Investigating chaos in the Nigerian Asset and Resource Management (ARM) discovery fund

This paper investigates chaos in a Nigerian mutual fund, Asset and Resource Management Company Limited (ARM) for a period of eleven years. The existence of chaotic signals in the data was identified by the reconstruction of the phase space of the daily closing price of the fund and the delay time was quantified using mutual information function and the embedding dimension by the false nearest neighbours, where the values were identified to be 15 and 20 respectively. The presence of chaotic signals in the ARM data was further confirmed by the correlation dimension method which yielded a dimension of 2.2 and by the Lyapunov exponent, in which the largest Lyapunov exponent is 0.0528. The predictability of the fund was evaluated from the inverse of the largest Lyapunov exponent as 19 days

Correlation between fibre length characteristics and mechanical properties of Tectona grandis wood

This study considered the relationship between fibre length characteristics and mechanical properties of Tectona grandis wood aged 15, 20 and 25-year. Six trees of even aged and similar class diameter were used for the study. Wood samples used for the study were systematically collected from three portions at 10, 50 and 90% of the tree height. The test samples were prepared along the radial positions from the pith to the bark. The relationship between fibre length and mechanical properties were examined using linear regression models and correlation coefficient. The results obtained from the correlation analysis carried out to examine the linear relationship between fibre length and mechanical properties of T. grandis wood were 0.924, 0.929 and 0.940 for MOR, MOE and CS parallel to grain. The relationship was highly significant (p < 0.05). Also the correlation coefficient (r) between fibre length and mechanical properties of T. grandis wood were highly significant (p < 0.001). Therefore, fibre length characteristics can be used as an index in predicting the mechanical properties of T. grandis wood

Characterization of selected Nigerian biomass for combustion and pyrolysis applications

Biomass is the most utilized form of renewable energy, especially in developing nations, and is a possible replacement for fossil fuel in power generation. The most commonly used method for recovering energy from biomass is combustion. Many countries are exploring the utilization of energy crops and indigenous residues to deliver sustainable sources of biomass. For these bio-resources, detailed characterization of the fuel properties is essential in order to optimize the combustion processes. In this study, some potential energy crops and woods from Nigeria, namely Terminalia superba, Gmelina arborea, Lophira alata, Nauclea diderrichii, and also one abundant agricultural residue, palm kernel expellers (PKE), were characterized for their combustion properties. Standard characterization methods such as proximate and ultimate analyses, metals analysis, and ash fusion test were used for this purpose and the results were compared with some U.K. biomass. In addition, their thermal conversion was assessed by thermogravimetric analysis and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). Finally, combustion studies were conducted by suspending single biomass particles in a methane flame to obtain information on reactivities and combustion characteristics. Results indicate that the ash fractions in the Nigerian woods were low in K, Si, and Ca, resulting in low calculated alkali indices, hence these fuels are not predicted to cause severe fouling problems. Furthermore, the analysis of the evolved product during devolatilisation from Py-GC-MS suggests that the content of oil is high in Gmelina. Finally, the results from the single particle combustion experiments revealed a longer char burn out rate for Lophira and Nauclea when compared with those of Terminalia and Gmelina

Efficacy of commonly used wood preservatives against subterranean termites in Akungba-Akoko, Ondo State, Nigeria

The efficacy of three commonly used wood preservatives in Akungba-Akoko, against subterranean termites attack was investigated using three  lesser durable wood species. Samples were prepared according to ASTM D3345-17 for durability test. All samples were oven dried for 24 hours at  103±2 oC prior to preservative treatments. Treated wood samples were buried half way in the soil and exposed to subterranean termites for 12 weeks at a timber grave yard. Weekly visual rating of the stakes was performed, while a gravimetric weight loss assessment was carried out after the 12 weeks of exposure. Results revealed the presence of two termite species: Macrotermes subhyalinus Rambur and Microtermes spp. within the graveyard. Density of the wood species ranged from 542.28±42.40 Kg/m3 (P. macrocarpa) to 237.99±6.94 Kg/m3 (R. heudelotii). Kinematic viscosities (25 oC) of the liquid preservatives ranged from 1433.25±30.96 cSt (Timbguard™) to 3909.75±225.76 cSt (Solignum). Preservative absorption capacity ranged from 7.82±2.31 % (P. macrocarpa treated with spent engine oil) to 52.16±9.36 % (R. heudelotii treated with Timbguard™), while preservative retention ranged from 2.57±0.17 Kg/m3 (R. heudelotii treated with spent engine oil) to 14.42±1.13 Kg/m3 (A. boonei treated with Timbguard™). All the three preservatives were effective in protecting the three selected wood species with gravimetric weight loss values less than 10 %; establishing their efficacy in protecting wood material against subterranean termites. Keywords: Wood preservatives, subterranean termites, Preservative efficacy, Wood protectio

Tropospheric delay in microwave propagation in Nigeria

Satellite communication systems suffer from the systematic error of tropospheric delay. Accurate estimation of this delay is essential for communication budget and planning. This study investigates the tropospheric delay in three Nigeria cities: Abuja, Lagos, Port-Harcourt using two different models (Saastominen and Hopfield). Three year atmospheric data for surface pressure, relative humidity and temperature obtained at 5-mins interval were acquired from the Tropospheric Data Acquisition Network (TRODAN) archives. Computed radio refractivity values showed distinct seasonal dependence in Abuja with low and high values during the dry and wet season respectively. The Hopfield model predicts higher hydrostatic delay values than the Saastominen model. In the non-hydrostatic delay, the two models converge to a single values at high temperature. Theorems were proposed with proofs to explain the relationship observed between the two models