Ojo J.S.,Federal University of Technology Akurre
Advances in Space Research | Year: 2017
The study of the influence of cloud cover on satellite propagation links is becoming more demanding due to the requirement of larger bandwidth for different satellite applications. Cloud attenuation is one of the major factors to consider for optimum performance of Ka/V and other higher frequency bands. In this paper, the geo-spatial distribution of cloud coverage over some chosen stations in Nigeria has been considered. The substantial scale spatial dispersion of cloud cover based on synoptic meteorological data and the possible impact on satellite communication links at higher frequency bands was also investigated. The investigation was based on 5. years (2008-2012) achieved cloud cover data collected by the Nigerian Meteorological Agency (NIMET) Federal Ministry of Aviation, Oshodi Lagos over four synoptic hours of the day covering day and night. The performances of satellite signals as they traverse through the cloud and cloud noise temperature at different seasons and over different hours of days at Ku/W-bands frequency are also examined. The overall result shows that the additional total atmospheric noise temperature due to the clear air effect and the noise temperature from the cloud reduces the signal-to-noise ratio of the satellite receiver systems, leading to more signal loss and if not adequately taken care of may lead to significant outage. The present results will be useful for Earth-space link budgeting, especially for the proposed multi-sensors communication satellite systems in Nigeria. © 2017 COSPAR.
Akinbinu V.A.,Federal University of Technology Akurre
Engineering Geology | Year: 2017
The aim of this research is to investigate whether a relationship exists or not between various brittleness concepts and fragmentation of rock under brittle compression. The term ‘brittleness’ at present has no clear definition. Fragmentation of rock under compression depends on it self-sustaining failure and the energy available at the peak strength to shatter the rock. It appears from review of the literature that no research has attempted to link rock brittleness and its corresponding fragmentation in compression. Rock failure under conventional compression tests and the subsequent fragments size distribution is a little-understood phenomenon. The research carried out involved determination of post-peak modulus for various rocks using a closed loop servo-controlled testing machine and fragmentation of the rock in brittle compression in accordance to ISRM (2007) suggested methods. Various brittleness concepts were evaluated from static mechanical properties, energy balance, normalised pre-failure curves and extension strain criterion. They were compared with fragments size obtained from compression. Brittleness concepts form static mechanical properties show that the higher its value the finer the fragmentation. Both concepts from normalised pre-failure curves and extension strain criterion appear to treat fragmentation of Class I and Class II rocks as a separate entity. They show better correlation with fragmentation for the segregated samples, Class I and Class II than other concepts. The concepts correlated with the post-peak modulus of the rocks and as such could be useful to quantify the brittleness of the rock under compression. © 2017 Elsevier B.V.
Mogaji K.A.,Federal University of Technology Akurre
Pure and Applied Geophysics | Year: 2017
Producing a bias-free vulnerability assessment map model is significantly needed for planning a scheme of groundwater quality protection. This study developed a GIS-based AHPDST vulnerability index model for producing groundwater vulnerability model map in the hard rock terrain, Nigeria by exploiting the potentials of analytic hierarchy process (AHP) and Dempster–Shafer theory (DST) data mining models. The acquired borehole and geophysical data in the study area were processed to derive five groundwater vulnerability conditioning factors (GVCFs), namely recharge rate, aquifer transmissivity, hydraulic conductivity, transverse resistance and longitudinal conductance. The produced GVCFs’ thematic maps were multi-criterially analyzed by employing the mechanisms of AHP and DST models to determine the normalized weight (W) parameter for the GVCFs and mass function factors (MFFs) parameter for the GVCFs’ thematic maps’ class boundaries, respectively. Based on the application of the weighted linear average technique, the determined W and MFFs parameters were synthesized to develop groundwater vulnerability potential index (GVPI)-based AHPDST model algorithm. The developed model was applied to establish four GVPI mass/belief function indices. The estimates based on the applied GVPI belief function indices were processed in GIS environment to create prospective groundwater vulnerability potential index maps. The most representative of the resulting vulnerability maps (the GVPIBel map) was considered for producing the groundwater vulnerability potential zones (GVPZ) map for the area. The produced GVPZ map established 48 and 52% of the areal extent to be covered by the lows/moderate and highs vulnerable zones, respectively. The success and the prediction rates of the produced GVPZ map were determined using the relative operating characteristics technique to give 82.3 and 77.7%, respectively. The analyzed results reveal that the developed GVPI-based AHPDST model algorithm is capable of producing efficient groundwater vulnerability potential zones prediction map and characterizing the predicted zones uncertainty via the DST mechanism processes in the area. The produced GVPZ map in this study can be used by decision makers to formulate appropriate groundwater management strategies and the approach may be well opted in other hard rock regions of the world, especially in economically poor nations. © 2017, Springer International Publishing.
Olajuyigbe F.M.,Federal University of Technology Akurre
Cellulose | Year: 2017
Saccharification of cellulose is a promising method for production of biofuels. However, low bioconversion efficiency of cellulose to soluble sugars is a major challenge. In this study, a cellulolytic strain of Fusarium oxysporum was cultivated on pure cellulosic substrates (avicel, α-cellulose, carboxymethylcellulose and methylcellulose) and conversion efficiency into glucose was investigated. Production of exo- and endoglucanases during the bioconversion process was evaluated. Influence of pH on saccharification of cellulose and enzyme production by F. oxysporum were determined. Highest yield of glucose (1.76 μmol/ml) was obtained from F. oxysporum on methyl cellulose at 192 h under basal conditions. Liberated glucose under optimized condition of pH 6.0 at 96 h of fermentation was 2.12 μmol/ml with maximum production of exo- and endoglucanases (23.70 and 34.72 U/mg protein, respectively). The crude exo- and endoglucanases had optimum activities at pH 8.0, 70 °C and pH 7.0, 50 °C, respectively. The enzymes were stable over pH of 4.0–7.0 with relative residual activity above 60% after 1 h incubation. Exoglucanase activity was enhanced by Ca2+ and Cu2+ at 5 mM and Mg2+ at 10 mM. Endoglucanase activity was greatly enhanced in the presence of Mn2+, Ca2+, Mg2+, Cu2+ and Fe3+ at 5 and 10 mM. Activities of both enzymes were inhibited in the presence of Hg2+ at 5 and 10 mM. Results show that F. oxysporum possessed good cellulolytic enzyme system for efficient conversion of cellulose. Exhibited thermotolerance of exoglucanase with the striking tolerance of endoglucanase to metal ions demonstrate potentials of enzymes for biofuel industry. © 2017 Springer Science+Business Media B.V.
Oboh G.,Federal University of Technology Akurre
Journal of medicinal food | Year: 2010
The stem of sorghum is used as color additives in cooking meals and taken as beverages when steeped or boiled in water as folklore for the management of anemia and some other diseases. This study sought to assess the antioxidant and neuroprotective potentials of red dye extract from sorghum stem on cyclophosphamide-induced oxidative stress in rat brain. Wistar strain albino rats were fed diet supplemented with the red dye (0.5% and 1.0% inclusion) for 14 days. There was no significant difference (P>.05) in average feed intake and weight gain of rats fed the basal diet and the red dye-supplemented diet. However, intraperitoneal administration of cyclophosphamide (75 mg/kg of body weight) 24 hours prior the termination of the experiment caused a significant (P<.05) increase in the brain malondialdehyde (MDA) content and serum activities of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase in those rats fed diet without the dye supplement, whereas there was a significant decrease (P<.05) in brain MDA content and serum enzyme activities in rats fed diet with the dye in a concentration-dependent manner. The protective effect of the red dye against cyclophosphamide-induced oxidative stress could be attributed to the high phenolic content (56.2%) and antioxidant activities of the red dye as typified by 2,2-diphenyl-1-picrylhydrazyl free radical scavenging ability, reducing properties, and Fe(2+) chelating ability. Therefore, dietary inclusion of the red dye from sorghum stem could be harnessed in the management of neurodegenerative diseases associated with oxidative stress.
Oyetayo O.V.,Federal University of Technology Akurre
African Journal of Traditional, Complementary and Alternative Medicines | Year: 2011
For centuries, mushrooms have been appreciated as sources of food nutrients and pharmacologically important compounds useful in medicine. Yet not all the medicinal properties of mushrooms have been exploited. The above statement is more pertinent to mushrooms that are indigenous to Nigeria. There are inadequate data on the identity and medicinal properties of these wild mushrooms. Information on the ethnomedicinal uses of some mushrooms such as Pleurotus tuber-regium used for headache, stomach pain fever, cold, constipation; Lentinus squarullosus for mumps, heart diseases; Termitomyces microcarpus for gonorrhea; Calvatia cyathiformis for leucorrhea, barreness; Ganoderma lucidum for treating arthritis, neoplasia; G. resinaceum used for hyperglycemia, liver diseases (hepatoprotector); G. applanatum used as antioxidant and for diabetes had been gathered through survey. The above information is mostly obtained from traditional herbalists who in most cases will not disclose their preparation compositions. A lot of these mushrooms are obtained only in the wild. Scientific documents of the identities and medicinal properties are still scanty. Preliminary studies on some species of Temitomyces, Lenzites and Lentinus species showed that they possess appreciable antimicrobial and antioxidant properties. Moreover, molecular characterization also reveals that they are not 100% homologous with existing sequences under the same name in GenBank. It is therefore pertinent that well structured studies on their ecology, identification and medicinal uses be carried out. This will make the full exploitation of the medicinal potentials of mushrooms indigenous to Nigeria realizable.
Aje I.,Federal University of Technology Akurre
Engineering, Construction and Architectural Management | Year: 2012
Purpose - Prequalification of contractors is a very important step in construction project procurement under the contract "Due Process" policy in Nigeria. The purpose of this study, therefore, is to investigate the impact of contractors' prequalification on cost, time and quality performance of construction projects. Design/methodology/approach - Data were collected with the aid of a questionnaire addressed to construction practitioners selected from clients, consultants and contractors' organizations. Also archival data on 77 completed building projects relating to prequalification assessment of contractors and project delivery variables were sourced from consultant quantity surveyors. The data were analysed with the aid of mean score and one-way analysis of variance (ANOVA). Findings - The results show that contractors' prequalification has significant impact on time and quality performance of construction projects as evidenced by p/-values of 0.039 and 0.030, respectively. Practical implications - The findings should provide a valuable reference for clients and consultants during contractors' prequalification and contract award. Originality/value - The outcome of this paper will assist clients and consultants in the construction industry to carry out objective assessment of contractors' potential performance in relation to project goals prior to contract award. © 2012 Emerald Group Publishing Limited. All rights reserved.
Alaneme K.K.,Federal University of Technology Akurre
International Journal of Mechanical and Materials Engineering | Year: 2012
The influence of thermo-mechanical treatment on the percent porosity and mechanical behaviour of SiC reinforced aluminium alloy (6063) composites was investigated. AA 6063 - SiC p composites having 6 and 9 vol. % of SiC were produced by the use of Borax additive and double stir casting process. The composites were cold rolled to 20, 25 and 35% deformation before solution heat-treating at 550°C for 1hour cooling rapidly in water. Density measurements and percent porosity of the composites were evaluated; also their tensile properties and fracture toughness were assessed. The results indicate that the cold rolling and solution heat-treating processes resulted in remarkable reduction in porosity levels in the composites (≤ 1.9% porosity). A good uniform distribution of the SiC particulates in the AA 6063 was also produced. The tensile properties and fracture toughness of the composites improved significantly with the adoption of the cold rolling and solution heat-treatment process.
Alaneme K.K.,Federal University of Technology Akurre
Materials Research | Year: 2011
The fracture behavior of dual phase medium carbon low alloy steels produced using two different chemical compositions (A - 0.34C, 0.75Mn, 0.12Cr, 0.13Ni steel and B - 0.3C, 0.97Mn, 0.15Cr steel) was investigated using circumferential notched tensile (CNT) specimens. Intercritical treatments were performed on samples with composition A by 1) austenitizing at 860 °C for 1 hour cooling in air, then treating at 770 °C for 30 minutes before oil quenching; 2) austenitizing at 860 °C for 1 hour quenching in oil, then treating at 770 °C for 30 minutes before quenching in oil; and 3) austenitizing at 860 °C for 1 hour, super-cooling to 770 °C and then quenching in oil. Samples of composition B were subjected to intercritical treatment at temperatures of 740, 760, and 780 °C for 30 minutes, followed by quenching rapidly in oil. Tensile testing was then performed on specimens without notches and the CNT specimens. It was observed that the dual phase steel produced from procedure (2) yielded a fine distribution of ferrite and martensite which gave the best combination of tensile properties and fracture toughness for composition A while the dual phase structure produced by treating at 760 °C yielded the best combination of tensile properties and fracture toughness for composition B. The fracture toughness results evaluated from the test were found to be valid (in plain strain condition) and a high correlation between the fracture toughness and notch tensile strength was observed. The fracture toughness values were also found to be in close agreement with data available in literature.
Kareem B.,Federal University of Technology Akurre
Case Studies in Engineering Failure Analysis | Year: 2015
In this study, mechanical crankshaft failures for automobiles are evaluated based on experts' opinion. This was done using data obtained using techniques based on oral interviews and questionnaire administration on mechanical failure of crankshafts from the experts working in the areas of automobile maintenance and crankshafts reconditioning. The data collected were analyzed using statistical methods based on probability. With this technique, probability of failure for each category of automobiles namely private, commercial cars and buses were evaluated. The results obtained show that private cars had lowest failure rate at the initial stage while commercial buses had the highest failure rate. At later periods all categories of automobile crankshafts considered had their failure rates converged steadily with stable reliability. Application of 6-sigma continuous improvement tool to the process indicated a further reliability improvement through improved oil lubrication system, especially in the thrust bearing. This showed that increased enlightenment campaign among the various stakeholders in automobile industries will improve on the choice of reliable mechanical crankshafts. © 2014 The Authors.