Joshua Olusegun Okeniyi

Implementation of Kolmogorov–Smirnov P-value computation in Visual Basic®: implication for Microsoft Excel® library function

This paper investigates methodologies for evaluating the probabilistic value (P-value) of the Kolmogorov–Smirnov (K–S) goodness-of-fit test using algorithmic program development implemented in Microsoft® Visual Basic® (VB). Six methods were examined for the one-sided one-sample and two methods for the two-sided one-sample cumulative sampling distributions in the investigative software implementation that was based on machine-precision arithmetic. For sample sizes n≤2000 considered, results from the Smirnov iterative method found optimal accuracy for K–S P-values≥0.02, while those from the SmirnovD were more accurate for lower P-values for the one-sided one-sample distribution statistics. Also, the Durbin matrix method sustained better P-value results than the Durbin recursion method for the two-sided one-sample tests up to n≤700 sample sizes. Based on these results, an algorithm for Microsoft Excel® function was proposed from which a model function was developed and its implementation was used to test the performance of engineering students in a general engineering course across seven departments.

Effect of ethylenediaminetetraacetic disodium dihydrate and sodium nitrite admixtures on steel-rebar corrosion in concrete

This study investigates effect of different concentrations of ethylenediaminetetraacetic disodium dihydrate (EDTA-Na2: C10H14N2Na2O8.2H2O) and sodium nitrite (NaNO2) admixtures, individually or in synergistic/partial NaNO2 replacement model, on the corrosion of concrete steel-rebar in NaCl and in H2SO4 media. Electrochemical monitoring techniques were employed for 48 steel-reinforced concrete samples immersed in the saline/marine and microbial/industrial simulating test environments for 96 days. These test data were subjected to the analyses of the Normal and the Weibull distribution fitting models, for each of which goodness of their fitting the electrochemical test data were studied using the Kolmogorov–Smirnov test statistics. Analysed results showed that EDTA-Na2 admixture concentrations exhibited better inhibition effectiveness, with relatively good effectiveness in their synergistic admixtures, than their equal-mass NaNO2 counterparts in both corrosive environments. Also, post-electrochemical experiment subjection of the concrete samples to testing and analyses of ASTM C39/C39M-03 and ASTM C267-01 showed that use of the optimally inhibiting 8 g EDTA-Na2 (per 2 × 10–3 m3 concrete) culminates in gross reduction in compressive strength of concretes in both test-media. However, lowered EDTA-Na2 concentrations exhibited better strength improvements with high corrosion inhibition in the test environments. These suggest suitability of EDTA-Na2 as an environmental-friendly NaNO2 alternative for inhibiting steel-rebar corrosion in saline/marine and microbial/industrial environments.

Wind profile characteristics and turbine performance analysis in Kano, north-western Nigeria

This study analyzed the electricity generation potential from wind at Kano, Nigeria (12.05°N; 08.2°E; altitude 472.5 m; air density 1.1705 kg/m3). Twenty one years (1987 to 2007) monthly mean wind speed data at a height of 10 m were assessed from the Nigeria Meteorological Department, Oshodi. The data were subjected to different statistical tests and also compared with the two-parameter Weibull probability density function. The outcome shows that the average monthly wind speed ranged from 6.6 to 9.5 m/s. Seasonally, average wind speeds ranged between 6.6 to 8.5 m/s and 7.4 to 9.5 m/s for dry (October to March) and wet (April to September) seasons, respectively. Also, estimated monthly wind power ranged between 3.6 and 12.5 MWh/m2. The most probable and maximum energy carrying wind speeds were also determined and the two parameters of the Weibull statistics were found to lie between 2.1 ≤ k ≤ 4.9 and 7.3 ≤ c ≤ 10.7, respectively. These results indicate that wind speeds at Kano may be economically viable for wind-to-electricity at and above the height of 10 m. In addition, five practical turbine models were assessed for the site’s wind profile, with results suggesting strong economic viability.

Effect of NaNO2 and C6H15NO3 Synergistic Admixtures on Steel-Rebar Corrosion in Concrete Immersed in Aggressive Environments

This paper studies effect of different combinations of NaNO2 (sodium nitrite) and C6H15NO3 (triethanolamine (TEA)), as synergistic admixtures in concrete immersed in NaCl and in H2SO4 test environments, on the corrosion of the concrete reinforcing steel (rebar). Although statistically analysed electrochemical test results confirmed NaNO2 effectiveness, synergistic combinations of 4 g NaNO2

Wind characteristics and energy potential assessment in Akure, South West Nigeria: econometrics and policy implications

This paper analysed 11 years of daily mean wind-speed data, measured at Akure, Ondo State, Nigeria, using Weibull and Rayleigh distribution functions. While both distributions showed good agreements in extreme-value estimation patterns, investigation of their wind-speed characteristics modelling criteria, using goodness-of-fit statistics, revealed that the wind data followed the Weibull more than Rayleigh. Monthly wind-speed of Akure city ranged from 1.41 to 4.24 m/s by the Weibull fittings and from 1.40 to 4.16 m/s by the Rayleigh fittings. Overall results, of 2.71 m/s (Weibull) or 2.70 m/s (Rayleigh) mean wind-speed and 18.51 W/m2 (Weibull) or 22.26 W/m2 (Rayleigh) mean power density, indicated Akure a low wind-speed site, requiring low wind-speed turbine for generating wind energy. Econometric analyses of power output simulations using such turbine system resulted in affordable wind energy cost. These bear policy implications for sustainable wind energy usage in this and similar regions of the world.

Inhibition of Steel-Rebar Corrosion in Industrial/Microbial Simulating-Environment by Morinda lucida

This paper studies inhibition of steel-rebar corrosion in concrete immersed in 0.5 M H2SO4, simulating industrial/microbial environment by the leaf extract of Morinda lucida. Electrochemical monitoring methods were employed for testing different concentrations of the leaf extract admixed in duplicated specimens of steel-reinforced concrete slabs immersed in the acidic test-system. Statistical analyses as per ASTM G16-95 R04 of the experimental results showed that effectiveness of Morinda lucida at inhibiting concrete steel-rebar corrosion increased with the concentration of the admixture. 0.4167% Morinda lucida, per weight of cement, was identified with optimum inhibition efficiency η = 98.78±0.34% followed in effectiveness by 0.3333% Morinda lucida with η = 93.20±1.76% at inhibiting steel-rebar corrosion in the corrosive test-environment.

C10H18N2Na2O10 inhibition and adsorption mechanism on concrete steel-reinforcement corrosion in corrosive environments

Abstract C10H18N2Na2O10 (ethylenediaminetetra-acetic acid disodium salt) inhibition and adsorption mechanism on the corrosion of steel-reinforcement corrosion in concrete immersed in corrosive environments were investigated in this paper. For this, seven different concentrations ranging from 0% to 0.667% C10H18N2Na2O10 per weight of cement were admixed in steel-reinforced concretes immersed in saline and in acidic sulphate test-media and these were monitored using electrochemical techniques. Statistical analyses of the scatter of measured data from these, as per ASTM G16-95 R04, showed that C10H18N2Na2O10 > 0% admixtures portrayed excellent efficiency at inhibiting steel-reinforcement corrosion in the saline environment. However, attaining comparably high inhibition of steel-reinforcement corrosion in concrete immersed in the acidic sulphate environment exhibited greater dependency on high C10H18N2Na2O10 admixture concentration in the steel-reinforced concretes. Different models of adsorption isotherms bear indications of chemical adsorption, chemisorptions, as the prevalent adsorption mechanism of C10H18N2Na2O10 on steel-reinforcement in both of the corrosive environments.

Assessments of Wind-Energy Potential in Selected Sites from Three Geopolitical Zones in Nigeria: Implications for Renewable/Sustainable Rural Electrification

Electricity generation in rural communities is an acute problem militating against socioeconomic well-being of the populace in these communities in developing countries, including Nigeria. In this paper, assessments of wind-energy potential in selected sites from three major geopolitical zones of Nigeria were investigated. For this, daily wind-speed data from Katsina in northern, Warri in southwestern and Calabar in southeastern Nigeria were analysed using the Gumbel and the Weibull probability distributions for assessing wind-energy potential as a renewable/sustainable solution for the countrys rural-electrification problems. Results showed that the wind-speed models identified Katsina with higher wind-speed class than both Warri and Calabar that were otherwise identified as low wind-speed sites. However, econometrics of electricity power simulation at different hub heights of low wind-speed turbine systems showed that the cost of electric-power generation in the three study sites was converging to affordable cost per kWh of electric energy from the wind resource at each site. These power simulations identified cost/kWh of electricity generation at Kaduna as €0.0507, at Warri as €0.0774, and at Calabar as €0.0819. These bare positive implications on renewable/sustainable rural electrification in the study sites even as requisite options for promoting utilization of this viable wind-resource energy in the remote communities in the environs of the study sites were suggested.

Biochemical Characterisation of the Leaf of Morinda Lucida : Prospects for Environmentally-Friendly Steel-Rebar Corrosion-Protection in Aggressive Medium

This paper employs atomic absorption spectroscopy (AAS), Fourier transform infrared spectroscopy (FTIR) and phytochemical screening methods for biochemical characterisation of the inorganic and organic constituents of the leaf of Morinda lucida. AAS results showed that this well-known medicinal-plant is high in iron (Fe = 5143.54 µg/g), low in cadmium (Cd = 2.9506 µg/g) and does not contain chromium (Cr). Also, Euclidean hit-list from the FT-IR instrument suggests Morinda lucida leaf-extract contains S-, N-, Br- and O- containing heteroatoms. The phytochemical analyses indicated presence of tannins, phlobatannins, saponins, flavonoids and terpenoids. These results bare prospects on suitability of leaf-extract from Morinda lucida for environmentally-friendly steel-rebar corrosion-protection in aggressive medium. Preliminary tests based on this showed that use of 0.083 wt% cement of Morinda lucida retarded steel-rebar total-corrosion and eventually reduced corrosion rate as admixture in duplicated 3.5% NaCl-immersed concretes, relative to control samples in the same medium.

Anticorrosion performance ofAnthocleista djalonensison steel-reinforced concrete in a sulphuric-acid medium

ABSTRACT This paper employs electrochemical monitoring methods for studying the anticorrosion performance of the leaf-extract admixture of Anthocleista djalonensis (A. djalonensis) on steel-reinforced concrete immersed in the aggressive medium of a sulphuric-acid (H2SO4) test solution. The electrochemical monitoring methods employed include corrosion potential, corrosion current and corrosion rate. These were used for testing the corrosion responses of specimens of duplicated steel-reinforced concretes in the industrial/microbial simulating test environment. Analyses of these test measurements, as per American Society for Testing and Materials (ASTM) G16-95 R04, shows that the corrosion rate correlates directly with the leaf-extract admixture concentration and inverse functions of noise resistance; the ratio of the standard deviation of the corrosion potential to that of the corrosion current. It is concluded that 0.4167% A. djalonensis (per weight of cement) is the optimum modelling efficiency, from the ranked predictions of the correlation fitting model, by having an inhibition efficiency of η = 96.11 ± 1.14% (predicted) or 89.84 ± 2.46% (experimental) in the medium. Fittings of the predicted and experimental data show that they both follow the Frumkin adsorption isotherm model with a coefficient of determination r2 = 96.17% (predicted) and r2 = 89.88% (experimental). The results of the experimental and predicted model agree in support of using A. djalonensis as an eco-friendly inhibitor of corrosion in the reinforcing steel in concrete designed for the industrial/microbial service environment.