Scholarly works

Permanent URI for this collectionhttps://repository.ui.edu.ng/handle/123456789/420

Browse

Now showing 1 - 20 of 75

INITIAL STAGES AND SOME CHARACTERISTICS OF WEST AFRICAN LINE SQUALLS
(1983-03) ADEDOYIN, J. A.
A review of West African synoptic weather pattern reveals that the sub-region experiences a special kind of atmospheric disturbance -the line squall - whenever the south-westerlies cover, approximately, the whole of Nigeria. Various methods that have been used to study the squalls (i.e. observational investigations, satellite investigations and modelling) have not been very successful in isolating the trigger mechanism of the phenomenon. It is been proposed that line squalls are initiated through the amplification (with time) of any wave-like perturbation along the surface of discontinuity between the south-westerlies and the north-easterlies. The amplifying perturbations could block the 650 mb. mid-tropospheric jet which further distorts the 'bump' formed by the undulating perturbation. This distortion forces the southwesterlies further up and they could condense. The precipitates fall into the underlying, dry jet and some of them evaporate; the latent heat of evaporation being supplied by the jet. The jet, now cooler, sinks. On sinking, the jet could hit the surface of the earth on which it forms the squall front and crawls; thereby lifting the south-westerlies ahead of it. The cycle of condensation, evaporation and sinking then continunes. A gravity-wave model of this mechanism is presented through the solution of a frequency equation with the aid of a two-layer atmospheric model. The solution is an eigenvalue problem from which many modes of different growth rates and phase velocities could be obtained. Some of these phase velocities will be complex - the real part representing the phase velocity while the imaginary part represents the amplification. Waves with the largest amplifications (i.e. the largest imaginary part) are those that could possibly block the 650 mb. mid-tropospheric jet and trigger off line squalls. Among others, this proposal on the trigger mechanism of line squalls is able to explain: (i) the preference of highlands as places of origin of line squalls, (ii) the close association between the speeds of propagation of line squalls and the mid-tropospheric jet and (iii) the observed overturning of the atmosphere after the passage of line squalls.
SPIN COMPLEXES IN FERROMAGNETISM
(1988-11) AGBOOLA, A. I.
The spin-wave theory in Heisenberg model of ferromagnetism is investigated with the Holstein - Primakoff transformation and with emphasis on the spin wave interactions. The temperature Tₒ below which the concept of magnons is valid is determined. By a special expansion formalism of operator (l-a+a/2S)1/2 which yields 1+(1-(1-1/2S)1/2 )a+a it is shown that quantized spin waves which behave like spin 1 quasiparticles (with dispersion relation ω~ k2 ) called magnons at temperatures T < Tₒ, are Bosons with an effective (negative) electrochemical potential µ that varies as T in the wave-wave interaction approximation. The various coefficients of Tv in the expression of the spontaneous magnetization M(T)/M(o) = l-(C1T3/2+C2T5/2+C3T7/2+C4T4) as well as the specific heat for some ferromagnets are calculated. The results are remarkably close to the experimental values obtained by other investigators. The method used enables one to deal especially with regimes of small spin values S for which µ differs substantially from zero. The influence of the chemical potential on some thermodynamic quantities are found for ferromagnets with Hexagonal-close-packed structures, as well as for cubic crystals, The existence of the spin wave interactions and hence of non-zero effective chemical potential is shown to give rise to a lowering of the thermodynamic internal energy with the implication that spin waves, on the average, form bound states called spin complexes. The kinematical as well as the dynamical interactions on the thermodynamic quantities are also found for some ferromagnets, by subjecting the magnons to intermediate statistics. The influence of the spin-wave-spin-wave-spin-wave interactions on the coefficients of Tv in the expression of the spontaneous magnetization of some ferromagnets are found to be negligible in comparison with wave-wave interactions. An attempt is made to extend the above calculations to spin complexes in antiferromagnetism, a phenomenon which seems to be relevant to high temperature superconductivity.
Modelling effective rheologies for viscoelastic porous media with application to silt, and medium coarse sand
(Nanjing Institute of Geophysical Prospecting, 2004) Olowofela, J. A.; Adegoke, J. A.
A modification of Biot's poroelastic differential equations is made to include matrix-fluid interaction mechanisms which assume a solid-fluid relaxation function coupling coefficient. Values of physical properties of sediments are incorporated into equations which define phase velocity and attenuation for porous media which are dependent on the composite densities of various media (silt, and medium and coarse sand). The results enable us to compare the attenuation and velocities of waves in these media. We observed that the density of coarse sand is greater than that of medium sand and this in turn is greater than that of silt-the same holds-for the velocities of P-waves in these media but the situation is converse for shear waves in the same given media. As the densities of the media increase, their attenuation decreases as it was found that the attenuation of silt is the highest and that of coarse sand lowest for the media considered.
Contemporary aspects of Monte Carlo methods and simulation in physics
(Faculty of Science, University of Abuja, 2004) Olowofela, J. A; Adegoke, J. A; Adewumi, O. P; Kamiyole, I. C.
"This article introduces Monte Carlo methods which are different from conventional numerical methods and show how some of the methods can be applied in Physics to stimulate or solve physical problems, through computer programmes (written in FORTRAN in this case) by using a few examples touching modern and classical physics showing its usefulness. A functional approach to probability and statistics is described for the purpose of this work instead of complete treatment. The importance of good sequence of random numbers with large periods is demonstrated and the methods, in same instance are compared with conventional type and differences pointed out. "
Effects of clay content and porosity on wave velocities in unconsolidated media wing empirical relations
(Nanjing Institute of Geophysical Prospecting, 2004) Olowofela, J. A.; Kamiyole, I. C.; Adegoke, J. A.
"Wave velocities in sandstones are greatly influenced by porosity and clay contents. We formulated new empirical relations for the velocities Vp and Vs in these media which take into account the porosity and clay contents. These relations are Vp=5.57 - 6.47ø - 2.27C1 ø and Vx=3.41 - 4.44ø - 2.23C1 ø, and can be used to compute velocitiesfor various porosities and clay contents. The result compare favourably with those of other works. "
A laboratory study of the effects of porosity and bed tilting on the discharge rate of groundwater
(Springer India, 2005) Olowofela, J. A.; Adegoke, J. A.
The study of movement of underground water helps to predict the extent of flow in as much as we can determine the volume rate among other things. Sand samples from river bed were used as porous media, a laboratory experiment was set up to look at longitudinal dispersion in term of volume of liquid flowing across a unit cross sectional area per unit time in these materials. Water was made to flow through a cylindrical pipe drilled sideways at intervals. Values of pressure were taken at regular interval and using appropriate basic equations, the volume flux rate was determined at various angles of tilt, from which volume rate of flow was also determined. A graph of volume rate of flow against angle of tilt gives the value of volume rate of flow as 1.00 ' 10-10 m3/s irrespective of porosity and permeability of the medium provided that the angle of tilt is 1.42°
An algoritm for solving electromagnetic field equations by finite element method
(Medwell Journals, 2007) Adetoyinbo, A. A.; Adewole, O. O.
Describing the behaviour of electromagnetic frequency responses from vertically inhomogenous and anisotropic earth of 2-Dimensional structures energized finite sources is computationally laborious. Differential equations were derived and their numerical solutions also sought for the desired components of electric and magnetic fields. Also, expressions for the impedance and apparent conductivity were stated. An algorithm based on the finite element method for computing approximate numerical solutions for these problems were dealinated.
Effect of porosity on surface of drawndown in an unsteady state drainage in porous material. I
(2007) Olowofela, J. A .; Adegoke, J. A; Bejide, F. A.; Okeyode, I. C.
"This work considered the unsteady state drainage of fluid from a vertical column of porous material of varying porosities in an attempt to verify variation of drawndawn surface with porosity and time using riverbed sand. Kerosene was used as the flowing fluid. Mathematical assumptions ware made in connection with Darcy's law. The result showed that the experiment which was designed from the theoretical framework agreed with the theory to a large extent, However, this is not in perfect agreement with an earlier experiment which was performed using well rounded beads in which glycerine was used as the flowing fluid. A FORTRAN program was written to study the variation theoretically and this was compared with the experimental result. There exists, a degree of discrepancy between theory and experiment indicating that, the mathematical formulations did not perfectly agree with the complex earth system as compared with the bead model that was initially used. There is a need for the modification of the mathematical formulations; nonetheless, an unsteady drawndown, pattern was attained with different porosity even in medium with very complex geometry. "
Modification of Darcy's law for turbulent flow in saturated porous media
(Medwell, 2007) Popoola, O. I.; Adegoke, J. A; Alabi, O.
"Darcy's law is an essential equation in determining the permeability of porous media which is vital tool in seepage and drainage control in soils. However, whenever the aggregate sizes of the porous media and hydraulic gradient are large, the flow in drains will be semi-turbulent to turbulent. This research aims at modifying the true Darcy's permeability determined under small hydraulic gradients that ensure laminar or nearly laminar flow to allow for reduced efficiency caused by turbulence at greater hydraulic gradient and provide a relation between the maximum gradient for laminar flow and porosity of the porous media. A modeled experiment was set up using sand samples of different porosities from riverbed as porous media, which were packed in a vertical transparent cylinder tube of diameter 1.85x102m and relative permeabilities were determined for gradient ranging from 1.15-15.00. The result of the experiment shows that relative permeability increases with increasing porosity but decreases with increasing gradient. The maximum (or limiting) hydraulic gradient for laminar flow decreases with increasing porosity. Also, the vertical fluid flow in any porous medium is laminar or nearly laminar as much as hydraulic gradient is less than or equal to 1.04. "
Monitoring the effect of water pollution in twelve selected water dams in Osun State of SouthWestern Nigeria
(2007) Adegoke, J. A.; Sunmonu, L. A.; Lateef, T. A.
"The level of water pollution by heavy metals (Cu, Zn,Co, Ni, As, Mn, Cd, Cr, Pb) in twelve selected water Dams in Osun state were determined in order to know their distribution and possible source into the dams. Their bottom sediment and water were collected for analysis. The result in sediment showed that the concentration of manganese is high in all the dams with values ranging from 21, 27-775.99mg/kg and it spreads across all the locations. Cobalt was detected only at one location with concentration of 3.01md/kg. The result in water analysis showed that the concentration of zinc is more than that of manganese, almost in all the dams. The values detected were between 0.0618lng/kg and 0.5068mg/kg while that of manganese was between 0.011 2mg/kg and 0.1887 mg/kg. Cobalt and cadmium were not detected in all the dams. The variation in the concentration of these metals in sediment and water may be due to chemical factors such as solubility, ion exchange ratio and electrochemical deposition. The concentrations of all metals detected were below the standard limit for the heavy metals in surface water according to Regulatory authority Specification. Meanwhile, bioaccumulation of these metals in tissue of the body may be toxic to human health. "
Study of permeability of saturated homogeneous and heterogeneous porous media
(Duncan Science Company, 2008) Popoola, O. I.; Adegoke, J. A.; Alabi, O. O.
Many practical seepage and drainage problems can be studied by constructing flow nets for section with a single permeability, however, many natural soil deposits are more or less stratified, often with horizontal bedding that make horizontal permeabilities much greater than the vertical. Three different types of heterogeneous media from five soil sample of different porosities were considered: with constant-head permeameter to determine the saturated hydraulic conductivity for each. The result shows that least permeable medium dominates in the permeability of heterogeneous medium than layered heterogenous medium. However, fluid flow in homogeneous porous media is generally faster than that of heterogeneous medium of similar geometry and grains packing. Therefore, the effect of least permeable unit in heterogeneous medium must be considered in selecting a proper filter for seepage control.
Variability of permeability with diameter of conduit
(Indian Academy of Sciences, 2008) Adegoke, J. A.; Olowofela, J. A.
"An entry length is always observed before laminar flow is achieved in fluid flowing in a conduit. This depends on the Reynolds number of the flow and the degree of smoothness of the conduit. This work examined this region and the point where laminar flow commences in the context of flow through conduit packed with porous material like beads, of known porosity. Using some theoretical assumptions, it is demonstrated that permeability varies from zero at wall-fluid boundary to maximum at mid-stream, creating a permeability profile similar to the velocity profile. An equation was obtained to establish this. We also found that peak values of permeability increase with increasing porosity, and therefore entry length increases with increasing porosity with all other parameters kept constant. A plot of peak permeability versus porosity revealed that they are linearly related. "
Analysis of heavy metals concentration in sediments and water samples of selected functional dams in Oyo State, Southwestern Nigeria
(2008) Adegoke, J. A.; Sunmonu, L. A.; Ojeniyi, O. S.
"The quality as well as the quantity of clean water supply is of vital significance to the welfare of mankind particularly in the developing countries. Therefore, knowing the concentration of heavy metals present in Dams can help us to ascertain the health safety of the populace using the water for drinking and domestic purposes. Ten Dams at Oyo State in the Southwestern Nigeria were studied for the heavy metals concentration contained in the sediments and water of the selected Dams. Bottom sediments and water were collected from the selected dams for analysis. Analysis of both the water and sediments to determine the concentration of each heavy metal was evaluated. The result obtained shows that, the concentration of Manganese (Mn) ranges from 14.8 mg/kg to 332.96 mg/kg followed by Zinc (Zn) which ranges between 6.18 mg/kg and 52.53 mg/kg which spread across all locations., Lead (Pb) was not detected in virtually all the locations except in Ilora which has a concentration of 0.87 mg/kg and this may be as a result of the activities of motor mechanics and vulcanizers around the dam. In the water samples, the result showed that the concentration of heavy metals is very low which is far below the limit specified by World Health Organization (WHO). Zn has the highest concentration ranging from 0.049mg/kg to 0.729mg/kg, followed by Mn which has concentration between 0.011mg/kg and 0.344mg/kg. Pb, Cadmium (Cd) and Cobalt (Co) were not detected at all in all the water samples. The variation in the concentrations may be due to geological nature of the ground, solubility, an ion exchange and human activities. "
Open land dumping: an analysis of heavy metals concentration of an old Lead-battery dumpsite
(2009) Adegoke, J. A.; Owoyokun, T. O.; Amore, I. O.
"Use of open land as dump sites by the manufacturing industries in developing countries without appropriate prevention of environmental hazards has resulted in prominent levels of waste and disposal effluents. This has resulted in the contamination of soil and the exposure of human populations to environmental and health hazards. This study focused on the investigation of soil contamination by heavy metals via waste disposal of a lead battery factory in Lalupon, Oyo State, Nigeria. Composite samples obtained from nine sample locations were digested with concentrated acids (HN03, HC104 and HF) and filtered. The filtrate obtained was analyzed for seven different analytes (Cu, Cr, Pb, Zn, Cd, Ni, and As) using atomic absorption spectroscopy (AAS). The lead content exceeded maximum allowable concentrations, MAC (100 ppm), in all points. Copper content was above MAC (50 ppm) in a majority of the points. Cd exceeded MAC (0.3 ppm) in just one point. The study shows that the soil in the old dump site has been contaminated heavily with Pb and Cu. "
Natural radioactivity and hazard assessment of imported ceramic tiles in Nigeria
(2009) Ademola, J. A.
The natural radionuclides (226Ra, 232Th and 40K) content of ceramic wall and floor tiles commonly used in Nigeria have been determined by a gamma ray spectroscopy system using a high purity germanium detector. The activity concentrations of 226Ra, 232Th and 40K ranged from 52 ± 2 to 105 ± 3, 56 ± 1 to 115 ± 2 and 185 ± 9 to 893 ± 17 Bq kg-1 with mean values of 72 ± 14, 84 ± 18 and 629 ± 198 Bq kg-1, respectively for the wall tiles. For the floor tiles, the activity concentrations of 226Ra, 232Th and 40K varied from 41 ± 2 to 131 ± 4, 59 ± 1 to 127 ± 2 and 351 ± 11 to 979 ± 16 Bq kg-1 with mean values of 74 ± 31, 82 ± 24 and 618 ± 231 Bq kg-1, respectively. The errors quoted in the means are standard deviations. The values of radium equivalent activity (Raeq) calculated varied from 194 to 328 Bq kg-1 for the wall tiles, and 176 to 306 Bq kg-1 for the floor tiles. The radium equivalent activities of all the samples examined were lower than the recommended limit of 370 Bq kg-1 for building materials. The mean values of the external hazard index (Hex), the activity index (Iγ) and the alpha index (Iα) of the wall and floor tiles are less than unity, which is a commonly accepted limit.
Modification of fluid flow equation in saturated porous media
(Bachudo Science Ltd, 2009) Alabi, O. O.; Popoola, O. I.; Adegoke, J. A.
Experimental investigations have shown that variation of porosity and hydraulic gradient are responsible for the deviations from Darcy's law, which is perfectly obeyed only when the fluid flow is laminar in porous media. Previous attempts to modify this equation considered only the effects of porosity of surface-active materials such as clay in causing deviations from Darcy's law. In this study, both the effect of porosity of any porous medium and hydraulic gradient from recent experimental data were considered. A general equation for both laminar and non-laminar or turbulent fluid flow in porous media at any hydraulic gradient is proposed, including the boundary conditions.
The effects of porosity and angle of inclination on the deflection of fluid flow in porous media
(Bachudo Science Ltd, 2009) Popoola, O. I.; Adegoke, J. A.; Alabi, O. O.
"The movement of contaminated fluid from a solid waste landfill into a portable water aquifer located beneath is an example of unwanted underground flow with the problem of limited portion of land available for building construction in the cities, coupled with the rise in price of good and accessible land, there is a need for quick and urgent solutions to environmental pollution that may be resulted from this problem. In this research, a laboratory setup consisting of a big transparent cylindrical pipe 108 5cm long with radius 2 23cm was used as inlet pipe and five small equal transparent cylindrical pipes with radii 0.03cm were used as outlets, which were joined to the circular plastic plate on the top of the inlet pipe at different angles ranged from 0° to 90° from a normal point. The inlet pipe and outlets pipes were filled with samples of soil of different porosities and titled at different angles of inclination. The volume of water discharged was measured directly with measuring cylinder from the set-up in each case. The volumetric flow rate and volume flux were computed from the values of volume discharged. These were done in order to determine how the arrangement of porous material of different porosities with a particular angle of inclination can influence the deflection of fluid flow from its linear direction. This is sequel to its practical applications in designing a construction with a cross-section of soils in deflecting contaminated fluid from septic tank to different directions from the source of water within the same small portion of land. It was observed that angle of inclination does not have a significant effect on the deflection of fluid but volume flux increases with increasing angle of inclination. Also, the greater the difference in the porosity of the cross-section of the media in which the fluid is flowing the greater the volume flux However, the most suitable arrangement of cross-section of soils for deflection of fluid at higher angle from normal is when it flows through a medium of low porosity to that of higher porosity. "
Evaluation of heavy metal status of water and soil at Ikogosi warm spring, Ondo State Nigeria
(Department of Geography and Enivironmental Studies and Management, Bahir Dar University, Ethiopia, 2009) Adegoke, J. A.; Agbaje, W. B.; Isaac, O. O.
The concentration levels of selected heavy metals, (Cu, Cd, Zn, As and Cr) were determined in the soil (ug/g) and water (ppm) samples collected at Ikogosi Warm Spring, Ekiti State, Nigeria. After digestion, Atomic Absorption Spectrophotometer (AAS) was employed for the determination. The study area was at Latitude of 7° 35' 38.9'' Longitude of 4° 58' 52.6'' and at average elevation of 479m above mean sea level (msl). The average concentrations (ug/g) of the heavy metals in the soil are Cu (5.29), Cd (1.50), Zn (46.72), As (10.50) and Cr (339.78). The average concentrations (ppm) of the heavy metals in the water are Cu (4.8), Cd (0.15), Zn (4.17), Ar (0.57) and Cr (1.46). The mercury was below detection limit for both soil and water samples. In the overall, the average concentration of chromium is the highest in the soil with concentration of 339.78 ug/g (an average of 84.27%) and cadmium having the lowest with value of 1.50 ug/g (an average of 0.37%). When average concentration of heavy metal in the water was considered, copper had the highest level with concentration of 4.80ppm (an average of 43.01%) and cadmium had the lowest concentration with value of 0.15ppm (an average of 1.43%). Comparison of these results showed that, their mean levels are within the standard values obtained in Nigeria and some developed countries.
The effects of porosity and angels of inclination on the deflection of fluid flow in porous media
(Medwell Journals, 2009) Popoola, O. I.; Adegoke, J. A.; Alabi, O. O.
"The movement of contaminated fluid from a solid waste landfill into a portable water aquifer located beneath is an example of unwanted underground flow. With the problem of limited portion of land available for building construction in the cities, coupled with the rise in price of good and accessible land, there is a need for quick and urgent solutions to environmental pollution that may be resulted from this problem. In this research, a laboratory setup consisting of a big transparent cylindrical pipe 108.5cm long with radius 2.23cm was used as inlet pipe and five small equal transparent cylindrical pipes with radii 0.03cm were used as outlets, which were joined to the circular plastic plate on the top of the inlet pipe at different angles ranged from 00 to 900 from a normal point. The inlet pipe and outlets pipes were filled with samples of soil of different porosities and titled at different angles of inclination. The volume of water discharged was measured directly with measuring cylinder from the set-up in each case. The volumetric flow rate and volume flux were computed from the values of volume discharged. These were done in order to determine how the arrangement of porous material of different porosities with a particular angle of inclination can influence the deflection of fluid flow from its linear direction. This is sequel to its practical applications in designing a construction with a cross-section of soils in deflecting contaminated fluid from septic tank to different directions from the source of water within the same small portion of land. It was observed that angle of inclination does not have a significant effect on the deflection of fluid but volume flux increases with increasing angle of inclination. Also, the greater the difference in the porosity of the cross-section of the media in which the fluid is flowing the greater the volume flux. However, the most suitable arrangement of cross-section of soils for deflection of fluid at higher angle from normal is when it flows through a medium of low porosity to that of higher porosity. "
Radiogenic heat production distribution of soil samples from Idi Omo, Akinyele LGA, Oyo State, Nigeria
(Creative Commons Attribution, 2009) Adegoke, J. A.; Layade, G. O.; Popoola, O. I.
The NaI(TI) gamma-ray spectrometer was employed to determine the concentration of naturally occurring Potassium(K-40). Uraniurn (U-238) and Thorium (Th-232) vis-à-vis the radiogenic heat production in soil samples from Idi-Omo farmland area of Akinyele, Local Government area o f Oyo state. The farmland which is at Latitude 07° 30’ 26.3" and Longitude 003° 57' 21.9" covers an area of about 80,000 square metre, and is at an average elevation of 240m above mean sea level (msl). The samples were pulverized, sealed and activities of the radiogenic isotopes in them were measured for an accumulating period of 7 hours (25200s). The elemental concentrations were determined from the gamma ray spectra. The radiogenic heat determined from activity concentrations on samples from the locality for 40k has on the average 92.86±0.02p W/Kg, while 238U has 251.26±0.61pW /Kg and 232Th has 77.210±0.03pW/Kg. The mean radiogenic heat calculated from the three radionuclides for the whole area under study is 421.3.3±0.66pW/Kg. 238U contributes 60% to the total heat production, 40K contributes 22% and 232Th contributes 18%. This makes Uranium to be the highest contributor to the total heat production in the area. However observed that the radiogenic heat production distribution in the area is low.