http://196.220.128.81:8080/xmlui/handle/123456789/238 2026-04-27T05:23:13Z 2026-04-27T05:23:13Z OJO, JOSEPH SUNDAY http://196.220.128.81:8080/xmlui/handle/123456789/5816 2026-04-10T12:40:34Z 2004-01-05T00:00:00Z

COMPARATIVE STUDY OF BISTATIC INTERSYSTEM INTERFERENCE LOCATIONS OJO, JOSEPH SUNDAY Very many prediction models have been used in recent times to estimate transmission loss arising from Bisastic scattering of terrestrial microwave signals into the receiver of Earth-space communication systems operating at the frequency. Among the models, Capsoni Simplified 3-D EXponential rain CELL (EXCELL) model has yielded the most satisfactory results for interference prediction in all rainfall climate regions. In the model, the horizontal structure of rain is the same in all region, hence only the measured cumulative distribution of point rainfall rates in the region of interest is required. This study is based on this model. It uses as input measured cumulative distribution of rainfall rates from three locations in Africa, Ile-lfe (Nigeria), Nairobi (Kenya) and Douala (Cameroon) to estimate bistatic intersystem interference (transmission loss) due to hydrometeor scattering of signals from terrestrial microwave system into the receiving terminal of a ground Earth-space communication system. Two elevation angles, 230 and 550, which are the prominent satellite look angles in Nigeria are considered. The transmission loss statistics computed for varying distances from the terrestrial System (TS) antenna to the common volume (CV) formed by the intersection of the antenna beams, varying antenna gains and varying percentage unavailabilities. Frequencies ranging from 4 to 35 GHz and two path length configurations short (≤50km) and long (> 50km) are considered; Results obtained showed that transmission loss increases with increasing TS to CV distance, implying decreasing possibility of severe interference in the sastelite system. The Variation of Transmission loss with increasing TS antenna gain shows that transmission increases with decreasing time unavailability (exceedance probability). The study also shows that for a given fade depth, the higher TS antenna gain, the higher is the probability of the ground satellite receiver picking severe interference from the terrestrial microwave network, Further, comparing the results in Kenya and Cameroon with Nigeria; it was observed that variation of transmission loss with TS to CV distance is lower by 1.3% in Kenya, while it is higher by 1.4% in Cameroon for 0.01%-time unavailability. Therefore, in Cameroon, the satellite ground receiver system is more likely receive higher interference from a microwave transmitting system Operating at the same frequency. Evaluation of the effective transmission loss in these regions also show the possibility of complete signal outage due to rain attenuation in Cameroon compared to other locations, no matter the amount interference received from the microwave system. This is because of the higher rainfall intensity find accumulated water in Cameroon. xi.: 58p.: ill.; 32cm.

2004-01-05T00:00:00Z David, H. O http://196.220.128.81:8080/xmlui/handle/123456789/5814 2026-04-10T10:57:11Z 2004-02-04T00:00:00Z

DEPOLARIZATION OF CIRCULARLY POLARIZED MILLIMETRE WAVES BY PRECIPITATION IN NIGERIA David, H. O Rain induced depolarization due to distorted rain drops may be a serious problem to satellite communication at short wavelengths when dual - polarized signals are employed. This study investigates the effects of rain induced depolarization on circularly polarized millimeter and centimeter wave propagation in a tropical location (Nigeria). Propagation along the Earth-space path is considered. Cross-polarization discrimination (XPD) and copolar attenuation (CPA) are calculated for an effective raindrop canting angle of 10° with standard deviation of 19° and for varying elevation angles. Three tropical rain types classified as widespread, shower and thunderstorm are assumed. The frequency range of the study covers the band 4-100GHz. The study presents results for the variation of XPD with frequency, path length to the rain region, XPD as a function of fade depths (CPA) and so on. The study found that for convective rain types (shower and thunderstorm) cross polarization discrimination becomes very poor as elevation angle decreases and frequency and rain rate increases. For instance, as elevation angle becomes low (e.g. 23°), because the path length to the rain region becomes longer, XPD falls rapidly with increasing rain rate. Copolar attenuation on the other hand increases with increasing rain rate and frequency. The study also found that depolarization of circularly polarized waves is more severe when signal transmission is through convective rain type. vii.: 59p.: ill.; 32cm.

2004-02-04T00:00:00Z OMEHE, NNAMDI NKEMDIRIM NNAMDI NKEMDIRIM http://196.220.128.81:8080/xmlui/handle/123456789/5813 2026-04-10T10:43:12Z 2006-12-14T00:00:00Z

DESIGN AND CONSTRUCTION OF A CONCENTRATOR TYPE SOLAR COOKER OMEHE, NNAMDI NKEMDIRIM NNAMDI NKEMDIRIM ABSTRACT A concentrator type solar cooker has been designed and constructed. The concentrator is made up of two concentrating systems: a spherical dish and a reflector field. The spherical dish consisted of segmented plane mirrors while the reflector field consisted of an array of plane mirrors mounted on individual stands. The data were collected at the observatory of the Department of Meteorology, Federal University of Technology, Akure (7. ISDN, 5.050E). Data collected include, water temperature (the content of the pot), air temperature; wind speed and insolation. The time interval for data collection was 1 minute. The average is taken for 10 minutes, this was done by a logger. But that of water temperature was done manually at an interval of five minutes, and the average taken over 10 minutes. The power of the cooker was found by multiplying the mass of water by temperature gain within the 10 minutes interval and dividing by 600 seconds, The results of the test Was 72.5 percent satisfactory. x.: 92p.: ill.; 32cm

2006-12-14T00:00:00Z ALADENIYI, AYODEJI http://196.220.128.81:8080/xmlui/handle/123456789/5812 2026-04-10T10:17:20Z 2007-07-09T00:00:00Z

DESIGN, CONSTRUCTION AND CHARACTERISATION OF CABINET SOLAR DRYER WITH STORAGE FACILITY ALADENIYI, AYODEJI A passive solar cabinet dryer with dimensions (0.909 m X 0.602 m X 0.601 m) was constructed using wood as the frame for the outside cover, while the inside was lined with foam as an insulator and Aluminum plate painted black was used as the receiver. A flat plate collector which was a double layered glass served as the uppermost covering. Solar thermal storage device was integrated with the dryer. The performance of the solar dryer was evaluated using plantain chips, pepper and fish. The drying inside the dryer was compared to drying in the open air. The drying process was done in six days. The amount of energy trapped or absorbed by the dryer was computed. Also, throughout the period under study, the temperature in the dryer was found to be higher than the ambient temperature. This gave the dryer a lot of advantage over the open air drying vii.: 72.: ill., 32cm

2007-07-09T00:00:00Z