Abstract The electronic, optical and thermal properties of hexagonal and cubic phases of Ge2Sb2Te5 (GST) have been calculated using density functional theory (DFT) as implemented in the QUANTUM ESPRESSO computer package. GST is successfully applied in optical memory such as rewritable CDs and is a promising candidate for non-volatile electronic memory. In optical storage, the reflectivity contrast can be optimized towards the ultraviolet spectral range, thereby increasing data storage capacit...
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 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...
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 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 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...
Abstract A modification of Biot's pornelastic differential equi~tionsis made to include nrarrix-fluid interaction mech~ismsw hich assume n solid-fluid relaxation hnction coiipli~igc c~eflicient. Vulucs of physical propcrtics of scdi~iicntsn .rc incorporuted'into cqilationswhicl~d cfinc phnsc yelocity nnd attei~uatibnf or pcirous media which are dependent on the co~~posidteen sities of various medin (silt, and lnediu~na nd coqfse sand). The results enable us to coinpare tlie .atenuation and ve...
ABSTRACT Ionizing radiations resulting from either natural or artificial radioactivity are useful but associated with them are health risks which increase with exposure. The natural radioactivity levels in soils of some locations in Jos and Abeokuta are significantly higher than the world average. Enhanced internal and external radiation exposures to man may result from physical presence in, and ingestion of food items grown in these areas. Scientific data are sparse on the radionuclide conte...
Abstract Thls artlcle introduces Monte Carlomethds which are duerent from conrentio~nl ~mieticanl lethods andshow bow some of the methods can be applled in Physlcs,ro simrclate or solve physical proble~its. thtwr~hco rrilvrrer ~vrgrrrr>rr' (wrltten In FORTRAN In thls ca.r@, by ruing a few cxnml~lrrt oltchinff ,n doi.11 arid c/ns.~l[:olI 'lr~!!:ricrsh r~t~.rrr~s ~g r~lrfihess. A functional approach to probab//ity and statisticscl is describeJJor the p,1rynre o/tbn work r*.st~nd of comp/eto tre...