations pooled together to predict global solar radiation using linear and multiple linear regression. This was done to improve the low performance of the Angstrom model used for the annual estimation of global solar radiation. The model parameters ‘a’ and ‘b’ of Angstrom model were parameterized in terms of the geographical locations (latitude, longitude and elevation) and the meteorological variables (sunshine hour, precipitation, relative humidity and temperature), respectively. This scheme gave better simulation of the global solar radiation compared with other schemes and the original Angstrom models. In addition, the preferential consideration of relative humidity to precipitation as potent contributing factor in the estimation of global solar radiation was also established. Page(s): 213-224

Modelling of the equatorial ionospheric E-layer based on cos index

2016-07-20T06:02:35Z

Title: Modelling of the equatorial ionospheric E-layer based on cos index Authors: Kazeem, A K; Adeniyi, J O; Adediji, A T Abstract: Daytime hourly values of the critical frequency of the ionospheric E-layer, oE, obtained at Ouagadougou Ionospheric Observatory (12.4°N, 1.5°W) in Burkina Faso, West Africa, an equatorial station, during the solar cycle 22 (1985 – 1995) have been used to develop a model based on solar zenith angle through cosc index factor using the relation oE = a (cos)ⁿ_, The average value of the diurnal cos index, n, at Ouagadougou was found to be 0.30 for both low and high solar activity. The model was tested with oE data from Korhogo (9.3°N, 5.4°W) in Cote-d’Ivoire, another equatorial station, and there is good agreement between the model and observations. The validity of the oE model was also compared with predicted values by IRI-2012 model and good agreement has been observed. The percentage difference, when oE observed compared with IRI-2012 model, was found to be within ±10% for both equinoxes and solstices for the two levels of solar activity. Page(s): 205-212