Abstract: In many developing countries wood is the main energy source, and its exploitation is accelerating deforestation and desertification. In order to reduce wood consumption, an innovative biomass press was designed, aimed at providing alternative fuel by compacting dry waste biomass. The machine is based only on mechanisms, and can work by animal power, in order that it can be used in places where there is not electric power. The main machine element is a cam, designed according to the criterion of making manual running possible, on the basis of an experimental biomass behaviour law. The whole machine design was conceived with the aim of allowing construction in the developing countries. A prototype for research was realised, equipped with an electric motor and electronic control system. Biomass compaction tests were carried out, from which the machine characteristics were derived, and the validity of the biomass behaviour model was confirmed. Pilot plants, both manual and electric, were realised in Burundi and Chad, obtaining encouraging results as far as the appropriateness of this technology to developing countries is concerned.
Abstract: In this paper, Monte Carlo method (MCM) is used to analyze the uncertainty of optical calibration of end standards using both contact and non-contact techniques to validate the uncertainty values obtained by the conventional method, Guide to the expression of Uncertainty in Measurement (GUM). Number of trials (M=104) is simulated with the probability density function (pdf) for each quantity, and the comparison between the results of the MCM and the GUM shows good agreement which in turn validates the uncertainty values obtained by the conventional method. The statistical analysis, variables' distributions, and the output of each technique are discussed in detail.
Abstract: The NST 37-2 steel represents about 75% volume of Nigerian-produced steel which is yet to be fully characterized for its fatigue behavior. Thus, its suitability for many applications is questionable. This paper presents a framework based on the theory of elasto-plasticity in order to make appropriate recommendations in this regard. Experimentally, tensile tests were carried out on test specimens to establish the baseline material properties of the steel in annealed, as-rolled, normalized and hardened/tempered conditions. Fatigue tests were then conducted at 60% Su; 70% Su and 80% Su of the test material and fractographic examinations on the test specimens were subsequently carried out. The frequency harmonic fatigue analysis was implemented in the ANSYS software environment for the numerical study. The elastic-plastic material property was described by the von Mises yield criterion, the flow rule of Prandtl-Reuss, and the kinematic hardening rule of Prager. The numerical results indicate with respect to rate-dependence fatigue behavior that the annealed test specimen is most resilient under cyclic deformation as compared with the normalized, hardened/tempered and as-rolled specimens respectively. The experimental and numerical results were found to be in close agreement and based on the general performance, the steel material is recommended for use in low cycle, quasi-static fatigue applications.
Abstract: Study was carried out to develop a composite material from agro waste consisting of sawdust and palm kernel shell and to determine its physical and mechanical properties. The sawdust / palm kernel shell compositions by weight were in the ratios of 100: 0, 90: 10, 80: 20, 70: 30, 60: 40 and 50:50. Urea formaldehyde was used as the test binder at concentrations of 20% of oven dry weight of agro waste. Particle size of agro waste used was 300µm .Yield strength, ultimate tensile strength, modulus of elasticity, modulus of rupture, internal bond strength, density, thickness swelling and water absorption of the formed composite materials were determined and observed to be enhanced at high palm kernel shell composition. The composite composition by weight that gave the best results out of the six compositions tested was the one with sawdust: palm kernel composition of 50%:50% with its properties as: yield strength ( 4.47 N/mm2) ,ultimate tensile strength (7.75 N/mm2), modulus of elasticity (2603 N/mm2), modulus of rupture (16.67 N/mm2 ), internal bond strength ( 0.54 N/mm2 ), thickness swelling (10.30%) ,water absorption (18.90%) and density (996.18kg/m3).
Abstract: The photovoltaic (pv) forced convection solar dryer comprises the solar collector, dryer and pv assemblies. It is designed for a continuous operation throughout the day. The direct solar irradiation is utilized during sunshine hours and it automatically switches power supply to the battery during cloud covers and non-insolation periods. The inclusion of a heat reservoir enables heat transfer to continue during this period. In this study, thermal and dryer analyses were done. Experimental investigations were carried out to evaluate the performance of the system by drying plantain chips. The useful power collected was found to be, 391.50W, collector efficiency, 65.6%, dryer efficiency, 39.6%, average drying rate during insolation, 0.0169kg/hr and total drying time was 23 hours. The maximum temperature attained was 55oC. The average drying non insolation period was 0.0112kg/hr. The capital cost is less than $350.
Abstract: The most important factors that influence biodiesel production are temperature, molar ratio, catalyst amount, time and degree of agitation. This study investigated the effects of temperature, molar ratio and degree of agitation and their interactions on the yield and purity of biodiesel produced from Jatropha oil. Factorial design and response surface methodology (RSM) were used to predict yield and purity of biodiesel as functions of the three variables. Interactions of all the factors were found to be significant on both yield and purity responses. Temperature and molar ratio main effects were found to be significant on the yield whereas only temperature main effect was significant on the purity of the biodiesel. The optimum conditions of operations were; temperature of 54 oC, molar ratio of methanol to oil of 6:1 and stirring speed of 660 rpm. Using these conditions, biodiesel yield of 95% (wt) was obtained with a purity of 97%. This model can be used to predict the yield and purity of biodiesel from jatropha oil within the ranges of temperature (30 – 60oC), stirring rate (300 -900 rpm), and molar ratio (3 – 9 mol/mol) studied.
Abstract: The thermochemical properties of varieties of species needed to assess the most prominent pathways of tropospheric ozone transformation have been established. In the troposphere, ozone which is a secondary pollution produced by photochemical induced transformation, acts as an oxidizing agent to numerous atmospheric reactions leading to the formation of particulate matter. Based on the climate related problems resulting from the precursor of particulate matter, it is adequate to establish the feasible routes of ozone formation. In this study, the electronic structure methods which approximate the Schrödinger equation to compute Gibbs free energies and enthalpies of formation of the various chemical species participating in the reactions were used. These thermodynamic properties were determined using four computational model chemistry methods integrated in the Gaussian 03 (G03) chemistry package. Five known reaction pathways for the formation of NO2 (the O3 precursor specie), as well as the dominant ozone formation route from NO2 were examined and their energies determined. Of all the computational methods, the complete basis set (CBS-4M) method produced energies for all species of the five reaction routes. Out of the five routes, only the reactions involving radical species were favoured to completion over a temperature range of -100 and +100oC. The most relevant reaction route for the formation of NO2 and subsequently O3 is that involving the peroxyl acetyl nitrate (PAN) and hydroxyl radicals. Chemical equilibrium analyses of the reaction routes also indicated that reduction in temperature encourages NO2 formation while increase in temperature favours O3 production.
Abstract: Lateritic soils are pedogenic surface deposits which occur in vast areas of tropical and subtropical regions of the world and find use as construction material in diverse civil engineering aspects. But, the predominance of kaolinitic 1:1 lattice clay mineral and coating of the clayey constituents with sesquioxides limits the ability of the soil from achieving very low hydraulic conductivity, (k) required for some geotechnical/geoenvironmental structures. The present study investigates the influence of low percent bentonite on the hydraulic conductivity of a residually derived lateritic soil. Accordingly, the test programme involved specimens of lateritic soil - bentonite mixtures containing 0, 2.5, 5, 7.5 and 10% bentonite (by dry weight of soil) prepared at different compaction states (optimum, dry and wet of optimum content), compacted with British Standard Heavy, (BSH) compactive effort and permeated in compaction mould permeameter using falling head test method. Results indicate that reductions in hydraulic conductivity values ranged from 1 x 10-9 to 6.79 x 10-11 m/s (i.e. two orders of magnitude) as the percentage of bentonite increased from 0 to 10%. Soil mixtures with up to 5% bentonite content recorded the lowest k values at 2% wet of optimum moisture content, beyond which an increase in k followed. For soil mixtures containing 7.5 and 10% bentonite, a continuous decrease in k was observed. Furthermore, a non – linear relationship between log k and bentonite content was established. These results met or exceeded specification requirements for the aforementioned structures which therefore suggest that the potentials of lateritic soils as a geomaterial for the construction of hydraulic structures can be fully realized when treated with bentonite.
Abstract: In this paper, a 2x2 and a 4x4 indoor MIMO measurement campaign at a (2 -5) GHz is presented. A statistical analysis to study the effects of a 2x2 and a 4x4 MIMO on the channel capacity with their respective received fixed signal to noise ratios were analyzed both in the LOS and in NLOS scenarios. Furthermore, investigations were carried out on all the possible wide band antenna polarizations in order to ascertain which mode of propagation yields a highly decorrelated spatial channel. The three received signal to noise ratios namely 10dB, 20dB and 30dB were used to model various received signal powers. It was found that copolar configurations HH and VV yielded the maximum capacity values both in the LOS and in NLOS respectively. Finally, a validity test was conducted and it was realized that the empirical distribution is similar and within the theoretical (i.i.d) distribution.