Communities in DSpace

Select a community to browse its collections.

Recent Submissions

Thumbnail Image
Item
Open Access
Influence of titanium solute additions on the microstructural and mechanical behaviours of Ni-B alloys
(Physics and Engineering physics,Obafemi Awolowo University, 2016) Zeblon, Ebimobowei Meshack
The study prepared seven ternary Ni-B-Ti alloys with varying compositions of titanium and one binary Ni-B alloy (control sample). It also determined the solidification path and phase formation of the alloys, their microstructures and their mechanical properties. This was with a view to determining the effect of varying amount of titanium on the microstructure and some mechanical properties of the Ni-B system. The components of the alloys were pure Ni, binary Ni-B containing 18.3wt%B and pure Ti.The components of each alloy were accurately weighed and then melted using an electric furnace. The samples were quenched in air after melting. Differential Thermal Analyzer (DTA) was used to study the solidification path and phase formation of the alloys. The heating and cooling rates ranged from 10-20oC/min. Scanning Electron Microscope (SEM) equipped with Energy Dispersive X-ray Analyzer (EDXA) and Optical Microscope (OM) were used to characterise the structures of the alloys. The sample for SEM and OM investigations were polished, then slightly etched with an etchant consisting of 5g FeCl3+10ml HCl dissolved in 50ml H2O.Instron machine was used to measure the compressive strength of the alloys while the hardness values of the alloys were measured with a micro-hardness tester on the Vickers and Rockwell-C scale. Microscopic and thermal investigations of the alloys revealed the presence of two major primary phases [Ni(α), τ] and other binary and ternary eutectic structures. Microsegregation was not observed in the quenched alloys due to their very high solidification rates. Upon subjection to slow cooling, the microstructures of the alloys becomes complex due to solid-state reactions and large undercoolings in the alloys. The addition of titanium to the Ni-B system led to a shift in microstructure of the alloys from the hypoeutectic to the hypereutectic region during slow cooling. Solid state (eutectoid) transformation of the τ phase was observed in alloys with low titanium contents. But such transformation was not observed for alloys with high titanium contents. The hardness values and Stiffness values of the Ni-B-Ti matrix increased with increase in titanium contents. The study concluded that Ni-B-Ti alloys which were suitable as coating materials to solve wear and abrasive problems in the engineering industries could also be applied to make the materials harder and stiffer.
Thumbnail Image
Item
Open Access
Development of a Synchonous Data Transmission System.
(Obafemi Awolowo University, 1986) Agomo, Uchenna Udochukwu
The development of a 2 - channel synchronous data transmission system is presented. The system is capable of accepting at the input two separate analog voltage signals that have zeroto 1kHz frequency range and amplitude not greater than 2.5 volts. The two analog voltage signals are multiplexed at the input of the-system and converted to corresponding digital representations. These digital representations are then transmitted by means of digital gates from the transmitting section serially and with transmission clock frequency of 6.6 MHz, through cable wire to a remote receiving section, where the received digital representations are re-converted to analog voltage signals and demultiplexed to produce at the output, two separate analog voltage signals plus noise. The noise level does not exceed 5% of the signal level when filtered and leaves analog voltage signals with the same characteristics as those at the input of the system. The designed system is simple and can be used for laboratory demonstration on synchronous data transmission system. It may be useful as a communication medium for data exchange between two data processing terminals. The system may be used to transmit voltage signals from a central storage facility to a remote destination. In such circumstance the signals may be those derived from research results, medical findings and student/staff records. A computer base may then be set up and made accessible to users.
Thumbnail Image
Item
Open Access
Allelopathic Effect of Aqueous extracts of Tithonia rotundifolia (P.M. Blake) and Murraya koenigii L. on the growth and biochemical constituents of Capsicum annuum L. and Corchorus olitorius L.
(Botany,Obafemi Awolowo University, 2012) Tijani, Musa Oyebamiji
The study was conducted to investigate the allelopathic effects of fresh shoot aqueous extracts of Murraya koenigii L. and Tithonia rotundifolia P.M. Blake on the growth and biochemical constituents of Capsicum annuum L. and Corchorus olitorius L. plants. Germination experiment was carried out by raising the seedlings of the two target crops in Petri-dishes lined with Whatman No 1 filter paper and moistened with 10 ml of different concentrations (50% and 100% representing half and full strength) of the aqueous extracts of M. koenigii and T. rotundifolia. For the growth parameters (shoot height, root length, number of leaves, leaf area, leaf area ratio ), yield parameters (fresh shoot and root weight, dry shoot and root weight) and quality parameters (chlorophyll, ascorbic acid and crude protein) analyses, potted plants were separated into the control and two other regimes namely: fresh shoot aqueous extract of T. rotundifolia (FSET) and fresh shoot aqueous extract of M. koenigii (FSEM). The pots were arranged in a completely randomized design. The control plants were supplied with 600 ml of tap water while the extract-treated plants were supplied with 600 ml of the appropriate aqueous extracts daily. Harvesting started at two weeks and continued thereafter on a weekly basis for six weeks. Chlorophyll accumulation, ascorbic acid, percentage nitrogen and crude protein content were determined using standard methods. The data were analyzed using Analysis of Variance (ANOVA) and Least Significance Difference (LSD p < 0.05). The extracts significantly inhibited the germination of the seeds and the plumule and radicle lengths of both target crops. This effect was extract concentration dependent (100% > 50% > Control). The applied extracts of M. koenigii plants significantly promoted virtually all the growth parameters such as shoot height, number of leaves, leaf area, leaf area ratio, fresh shoot weight, fresh root weight, dry shoot weight, dry root weight, chlorophyll a, chlorophyll b, total chlorophyll, ascorbic acid and protein accumulation of the two target crops. The aqueous extract of T. rotundifolia enhanced only the shoot height, leaf area, root fresh weight, chlorophyll a, chlorophyll b, total chlorophyll, ascorbic acid and protein accumulation in the shoot of C. annuum. The root length was however, significantly inhibited by both aqueous extracts. In the case of the potted plants, the effects of the extracts on the various parameters studied followed the order: FSEM > FSET > CONTROL and was target species dependent. The results presented in this work showed that FSEM had more pronounced stimulatory effects on the studied parameters than the FSET. It was evident that while the level of the allelochemicals in the extracts of the two donor plants was phytotoxic to and inhibited the germination and growth of the juvenile seedlings in the Petri-dishes, they, however, had a stimulatory effect on the growth of the matured potted plants as well as on the accumulation of the biochemical constituents studied.
Thumbnail Image
Item
Open Access
Effect of Cassava Peel Ash on the geotechnical properties of some selected Lateritic Soil in Osun State.
(Obafemi Awolowo University, 2015) Mgboh, Chinedu Victor
This study is aimed at assessing the effect of Cassava Peels Ash (CPA) on the stabilization of lateritic soil with a view of improving its geotechnical properties. Lateritic soil samples were collected from three different locations namely, Ife-East, Ayedaade and Olorunda Local Government Areas in Osun state, Nigeria, and were termed sample A, B and C, respectively. Cassava Peels were procured from a local cassava processing factory at Oke-Baale, Osogbo, Osun State. The chemical composition of the soil samples and the CPA, and the geotechnical properties such as grain size, liquid limit (LL), plastic limit (PL), optimum moisture content (OMC), maximum dry density (MDD), California bearing ratio (CBR) and unconfined compressive strength (UCS)of the soil samples were determined in their natural states. The Cassava Peels (CP) were dried and calcined at 700oC for a period of 90 minutes in an electric furnace and the ash produced sieved through 425 µm sieve. The resulting CPA was added to the soil samples in incremental values of 2, 4, 6, and 8% by weight of the dry soil. Each soil sample was equally mixed with 4% lime by weight of the soil. The aforementioned geotechnical properties were determined for each Soil-CPA-Lime mixture. The data obtained from the tests were used to establish the optimum percentage of CPA. The results showed that the soil samples as well as CPA contain between 34 and 42% silicon dioxide. The soil samples are acidic with pH ranging from 4.2 to 5.8. Whereas the CPA is basic (pH = 11.4). On addition of CPA and lime, the LL of sample A increased from 39.0 to 41.2%, sample B decreased from 46.2 to 36.7% and sample C decreased from 35.8 to 33.4% at the ratios of 2, 2 and 4% CPA, respectively. The PI for soil sample A decreased from 3.6 to 1.7%, sample B decreased from 16.1 to 2.3% and sample C decreased from 12.4 to 2.6% at the ratios of 2, 2 and 4% CPA, respectively. The MDD generally increased for all the soil samples as % CPA increased. The MDD increased from 1558 to 2020 kg/m3, 1850 to 2080 kg/m3 and 1110 to 1940 kg/m3at the ratios of 8, 4 and 4 % for samples A, B and C, respectively. The CBR for samples A, B and C increased from 18.0 to 25.0%, 21.0 to 27.0% and 17.0 to 18.0%, at the ratios of 8, 8 and 4% CPA, respectively. The result of the UCS tests generally increased as the % CPA increased. The highest values obtained were 400, 285, 215 kN/m2at the ratios of 8, 8 and 4% CPA for samples A, B and C, respectively. The study revealed that a combination of CPA and lime has the potential of improving the geotechnical properties of lateritic soil but no optimum percentage of CPA could be established for the studied soil samples.
Thumbnail Image
Item
Open Access
Continuous Generalized predictive of an Experiment Four-Tank level Process
(Obafemi Awolowo University, 2016) Olabiyi, Olayinka Ayodeji
The four-tank level process, a typical multi input multi output (MIMO) system exhibit complex dynamics, nonlinearities and strong interaction as seen in most industrial process plants. The complex and dynamic nature of MIMO systems, necessitate the quest for an advanced control technique that could handle strong interactions. In this study, an experimental four-tank system was designed and interface for the implementation of continuous generalized predictive control (CGPC) and other classical controllers for both minimum phase (MP) and non-minimum phase (NMP). The designed and constructed four-tank system was modeled using mass balance and Bernoulli’s law. All components that require high precision were calibrated. The non-linear model of the system was linearized to determine the operating points. State space as well as the transfer function for the two operating phases were obtained. The Relative gain array (RGA) was used to determine a suitable decentralized input-output pairing control structure. Using input-output pairing suggested by RGA, an adopted CGPC algorithm written in MATLAB was employed to design appropriate CGPC loop controllers. Classical PID controllers based on internal model control (IMC) and auto tuning PID were parameterized and implemented on the system. These controllers were used for both the simulation and the real time experiments using MATLAB/Simulink. The controllers’ performance evaluation of the system for both MP and NMP was based on integral absolute error (IAE) and integral square error (ISE) performance indexes and other time-domain performance metrics. The results of the experiments showed that the physical system was adequately matched with the obtained transfer functions. The steps responses obtained for both simulations and experimentations portrait that of an interacting multivariable system. Furthermore, satisfactory performances was achieved for simulation and the real time experiments with comparative lower values of IAE and ISE particularly for the MP. A gross value of ISE 13.63, 9.81 and 54.14 and IAE values of 18.61, 18.52 and 78.14 were for estimated for auto tuned PID, CGPC and IMC respectively. Also, an overall percentage overshoot of 4.91, 3.01 and 5.25% were recorded respectively for MP. On the other hand, larger value of ISE 49.48, 6267.2, 2701, and IAE values of 79.24, 4136 and 1016.4 and percentage over shoot of 0.56, 15.50 and 1.61% were obtained respectively for auto tuned PID, CGPC and IMC respectively for NMP. The newly designed and interface four-tank experimental system will provide a platform to demonstrate and illustrate several control concepts due to its nonlinearity and complex dynamics. The system will help students to connect between control theory and the real-world thereby adding realism to control education. This study established that a satisfactory control response of the four-tank level process can be achieved with CGPC especially when operating at the MP.