Abstract This work comprises of several aspects of calcium-aluminate phosphor activated with rare earth metal ions i.e. (CaAl2O4:Eu2+, Nd3+, and Dy3+). In particular the luminescent and structural properties of the long afterglow CaAl2O4:Eu2+,Nd3+,Dy3+ phosphors prepared by urea-nitrate solution-combustion method were investigated. The solution-combustion method is more efficient because phosphors with high efficiency were obtained at low temperature (500 oC) in a very short period of time (5...
ABSTRACT Inflation is a period of an accelerated expansion of the universe. Cosmological perturbations are created by the amplification of quantum vacuum fluctuations of matter and metric perturbations during inflation. The equation of dynamics governing the evolution of cosmological perturbations within the cosmological model in a single field inflationary scenario takes the form of a standard non-linear second-order differential equation, whose exact analytical solution has not been obtaine...
ABSTRACT Rastrineobola argentea, (R. argentea) is a commercially important fish species in Lake Victoria, with a characteristically smaller size compared to the other fish and high surface moisture content. However the prevalent preservation method of the fish is open sun drying, in which the fish is laid uncovered on the ground for a prolonged period exposed to; contamination, attack by bacteria, molds, rodents, birds and adverse weather conditions. Often huge losses estimated at between 20 ...
ABSTRACT With the progressive decline of capture fisheries and human population upsurge worldwide, aquaculture is expected to play a great role in ensuring sufficient fish in the market. Thus, aquaculture is promoted by world food production agencies and governments, and has experienced significant growth. However, for African countries such as Kenya, aquaculture production is disproportionately lower than capture fisheries. Thus, there is urgent need to improve aquaculture production in thes...
Abstract Measurement of equatorial ionospheric absorption made by the A3 Method for quiet conditions near a period of maximum solar activity (1979 to 1981) are used for a detailed examination of Absorption of Radio Waves in equatorial Ionosphere. Assuming an index law of the form L. 1.Cos"for the absorption (x being zenith angle of the sun). the diurnal and seasonal characteristics of the variation are obtained for two frequencies (4.9 Mhz and 7.1 MHz) and compared with existing theories. Pro...
ABSTRACT Despite many buildings have fire fighting systems installed in them; many people are still losing their lives and properties due to fire accidents. In this research, an automatic cost effective device for the detection and control of fire has been designed and constructed. The system has an additional feature of sending signal to a pump/sprinkler through a relay. It is made up of two sensors, microcontroller, buzzer and a controlled fire fighting equipment (pump/sprinkler). LM 3...
ABSTRACT The earth‟s surface is affected by three main types of radiation from the sun: global solar (or total), beam (or direct), and longwave (or indirect) radiation. Global solar radiation is composed of direct and indirect radiation. Approximately 99% of the total radiation from the sun that reaches the earth is beam radiation, which has a wavelength range of 0.29 to 3.9 μm and is not subjected to interference from any interspatial matter. The remaining 1% is longwave radiation, which ...
Abstract This thesis discusses the development, design, fabrication and testing of spectrally selective beamsplitting absorption filters which can decouple quantum and thermal convertors to improve conversion of the total solar spectrum to useful energy.
Abstract Precipitable Water Vapour (PWV) is the amount of water vapour in the atmospheric column above a location equivalent to the amount of liquid precipitation that would result if all the water vapour in the column was condensed. Water vapour is the main source of opacity in the Earth’s atmosphere at infrared and millimetre to sub-millimetre wavelengths. The Event Horizon Telescope (EHT) is a large network of millimetre to sub-millimetre telescopes across the globe that is used to image...
We describe a novel and cost-effective method to enhance the photo-conversion efficiency of blended PbI2/TiO2 perovskite photovoltaic cells by pre-annealing the constituent film components during the fabrication. This approach is also unique because it does not presume a strictly controlled fabrication environment. The average conversion efficiencies of the cells of the final devices were observed to rise from 6.6% to 10.8% for annealing temperatures of 60 ◦C to 100 ◦C, respectively. Anne...
ABSTRACT Men‘s involvement in maternity care has been recognized as one of the key strategies in improving maternal health and accelerating reduction of maternal mortality. Men impact women‘s reproductive health through their role as partners, fathers and close family providers in terms of financial power and decision control they have. Factors that determine men‘s involvement in maternity care have been documented in other parts of the globe, but very little research has been conducted...
Abstract Twenty Concrete Blocks from (20) different Local Governments in Katsina state was measured using Gamma Ray Spectroscopy with NaI (TL) detector. Three naturally Occurring Radionuclides and their activity concentrations were determined, are 40K 226Ra, and 232Th. Their activity Concentrations ranges from 40K 46.11 ± 826.59 to 46.11± 8.55 Bq/kg, (226Ra) ranged from10.19 ± 2.43Bq/kg to 75.09 ± 4.98 Bq/kg and (232Th) ranged from 2.77 ± 9.59Bq/kg to 123.49 ± 9.35Bq/kg respectivel...
Abstract The High Energy Stereoscopic System (H.E.S.S.) is an array of imaging atmospheric Cherenkov telescopes located in the Khomas highlands of Namibia. Their primary purpose is to detect Cherenkov light (CL) produced by particles in extensive air showers which are produced by incident high energy particles (gamma rays or cosmic rays) on the Earth’s atmosphere. The array consists of four 107 m2 optical telescopes and a larger 614 m2 collective surface area telescope in the centre of th...
Abstract In this study, natural dye-sensitized solar cells (NDSSCs) were fabricated using crude and purified natural dye extracts aimed at investigating the effect of purified natural dyes on the dye-sensitized solar cell (DSSC) performance. Ethanol and methanol solvents were used to extract natural dyes from Senna singueana flowers, Senna singueana leaves, Ximenia caffra fruits, and Bougainvillea glabra bracts. Liquid-liquid extraction (LLE) method was used to purify the ethanol and methano...
ABSTRACT Radiation exposure during diagnostic X-ray examinations has been widely reported as one of the sources of cancer induction. Information on X-ray machine and exposure parameters are crucial to risk assessment, which in turn are important for optimization of radiation protection measures. The documentation of radiation risk in Nigeria is sparse and hence the effectiveness of radiation protection measures at diagnostic centres has not been well established. This work was aimed at measur...