FACULTY OF SCIENCE
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Item Fractional integration and structural breaks in bank share prices in Nigeria(Elsevier, 2015) Gil-Alana, L. A.; Yaya, O.S.; Adepoju, A. A.The paper employs both fractional integration and structural break techniques in studying the daily share prices structure of the banking sector in Nigeria. Our data span between 2001 and 2012, covers periods before and after the global financial crisis. The results obtained using both parametric and semi parametric methods indicate little evidence of mean reversion since most of the orders of integration are equal to or higher than1. Long memory is found in the absolute and squared return series. The possibility of structural breaks is also taken into account and the results show a different number of breaks depending on the bank examined. In general, an increase in the degree of dependence across time is noticed, and the most common break took place in December 2008, probably being related with the world financial crisis affecting also the banking system in NigeriaItem Guinea worm disease and its persistence in some rural communities in Nigeria(2007) Morenikeji, O. A.; Alade, A. O.; Odaibo, A. B.Studies were carried out in six villages of Ogun State, Nigeria from January to December 2004 to identify the reasons for the persistence of guinea worm disease in spite of eradication measures. Pre-tested structured questionnaires were administered to 250 head of households in the endemic villages to assess their knowledge attitude and practice (KAP) in the management of guinea worm disease. The overall prevalence of infection for the study-period was 1.0%. 96.0% of the respondents depended solely on ponds for drinking water during the dry season. 80.0% of the respondents had been infected before 68.0% think that the disease is caused by spiritual attack, while 4.0% associated the disease to drinking bad water. 77.5% did not know if it is possible to prevent the disease. It was observed that immigrant farm labourers and apathy on the part of eradication officials may play vital roles in the transmission of the disease in the area. This study shows that there is need to ascertain and specifically address reasons for the persistence of the disease in areas still endemic.Item Use of block inversion in the 2-D interpretation of apparent resistivity data and its comparison with smooth inversion(Elsevier, 2000) Olayinka, I. A.; Yaramanci, U.The ability of a block inversion scheme, in which polygons are employed to define layers and/or bodies of equal resistivity, in determining the geometry and true resistivity of subsurface structures has been investigated and a simple strategy for deriving the starting model is proposed. A comparison has also been made between block inversion and smooth inversion, the latter being a cell-based scheme. The study entailed the calculation (by forward modelling) of the synthetic data over 2-D geologic models and inversion of the data. The 2-D structures modelled include vertical fault, graben and horst. The Wenner array was used. The results show that the images obtained from smooth inversion are very useful in determining the geometry; however, they can only provide guides to the true resistivity because of the smearing effects. It is shown that the starting model for block inversion can be based on a plane layer earth model. In the presence of sharp, rather than gradational, resistivity discontinuities, the model from block inversion more adequately represents the true subsurface geology, in terms of both the geometry and the formation resistivity. Field examples from a crystalline basement area of Nigeria are presented to demonstrate the versatility of the two resistivity inversion schemes.Item Comparative analysis of rainfall prediction using statistical neural network and classical linear regression model(Medwell Journals, 2011) Udomboso, C. G.; Amahia., G. N.Different types of models have been used in modeling rainfall. Since 1990s however, interest has shifted from traditional models to ANN in rainfall modeling. Many researchers found out that the ANN performed better than such traditional models. In this study, we compared a traditional linear model and ANN in the modeling of rainfall in Ibadan, Nigeria. Ibadan is a city in West Africa, located in the tropical rainforest zone, using the data obtained from the Nigeria Meteorological (NIMET) station. Three variables were considered in this study rainfall, temperature and humidity. In selecting between the two models, we concentrated on the choice of adjusted R2 (R-2 ), Akaike Information Criterion (AIC) and Schwarz Information Criterion (SIC). Though, the MSE and R2 were also used, it was concluded from results that MSE is not a good choice for model selection. This is due to the nature of the rainfall data (which has wide variations). It was found that the Statistical Neural Network (SNN), generally performed better than the traditional (OLS).Item Alternative goodness-of-fit test in logistic regression models(Medwell Journals, 2011) Nja, M. E.; Enang, E. I.; Chukwu, A. U.; Udomboso, C. G.The Deviance and the Pearson chi-square are two traditional goodness-of-fit tests in generalized linear models for which the logistic model is a special case. The effort involved in the computation of either the Deviance or Pearson chi-square statistic is enormous and this provides a reason for prospecting an alternative goodness-of-fit test in logistic regression models with discrete predictor variables. The Deviance is based on the log likelihood function while the Pearson chi-square derives from the discrepancies between observed and predicted counts. Replacing observed and predicted counts with observed proportions and predicted probabilities, respectively in a cross-classification data arrangement, the standard error of estimate is proposed as an alternative goodness-of-fit test in logistic regression models. The illustrative example returns favourable comparisons with Deviance and the Pearson chi-square statistics.Item Hydraulic, textural and geochemical characteristics of the Ajali Formation, Anambra Basin, Nigeria: implication for groundwater quality(Department of Geology, 2009) Tijani, M N.; Nton, M. N."This study highlights the distribution of hydraulic conductivity (K) in the regional aquiferous Ajali Formation of SE-Nigeria on one hand and assesses the possible influences of textural and geochemical characteristics on the hydraulic conductivity on the other hand. The investigation approach involved field sampling and collection of 12 sandstone samples from different outcrop locations, followed by laboratory studies such as grain-size analysis (GSA), constant head permeameter test and geochemical analysis of major and trace elements using X-ray fluorescence method. GSA and textural studies show that the sandstones range from fine to medium sands, constituting about \75–99% sand fraction, with graphic mean grain size of 0.23–0.53 mm. Other parameters such as coefficient of uniformity (Cu) range from 1.58 to 5.25 (av. 2.75), while standard deviation (sorting) values of 0.56Ø– 1.24Ø imply moderately well sorted materials. In addition, the order of the estimated K values is Kpermeameter>KBeyer>KHazen>KKozeny-Carmen>KFair-Hatch with average values of 1.4˟10-3, 4.4˟10-4, 3.8˟10-4, 2.2˟10-4 and 8.1˟10-5 m/s, respectively. These values fall within the range of 10-5 and 10-3 m/s for fine to medium sands. However, multivariate factor analysis of the data revealed significant positive dependence of the empirically determined K values on graphic mean grain size and percentage sand content and much less dependence on sorting and total porosity. Geochemical profiles of the fresh samples are dominated by quartz with corresponding SiO2 content of 76.1–98.2% (av. 89.7%) while other major oxides are generally below 1.0 wt.% in the fresh samples. However, the ferruginized samples exhibited elevated concentrations of Al2O3 (3.50–11.60 wt.%) and Fe2O3 (1.80–3.60 wt.%), which are clear indications of weathering/ferruginization processes with attendant trace metal release/enrichment (2.5 mg/l Cu, 7.5 mg/l Pb, 6.5 mg/l Zn, 3.9 mg/l Ni and 19.6 mg/l Cr) call for concern in respect of the chemical quality of the groundwater system. The associated groundwater is generally soft, slightly acidic, and with low dissolved solids (EC = 14–134 ls/cm) dominated by silica; implying water from clean sandy aquifer devoid of labile and weatherable minerals. Nonetheless, most of the metals (with exception of Si, Fe and Mn) exhibited higher degree of mobility (2–12 folds), which can be attributed to reduction of Fe-/Mn-oxyhydroxides as sinks/hosts for trace metals. Consequently, infiltration-induced geochemical reactions (redox, ferruginization and leaching processes) signify potential environmental impact in terms of groundwater quality as well as borehole/aquifer management, especially under humid tropical environment of the study area. "