Physics
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Item A review of the bulk layer pollutant transfer over Nigeria during the harmattan season(2007) Oladiran, E. O.,; Nymphas, F. F.A review of the results of the bulk characteristics of the harmattan dust is presented to facilitate ease of reference and regional comparison where similar local effects exist. The meteorological interconnections are dealt with. The transport properties are presented, and are found to agree with the plume model for cascaded continuous sources on a 1km x 1km gnd point system. The wind profile is found to be consistent with turbulent electrode model of Willet.Item A statistical approach to estimate wind speed distribution in ibadan, nigeria(2016) Rauff, K.O; Nymphas, E.F.In this paper, the wind energy potential in Ibadan is statistically analyzed using daily wind speed data for 10 years (1995-2004) obtained from the International Institute of Tropical Agriculture (IITA) and 1 year (2006) obtained from Nigeria Micro-scale Experimental (NIMEX) Ibadan,Nigeria. The statistical wind data set was analyzed using Weibull distributions in order to investigate the Weibull shape and scale parameters. The daily, monthly, seasonal, and yearly wind speed probability density distributions were modeled using Weibull Distribution Function. The measured annual mean wind speed was found to be 0.76 m/s and the total extractable wind power has been estimated as 0.33 kW at IITA while the annual mean wind speed ranged between 0.74 m/s, 1.02 m/s, 1.16 m/s and 1.34 m/s at (3 m, 6 m, 12 m and 15 m) respectively at NIMEX. The maximum extractable annual wind power density value of 0.90W /m2 for the whole year at IITA and 5.61W / m2 at the highest height of 15 m at NIMEX indicated that, Ibadan can be classified as a low wind energy region and it belongs to the wind power class 1, since the density is less than 100W /m2 . It is concluded that at both sites, the highest wind speed that prevailed in Ibadan is March and the location can be explored for wind power.Item 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.Item An artificial neural network estimation of global solar radiation at Ibadan, Nigeria using meteorological data(2020) Nymphas, E.F.; Udomboso, C.G.This paper estimates global solar radiation (Rs) from routinely measured meteorological parameters in the city of Ibadan, Nigeria, using artificial neural network method. Six combinations were used to estimate Rs namely (i) daily mean air temperature (T) and day of the year as inputs and global solar radiation as output, ((ii) daily mean relative humidity (RH) and day of the year as inputs and Rs as output (iii) daily mean T, daily mean RH and day of the year as inputs and Rs as output (iv) daily mean minimum relative humidity (RHmin) and day of the year as inputs and Rs as output, (v) daily mean minimum temperature (Tmin), daily RHmin and day of the year as inputs and Rs as output (vi) daily mean maximum temperature (Tmax), daily mean Tmin, daily mean RHmin, daily maximum relative humidity (RHmax) and day of the year as inputs and Rs as output. The neural network was trained with 3653 measured data between 1995 and 2004 and tested with data for 731 days between 2003 and 2004. The data for testing the neural network were not used for the training. The results obtained showed that the combination of RHmin, RHmax and day of the year gave the best estimate of Rs with MSE of 3.4124. This is followed by RHmin and day of the year with MSE of 3.4424. Daily mean air temperature and day of the year could not mimic the measured Rs; it gave MSE of 5.3345. It is concluded that Rs can be estimated for locations where only temperature and relative humidity data are available.Item Analysis of data on net longwave, shortwave, and global radiation during a transition period in a tropical station in southwestern Nigeria(2009) Ogolo, E.O. Ph.D,; Falodun,S.E.; Oluyanmo,S.S.; Nymphas, E.This paper examines the distribution of the surface radiation balance components measured during the Nigerian Micrometeorological Experiment (NIMEX-1), a field study conducted to measure surface heat fluxes in the boundary layer during the transition period which marks the end of dry season and the onset of wet season (February 15 and March 10, 2004) in the southwestern part of Nigeria. Regression equations were obtained using the daily average values and hourly mean values between net shortwave and net longwave radiation, respectively, with the global radiation. Higher correlations with low standard error of measurement were obtained for daily mean values than the hourly mean. It was also observed that the peak values of each type of radiation during the period occurred, on average, two hours after noon when it was expected to occur.Item 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. "Item Assessment of building failure within and around quarries(2019-07) Adetoyinbo, A. A.The substructures of various engineering structures that were erected on the earth are being were been supported by the soil. Hence, the nature of the soil supporting these structures becomes an important issue. Quarry blasting peak particle velocity (QBPPV) is not sufficient to ascertain the causes of foundation failure, therefore, the physical parameters governing the competency of the soil supporting engineering structures need to be determine. This work investigated the possible causes of foundation failure of buildings within the vicinity of quarries. The investigation was done by carrying out Vertical Electrical Sounding (VES) and Radial Vertical Electrical Sounding (RVES) using Campus omega terrameter. The results show that buildings found within this area have shallow foundation and their foundations founded on sandy clay which can still support foundation The values of the degree of fracturing was found not to exceed 1.53 in this region which was not the case with the previous radial vertical electrical soundings, 1.94 was calculated as the highest degree of fracturing for RVES 1 while 1.83 was calculated for RVES 2. In all the RVES, degree of fracturing ranges between 1.02 to 1.94.Item Assessment of Detrimental Health Effect of Radiation Associated with Diagnostic X-Ray Examinations at Four Centres in Nigeria(2011) Akinlade, B. I.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 measuring effective dose received by patients during diagnostic x-ray examinations and estimating the associated risk. Between the years 2004 and 2006, the beam output of x-ray machines at four diagnostic centres with adequate regulatory activities were measured with non-invasive x-ray meter. These centres include University College Hospital (UCH) Ibadan, Twotees Diagnostic Centre (TDC) Ibadan, Obafemi Awolowo University Teaching Hospital Complex (OAUTHC) Ile-Ife and National Hospital Abuja (NHA). Field sizes, focus to skin distance (FSD), tube filtration, operating potential (kVp) and tube loading (mAs) were measured and used to calculate Dose Area Product (DAP) per patient. Data on age and examination type were recorded for 1034 patients which include 310(UCH), 276(TDC), 220(OAUTHC) and 228(NHA). These and calculated DAP were used to run Monte Carlo program to obtain effective dose. The risk of cancer was thereafter estimated using fatal cancer risk factor of 5 x 10-2 Sv-1. The results obtained were compared with the risk estimates recommended by the International Commission on Radiological Protection (ICRP). X-ray field sizes and FSD of the examinations considered ranged from 8 cm x 5 cm to 40 cm x 35 cm and 75 cm to 139 cm respectively. The tube filtrations (mmAl) at UCH, TDC, OAUTHC and NHA were 1.7, 2.7, 1.7 and 1.0 +1.0 mmCu respectively while the mean exposure parameters (kVp, mAs) were 69, 45; 76, 79; 100, 83; and 75, 28 respectively. Analysis of examination type showed that thoracic x-ray examination was the most common (74.0%). This was followed by head and neck (11.0%), pelvic (8.0%), lower limb (4.0%), abdomen (2.0%) and upper limb (1.0%). The mean age (years) of patients was 38±1 at UCH, 32±1 at TDC, 27±1 at OAUTHC and 28±1 at NHA. Examination procedures were the same in all centres except the use of anti-scatter grid for thoracic examination at OAUTHC. In all x-ray examinations, DAP (mGycm2) generally ranged from 70 to 38,155. The range of effective doses (mSv) at UCH, TDC, OAUTHC and NHA were 0.01–0.11, 0.01–0.17, 0.24–4.74 and 0.01–0.10 respectively while the corresponding estimated risks of cancer per million were 2–9, 2–22, 100–400 and 2-6. The values at OAUTHC were higher than ICRP risk estimates of 35 cancer cases per million. This was traceable to selection of high kVp with high mAs and insufficient tube filtration. Radiation risks associated with diagnostic X-ray examinations were within acceptable limit except at OAUTHC. For radiation risks to be within the recommended limit, the use of high kVp with low mAs and careful application of anti-scatter grid are encouraged.Item Assessment of ground water pollution in Itagunmodi, South-West, Nigeria(2012-02) Adetoyinbo, A. A.; Bello, A. K; Hammed, O. S.Some investigations have been earned out on geochemical characteristics of soil samples that embedded the ore deposits. Physiochemical analysis of water collected within gold mining area and the water consumed in the town of Itagunmodi was earned out to determine their hygienic conditions. The major objective of this study was to determine the suitability of the available water consumed in the town based on the Physiochemical analysis test carried out. In this regards, four major sources of water were analyzed. Analysis shows that the water within the town of Itagunmodi was hygienic with the inclusion of water within the mining site. The analysis includes; conductivity test, the pH test and others. It was noticed that the pH of the sample from the gold mining site was also suitable for drinking according to the World Health Organization standard. For a safe drinking water, the pH should be between (6.5 -8.5).Item Assessment of groundwater quality in unconsolidated sedimentary coastal aquifer in Lagos State, Nigeria(Academic Journals, 2009-04) Adebo, B. A; Adetoyinbo, A. A.This study assesses the quality of ground water from nine different borehole locations in Lagos State, Nigeria. Borehole water samples were carefully collected for physico - chemical analyses. Calcium, magnesium, iron, zinc, copper, manganese, aluminium, and silver, Nitrate, phosphate, fluoride, chloride, pH, conductivity, total dissolved solid, total suspended solid, hardness, summation of ions as well as the temperature and colour were assessed among the entire samples collected. The results show that: temperature ranges from 26.6 - 27.8°C, pH (7.27), average conductivity (462.2 ps/cm), TDS (204.73 mg/l), Total hardness (18.48 - 297.70 mg/l) and Chloride concentration (343.3 mg/l). However, a high value of chloride, 343.3 mg/l, was recorded in one of the water sample collected but, this is higher and above the limit of WHO guidelines of portable water (250 mg/i). This may be due to the proximity of the area where the sample was collected to the sea. Five samples of the water are is soft, that is, hardness was within a range of 0 - 75 mg/l recommended for safe drinking water, one is moderately hard while three samples are hard. Also, the presence of metals such as zinc, manganese, sodium, copper and magnesium were also observed. Results show that not all the water samples are safe for drinking purposes.Item Behavior of multiple lightning dischargers under a tropical thundercloud(2010) Nymphas. E.F.; Adeniyi, M.O.; Oladiran, E.O.Lightning discharges on ground depend on the electrostatic charges, nature of vegetation, topography and dynamics of the turbulent layer. In designing lightning protectors, one major consideration is the highest point in the surrounding that lightning is directed. The effects of ambient dischargers on lightning protectors were investigated. to determine both the discharge behavior and performance. The starting potential of the discharger configuration increased with clearance of tip of the central discharger from surrounding dischargers, instead of increasing with the average spacing between dischargers. The point of strike of lightning discharge depended on the line of least stress rather than the height clearance from the cloud: which determined the charge structure and dynamics of the cloud particulatesItem A case study of the depth of fresh/ Salt water interface using values of freshwater heads in groundwater of variable density(2012) Adegoke, J. A.; Owoeye, O. I.; Ozebo, V. C."Almost two thirds of the world's population lives within 400 km of the ocean shoreline; just over half live within 200 km, an area only taking up 10% of the earth's surface. As the world's population continues to grow at an alarming rate, fresh water supplies are constantly being depleted, bringing with it issues such as saltwater intrusion and increasing the importance of groundwater monitoring, management, and conservation. Constant monitoring of the fresh/salt water interface is necessary for proper management of ground water resources. This work studies the variation in the depth of fresh/salt water interface using different values of freshwater heads extracted from heads in coastal groundwater system near The Hague, Netherlands along sections P-DD. Results showed that high density difference between freshwater and saltwater has little effect on the depth of fresh/saltwater interface."Item Characteristics of total solar radiation in an urban tropical environment(2012) Adeniyi M. O.,; Nymphas E. F.; Oladiran, E. O.The maximum total solar radiation in Ibadan (7.38° N, 3.93° E), Nigeria occurred around 13 and 14h local time (LT) and it varied from an average value of 584.3±10.9 Wm-2 in the wet season (April to October) to 642.5±10.8 Wm-2 in the dry season (November to March) throughout the period of 1997 to 2001. Maximum total solar radiation had two peaks, one in March/April/May with value 750.3±41 Wm-2 and the other in October/November with value 633.1±63.5 Wm-2. The minimum was in July/August with the value 404.8±54 Wm-2. Diurnal total solar radiation had a similar variation with mean day total solar radiation; the latter had its maxima and minimum values to be 564.7±19, 488±36 and 308.4±40 respectively. The annual trend of solar radiation was positive throughout the period considered, which revealed global brightening. The values of total solar radiation observed in Ibadan compared well with those obtained at Ife (7.55° N, 4.56° E) a nearby tropical station. A time lag of about 3 h between the peak of the diurnal temperature and solar radiation was observed. During the month of July or August as the case may be, there was little or no time lag between the time of maximum total solar radiation and maximum diurnal temperature. Significant intra-annual solar radiation cycles (at 0.05 significant level) of 360 to 370 days (1 per year); 180 to 200 days (2 per year), 90 to 121 days (3 per year), 45 to 70days (5 per year); 20 to 35 days (10 per year), 4 to 16 days (20 per year) were obtained for all the years (1997 to 2001).Item Characteristics of worst hour rainfall rate for radio wave propagation modelling in Nigeria(springer, 2019) Osita I.; Nymphas E.F.Radio waves especially at the millimeter-wave band are known to be attenuated by rain. Radio engineers and designers need to be able to predict the time of the day when radio signal will be attenuated so as to provide measures to mitigate this effect. This is achieved by characterizing the rainfall intensity for a particular region of interest into worst month and worst hour of the day. This paper characterized rainfall in Nigeria into worst year, worst month, and worst hour. It is shown that for the period of study, 2008 and 2009 are the worst years, while September is the most frequent worst month in most of the stations. The evening time (LT) is the worst hours of the day in virtually all the stations.Item Characterization of tropical rainfall structure for some selected locations in Nigeria(2021) Osita, I.; Nymphas,E.F.Rainfall rate for any location is required for rain attenuation modeling for the region of interest. The characteristics of tropical rainfall structure in Nigeria have been investigated. The data was collected from the Tropical Data Acquisition network (TRODAN) set up by the Center for Atmospheric Research (CAR) in Nigeria. The rainfall rates were measured at 5-minutes integration time. The results were then compared with those predicted by the ITU-R model, and those from other tropical locations. The results revealed that the ITU-R model performs best only in the Southern Guinea Savannah (SGS) region of the country. In other geographical locations, the ITU-R model either under-estimates or over-estimates rainfall rates. The Cumulative Distribution Functions (CDFs) at the 0.01% time of exceedence showed that the percentage difference in the measured rain rate and the ITU-R estimates varied from a minimum of 4.89% in SGS to a maximum of 22.93% in the Derived Savannah (DS). At the 0.001% of time, these differences varied from a minimum of 11.90% to a maximum of 38.80% in these respective regions. These results and others from the tropics suggest the need for the modification of the ITU-R model for predicting rain attenuation in the tropical region to take into account the peculiar characteristics of rainfall in the region.Item Characterizing buried metallic objects in porous media from attenuation fluctuations(Academic Journals Inc, 2013) Akinyemi, O. D.; Adegoke, J. A.; Salam, M. A.; Badmus, B. S.; Awokola, S. O."Study of attenuation characteristics of electromagnetic signals passing through porous media is becoming increasing relevant in providing important insights into the physical properties of the medium and objects that are buried therein. Laboratory experiments have been carried out in this work to determine the relationship between Q-factor of the electromagnetic signal passing through buried metals and the porosity of the surrounding sediments. Sediments were obtained from Erinle River in Ilobu, Southwestern Nigeria and Iron, Silver and Copper plates of similar dimensions were buried inside box-filled sediment in succession. Electromagnetic signal was passed through metal, sediments and sediments with buried metals while lissajous figures generated at different frequencies were analyzed to assess the impacts of buried objects. Results showed that Q-factor decreased as the porosity of riverbed sediments increased. Of the metals buried inside the sediments, Iron had the most attenuation effect while Silver plates had the least, except at frequency 400Hz where Copper had the least and at 600Hz where there were some overlaps between Silver and Copper. Q-factor increased, for all metals and at all signals frequencies, up to a maximum value at the porosity of 0.24 and thereafter decreased. Knowledge of Q- factor from attenuated signals is therefore, a useful way to characterize and identify buried materials "Item Comparison analyses of different models used to determine soil thermal conductivity and diffusivity at nimex site, Ibadan(2021) Nwaokoro,E.; Nymphas,E.F.Soil thermal properties regulate the separation of energy fluxes at the ground surface and they control the exchange of energy and mass between the soil and the atmosphere. The knowledge of these properties is needed in order to ascertain the heat flux distribution in the soil under steady and non-steady conditions. In this study, which lasted for 11 months starting from March 2006 to January 2007, we estimated soil thermal conductivity and thermal diffusivity at Nigeria Mesoscale Experiment (NIMEX) site, Ibadan using Johansen and Kersten models and Horton Numerical method. The aim of this work is to compare the results obtained from these models and to ascertain the level of agreement of the results. The result showed that for Johansen and Kersten models, the highest mean values of thermal conductivity and thermal diffusivity were obtained in the month of September 2006. For Johansen model the values are 4.18±0.08 Wm-1K-1 and 4.56±5.57*10-8m2s-1 for thermal conductivity and thermal diffusivity respectively and for Kersten model the thermal conductivity and thermal diffusivity values are 1.00±0.05 Wm-1K-1 and 1.07±0.22*10-8 m2s-1 respectively. This may be due to the observed increase in the soil moisture content within this month. The result obtained using Horton Numerical method showed that the highest mean thermal conductivity and thermal diffusivity values of 9.76 ±3.00 Wm-1K-1 and 10.70±3.30*10-8m2s-1 respectively were obtained in the month of December 2006 while the lowest mean values of -0.44 ±14.68 Wm-1K-1 for thermal conductivity and 0.10±12.70*10-8m2s-1 for thermal diffusivity were obtained in the month of September contrary to the results obtained with the first two models. The negative mean thermal conductivity value of -0.44 ±14.68 Wm-1K-1 obtained in the month of September 2006 using Horton Numerical method was probably due to the increase in soil moisture content which is as a result of increase in the amount of rainfall within this month that lowered the temperature at the near soil surfaces. Kersten model is in agreement with Johansen model but has low values making it unsuitable for very low soil moisture. Johansen model is likely the best model for estimating thermal conductivity and diffusivity.Item A computation of laminar flow in open channels and its application to sheet erosion(Devon Science Company, 2011) Adegoke, J. A.; Egbeyale, G. B.Item The concerntration of heavy metals in selected clay samples in ekiti state, southwestern Nigeria(2011) Adegoke, J. A.; Oseni, S. O.; Adegbola, R. B."The presence and possible effect of heavy metal (such as cadmium, zinc, lead, e.t.c) concentration in the clay used in pot making were investigated. Clay samples were collected at three locations where they are used mostly in making pots and other kitchen utensils. The concentrations of heavy metals were determined using the Atomic Absorption Spectrometer (AAS). Results indicate that the concentration Cu, Zn, Cr, Pb, As, and Mn falls within the range of the maximum admissible concentration of heavy metals of several countries mostly in Europe. However, the concentration Cadmium and Nickel are relatively higher than the maximum admissible concentration of toxic metals in soil for countries like Denmark and Sweden."Item 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. "