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- ItemOpen AccessElectrical Properties of Silver Impurities and their Annealing Behaviour in p-Type Fz Silicon(Journal de Physique III, 1691-12) Adegboyega, G.A; Passari, L; Butturri, Maria Angela; Poggi, AntonellaThe electrical activity of silver as well as its annealing properties in 10 Omega cm p-type Fz silicon substrate are studied by means of the four-point probe and minority carrier lifetime measurements. Silver atom concentration in the range 10^{14} to 10^{15} cm^{-3} consistently showed a donor type behaviour in the material and its presence led to a reduction of up to two orders of magnitude in the lifetime of minority carriers by the formation of deep-level traps. Isochronal annealing of silver contaminated specimens showed some gettering of the Ag impurities with resulting temperature dependent changes in the resistivity as well as the minority carrier lifetime values. Analysis of our results shows that a large fraction of the silver impurity atoms present forms the deep level defects and both the deep- and donor-levels appear to originate from the same source
- ItemOpen AccessNot by Bread Alone(Obafemi Awolowo University Press, 1971-11-30) Howat, G. R.The growth in the consumption of bread, in the past ten years is associated with its convenience both in urban and in rural conditions. Bread is in fact the prime example of the silent revolution in eating habits that is now in progress in Nigeria. You can buy bread-wrapped bread, too, which is a hygiene plus-over the whole of Nigeria. It is now a regular item of diet of the urban dweller whether in the North or in the sophisticated South. It is eaten by children, by lorry drivers, by nursing mothers, by labourers, by students, indeed the entire range of social classes. Its convenience, its keeping ability ("shelf life" to the food technologist) and its relative cheapness have enabled it to become big business. The figures speak for themselves. In 1965, the value of the imports of wheat and wheat flour and similar products amounted to just over £3.5 million. By 1970, they had increased to £7,979,000, more than one hundred percent. No precise figures are available to indicate how much of this import goes into the baking of bread by professional bakers. One has to bear in mind that there is now a sizeable industry in biscuit production and that domestic and professional catering absorb a significant quantity. If we assume that the bread baking industry accounts for about eighty percent of the total wheat imports this means that for 1970, £6.4 million was used to import flour for bread-making. By any standard that is a lot of foreign currency for one item of food. It is indeed the largest single food import and on the evidence of the past ten years it is likely to become larger still. In such a situation it is inevitable that the minds of food technologists and of statesmen should turn towards import substitution programmes.
- ItemOpen AccessAgricultural Mechanisation in Nigeria: the Prospects and Promises(Obafemi Awolowo University Press, 1977-10-20) Makanjuola, G. A.The application of technological innovations to the solution of problems is perhaps the single most important factor responsible for human progress. This inaugural lecture addressed: importance and role of agricultural mechanisation as a vehicle for agricultural production; problems faced by Agricultural Engineering as a profession; present state of mechanisation in Nigerian agriculture; type and level of mechanisation appropriate to our farming system; contribution of the University of Ife to agricultural mechanization in Nigeria; and challenges of ensuring that our future mechanisation programmes are meaningful and fruitful.
- ItemOpen AccessA Catalogue of Alternatives(Obafemi Awolowo University Press, 1979-06-12) Sanni, S.AThe effects of Chemical Engineering are less obvious but are just as all-pervasive and growing infiltration of the products of engineering and technology into every home, and to the fact that our lives are more and more conditioned by engineering and technology. This is particularly true of the so-called Less Developed Countries. Consequently, indiscriminate pursuit of advanced technologies by these countries without adequate attention to the human and environmental problems are giving rise to a number of social and psychological maladies, the gravities of which are evident in our craze for imported products.
- ItemOpen AccessTreating Rural Water without Introducing Harmful Substances(Faculty of Agriculture, University of Ife, 1980) Ogedengbe, O.The coliform count on the stream water studied was high. The water is a direct source of drinking water to some rural communities. A previous study established that about 100 ppm of chlorine in the form of chlorox was sufficient to bring: the coliform Most Probable Number (MPN) from about 11,000 per l00ml down to within allowable standard of one per l00ml of water sample. There is some concern that turbid water contains organic matter which when chlorinated could give rise to formation of chloroform and possibly other chlorine-based compounds of the trihalomethane family which conceivably could be carcinogenic. This prompted design and construction of a simple system of turbidity removal and chlorination. With this system the required chlorine dosage even went down to about -50 ppm.
- ItemOpen AccessStudy of Safe Separation Distances between Rural Wells and Neighbouring Soak-Away Systems(Faculty of Agriculture, University of Ife, 1981) Ogedengbe, O.It is becoming increasingly common for educated Nigerians to build houses in rural and semi-urban areas of the country. The plan of a typical modern house includes construction of a septic tank and soakaway for disposal of wastewaters. Very often, a well is dug on the same plot of land for supply of water in lieu of tap water supply. If the homeowner knew that the soak-away system could contaminate his well-water, he might be able to arrange the structures so as to put a safe distance between his well and his soak-away unit. The study reported in this paper shows that in a silty sand soil, the safe separation distance is about 14 meters.
- ItemOpen AccessStudies on the Effect of Conditioning Processes on the Field Drying time of Forages(Faculty of Agriculture, University of Ife, 1983) Ajibola, O. O.The effects of conditioning processes, underlying layer and weather factors on field drying rate of alfalfa were investigated. Drying of chopped, macerated and dewatered alfalfa was affected progressively by the intensity of the change in physical characteristics and inversely by the rate of moisture transfer from the underlying surface. The depressing effect on the drying rate of rolling the macerated and dewatered samples into sheets approximately 6mm thick, was more noticeable on a wetter underlying surface.
- ItemOpen AccessCancer in our Society(Obafemi Awolowo University Press, 1983-11-15) Olusi, S.OIn Nigeria, cancer statistics like any other statistics may be rather nebulous. Just as there are no accurate statistical data on our population figure, there is very little or accurate information on the incidence of cancer in the Nigerian society. However, we know that cancer ranks behind the major causes of death: malnutrition, malaria, infections and infestations and accidents.
- ItemOpen AccessInfluence of Speed and Land Slope on Uniformity of Distribution and Metering of Cowpea Seeds(Faculty of Agriculture, University of Ife, 1985) Saqib, G. S.; Segun, O. O.Investigations were carried out to evaluate the effects of field slope and forward speed on the metering uniformity of the grain drills for planting cowpea. The study was conducted in the laboratory using a John Decre model 8250 grain drill while the field slopes and forward speeds were simulated. The field slopes were varied from zero to 12.5 degrees, while the forward speeds were varied from 3 to 6 km/h. The metering uniformity of the drill was measured in terms of coefficient of variation in the seeds metered and delivered by various seed delivery tubes across the width of the machine. The actual seeding rate delivered by the - grain drill under various field and operating conditions was also determined. Results indicated that the field slope and forward speed had significant effect (p <0.01) on the metering uniformity and seeding rate. There was decrease in the metering uniformity and the seeding rate with an increase in the field slope in the range tested. Similarly, an increase in forward speed resulted in poorer metering uniformity and lesser seeding rate at the field slopes ranging from zero to 12.5 degrees. The interaction between the field slope and the forward speed appeared to be non-significant. Statistical models were developed to predict the metering uniformity and the seeding rate delivered by a grain drill operating at various forward speeds for planting cowpea seeds in sloping lands of Oyo State of Nigeria.
- ItemOpen AccessDesorption Isotherms for Plantain at Several Temperatures(Faculty of Agriculture, University of Ife, 1985) Ajibola, O. O.Moisture equilibrium data for desorption of water from ripe and unripe plantain were obtained at 40°, 50o, 60° and 70o over a range of relative humidities from 10 to 90 percent, using a static gravimetric method. Rite plantain exhibited higher equilibrium moisture content (EMC) than unripe plantain under the same conditions. A non-linear least squares regression programme was used to fit 5 desorption isotherm models to the experimental data and the parameters of the models evaluated. Using the modified Halsey model, the minimum standard error of estimates of the EMC was 1.9% for ripe and 1.4% for unripe plantain.
- ItemOpen AccessEffect of Maize Fermentation on Some Physico-Chemical Properties of 'Ógi'.(Obafemi Awolowo University, 1985) Beckley, Olufela; Adeyemi, I. A.The effect of fermentation or souring period on some physico-chemical properties of ogi, manufactured by the wet- and dry-milling processes from downy mildew resistant white maize variety (DMR white) were evaluated. Determinations were carried out for titratable acidity, starch, diastatic activity, damaged starch, reducing and non-reducing sugars, liquefaction number, Brabender amylograph pasting characteristics and Adam's consistometer value. The results showed that titratable acidity increased from 0.18% to 0.37% lactic acid, while starch content was reduced from 89.2 to 70.5% with period of fermentation, although souring did not produce any appreciable change in starch content. Similarly, there was no appreciable change in diastatic activity, damaged starch and reducing and non-reducing sugars, except for samples fermented or soured for six days. Amylograph peak viscosity was higher for wet-milled ogi than dry-milled ogi being in the range of 1030 to 1250 B.U. and 210 to 960 B.U. respectively. Peak viscosity was observed to increase with souring period of maize flour. Set-back value, index of gelatinization and Adam's consistometer value were observed to decrease with either fermentation or souring period. The use of souring water in preparing ogi porridge, appreciably increased its titratable acidity, but produced ogi of poorer pasting viscosity.
- ItemOpen AccessA Computer Simulation Model of Optimum Sized Tractor Selection for Agricultural Mechanization(Obafemi Awolowo University, 1985) Adagunodo, Emmanuel Rotimi; Jaiyesimi, S. B.; Mensah, E. K.A computer simulation model for the selection of optimum-sized tractors based upon the durability and minimum cost analysis of the tractor has been developed. There is the need to optimize tractor sizes so as to minimize the cost and increase the productivity of farm mechanization process. The optimal replacement period and reliability of the tractor are considered in this study with respect to the volume of utilization of such tractor. A procedure for determining tractor optimum size through the replacement period and reliability analysis is presented in the study. The results of the study establish that two tractor models - David Brown 995 and 990 - of 62 and 58 horsepower respectively are recommended for the two categories of tractor owners and users involved in the study. DB 995 has been considered adequate for the private commercial farmers who cultivate between (30-40) hectares of land and DB 990 is recommended as the optimum machine for the government-owned tractor hiring units. The results of the work show further that a few policy implications may arise from changes in the two important quantities - maintenance and purchase costs of the tractor. A low maintenance and high purchase costs lead to extended replacement period and high durability. On the other hand, high maintenance and cheap purchase price of the tractor result in shortened replacement period and low durability for the tractor. The need to stop any subsidies on tractor purchase price and provide subsidized maintenance and repairs and also establish more government-owned tractor hiring units is stressed in the study.
- ItemOpen AccessExtrusion Characteristics of Cereal and Legume Flours.(Obafemi Awolowo University, 1985) Akinjayeju, Oluwole; Onayemi, O.Some physical factors that determine the extrusion characteristics of cereal-legume blends were examined. These were particle size, substitution level and type of legumes. Corn (Zea mays L.), Cowpea (Vigna unguiculata) and Winged beans ( Psophocar tetragonolobus L.) of three particle sizes namely flour (<:425 microns), grits (>425 microns, <600 microns) and coarser grits (>600 microns,< 850 microns) were used. Blends containing 10% and 20% of each legume with the respective corn fraction were prepared and analysed for proximate composition, water absorption capacity, pasting (cooking) characteristics and viscosity. Addition of legumes increased the nutritional composition of corn-meal with more increases in corn-winged bean than corn-cowpea blends. Winged bean produced greater adverse effects on viscosity and pasting characteristics of corn-legume blends than did cowpea. Statistical analysis showed that the type of legume had the greatest effect on most of the characteristics examined while substitution level produced the least effect. The CWBF (80:20), CWBG 600 (80:20) and CBG 600 (80:20) blends would most probably give the best extruded products since these blends would be able to withstand extrusion conditions of high shear and pressure. The CWBF (80:20), CWBG 600 (80:20) and CBG 600 (80:20) blends would most probably give the best extruded products since these blends would be able to withstand extrusion conditions of high shear and pressure.
- ItemOpen AccessDesign of an On-line Library Cataloguing System.(Obafemi Awolowo University, 1985) Faleye, Emmanuel Omoniyi; Jaiyesimi, S. B.The work reported in this thesis is on the design of a portable on-line library cataloging system (including serials' cataloging and binding subsystem) for possible implementation at the University of Ife library. In on-line catalog systems, instead of writing records for each book onto cards (i.e. card catalogs used presently at University of Ife libraries) and transferring these cards onto the entry card catalog shelves (author catalog shelf, title catalog shelf and subject catalog shelf), only one record needs be written onto a random storage device. But this one record is indexed so that it can be found by the use of any one of the access keys for which separate card catalogs are created in a conventional system. All records in the file are easily accessible and the whole file is consequently available for machine searching in response to each interrogation from a terminal. The various programs were developed and implemented on the TRS-80 model II micro Computer with their sample outputs in Appendix C.
- ItemOpen AccessRecovery of Heavy Oil from Nigerian Tar Sands.(Obafemi Awolowo University, 1985) Dawodu, Olukayode Fatai; Oshinowo; AdemodiSolvent extraction of heavy oil from Nigerian tar sands has been investigated using toluene. Pulverization, followed by sieving of the tar sand resulted in spherical agglomeration of the tar sand particles. The agglomeration was found to beneficiate the tar sands in terms of increased percent oil content to the tune of and 13% for the rich and lean tar sands respectively. The effects of solid/liquid ratio, temperature and agitation on the extraction process were evaluated factorial experimental design. Extraction efficiency was found to increase with increasing agitation speed and cuss transfer driving force, expressed in terms of solid/ liquid ratio, but decreased with increasing temperature. Of the three variables, the solid/liquid ratio the greatest effect on extraction efficiency. The rate of oil extraction, expressed as extractibility showed a great dependence on agitation. Twelve and thirteen fold increases creases in extractibility were obtained at solid/liquid ratios of 1/20 and 1/5 respectively for 2.8 fold increase in agitation (250 r.p.m to 700 r.p.m). The asphaltenes content of the heavy oil extracted at 50C was about 12% lower than that of the heavy oil extracted at 25°C for extraction times below 10 minutes. The implication of this reduction in asphaltenes level could be very significant in terms of the cost of upgrading the heavy oil. Stage-wise extraction gave high extraction efficiency at a low solid/liquid ratio. An efficiency of about 99 was obtained at a total, solid/liquid ratio of 2/3 w/v (43wt% solid loading) and agitation speed of 430 r.p.m in a three stage extraction. From an analysis of the power consumed and time ±or extraction, it was found that 440 r.p.m, 26 minutes and 440 r.p.m, 18 minutes could be the most economical agitation and time levels of operation at solid/liquid ratio- of 1/5 and 1/20 respectively.
- ItemOpen AccessAnalysis of Microbial Growth and Product Formation Data Using Modified Pirt's Model.(Obafemi Awolowo University, 1985) Agho, Godfrey Nosakhare; Layokun, S. K.The 'true' biomass and product energetic yield coefficients and the maintenance coefficient for different microorganisms have been determined by analysing data on microbial growth, with and without product formation, using modified Pint's model. The data of kappeli and Fiechter for the aerobic growth of Trichosporun cutaneum on glucose in continuous culture and those of Duvnjak et al for the anaerobic growth of various strains of Saccharomyces and Kluyveromyces on Jerusalem artichokes in batch culture were analysed. Material and energy balances were carried out and these with identified regularities were used to establish the consistency of the data and also used to identify probable sources of measurement errors and outlier data points. The estimates of the yield and maintenance coefficients, obtained using the modified Pirt's model, are presented improved estimates are obtained using covariate adjustment method. The values of the true biomass yield and the maintenance coefficients obtained from the analysis of the data of T. cutaneum are 0.668 and 0.007 respectively. These values compare favourably with those reported for candida utilis which is used for biomass (single cell protein) production. Analysis of the growth studies on Jerusalem artichokes show that the microorganism, K. fragilis 105, may be the best for ethanol production on this substrate. The method used in this work will have applications in the selection of new strains of microorganisms.
- ItemOpen AccessThe Design of an Integrated Database Management System for a Nigerian University Environment.(Obafemi Awolowo University, 1985) Fisusi, Zaccheaus Rotimi; Daini, O.A.The rapid growth in the size and complexity of the Nigerian University demands a more effective and efficient information management technique than has been available or necessary in the past. In some Nigerian Universities at present, computer-based data files are established to serve personnel, payroll and student application needs. Data is selectively and frequently copied from source files and merged with transactions to construct new files appropriate for the application. In this project, an attempt has been made to design an Integrated Database management system that combines the transactions in the Personnel, payroll and student application' areas in a Nigerian University to replace the present separate file method approach for each application area. The approach is based on the concept of Relational Database model, starting with the construction of relationship graphs and entity-relationship model diagrams in the Information Structure design phase and ending with the definition of the conceptual scheme in the Information Structure Implementation phase.
- ItemOpen AccessDigital Simulation of Stochastic Differential Equations.(Obafemi Awolowo University, 1985) Adewumi, David Olambo; Jaiyesimi, S. B.The study of stochastic differential equations started with mathematicians using them as tools in the solution of physical problems. In science and engineering, s.d.e. arises in a natural phenomenon known as "white noise". Some of the major works done in this area of study has been in the analytical solution of s.d.e., very little attention has been paid to digital simulation techniques. In this thesis we have evolved a digital and analog simulation technique for solving s.d.e s. We have used the TRS-80 model II microcomputer system at the University of Ife, Nigeria and the 680 analog/parallel logic computer system of the University of Sussex; U.K. in our digital simulation procedures. We have used the improved Euler’s and Runge-Kutta's methods of numerical integration. We have solved some problems in science and engineering using the digital simulation techniques evolved. These problems are s.d.e. describing: the white noise, the Lagevin's equation, the influence of a rapidly fluctuating density of the earth on the motion of a satellite in a circular orbit, the motion of a rigid body rotating under a random force, the Fokker-Planks equation. We have also considered the convergence of the results and the probable error in the simulation experiments.
- ItemOpen AccessThe Development, Construction and Evaluation of a Micro-spray Dryer(Obafemi Awolowo University, 1985) Anjorin, Mojisola Oluyemisi; J., WypychA co-current laboratory spray dryer was designed to meet multipurpose requirements for drying food materials and constructed from relatively cheap locally available materials. Tests, on the basis of 100% moisture were carried out to characterise the equipment and milk was dried to determine the particle size distribution. The dryer efficiency at optimum conditions, varied between 44.7%-59.7% and the average particle size was 10ym - 20um. The highest temperature of the air possible for drying was 413K while the lowest was 355K and the maximum air flow rate in the chamber was 31 litres/minute. The drying rate was 0.65g/min and, the maximum relative humidity of the outgoing air at the minimum temperature was 96%.
- ItemOpen AccessProgramming the Unprogrammable(Obafemi Awolowo University Press, 1985-06-04) Jaiyesimi, S. BIn this lecture I will like to address myself to the 'now-ology' (so to speak) of our society and the possible futuristic fifteen years ahead. Major trends in computing are expected to develop in this period, and may become very significant for mankind. This is important because it is considered that many of the changes that will occur after 1990 need to be taken into account when formulating policy for the subsequent ten years. The essential prerequisite to the formulation of a general policy must be the study and the thorough evaluation of policy alternatives. Such studies are particularly necessary in the case of computing because the situation is changing so rapidly that the formulation of a forward-looking policy is extremely difficult.