International Journal of Engineering Research in Africa Vol. 10

Abstract: The production of metallic iron from iron oxide using end-of-life tyres (RT) and its blends with metallurgical coke as reductants has been investigated through experiments conducted in a laboratory scale horizontal tube furnace. Composite pellets of iron oxide (96.89 % Fe₂O₃) with RT, coke and coke/RT blends (in four different proportions) were rapidly heated at 1500 °C under high purity argon gas and the off gas was continuously analysed for CO and CO₂ using an online infrared gas analyser (IR). The extent of reduction after ten minutes, level of carburisation of the reduced metal and the total amount of CO₂ emissions were determined for each carbonaceous reductant. The results indicate that metallic iron can be effectively produced from Fe₂O₃ using RT and its blends with coke as reductant. The extent of reduction and level of carburisation are significantly improved when coke is blended with RT. Blending of coke with RT resulted in significant decrease in CO₂ emissions.

Abstract: Carbon-Carbon composite (C/C) substrate materials are prone to severe oxidation and volatilization problems. To address these issues mullite/SiC coatings were deposited on C/C composite. The coatings were applied by a two-step approach; pack cementation and silica sol based slurry-coating processes. The pack mixture composition for SiC coating comprised; 15-50 wt. % Si (75 μm), 0-25 wt. % B (38.2 μm), 0.01-3 wt. % SiO₂ (38 μm) and 40-85 wt. % SiC green (20 μm). Laboratory synthesized mullite via sol-gel (SG) process of different Al₂O₃/SiO₂ ratios (containing approx. 84-72wt. % Al₂O₃) based on stoichiometric calculation were used; these were admixed with silica sol to form a slurry. The pack mixture and the silica sol based slurry coatings were sintered at temperatures of 1800oC and 550°C respectively. The microstructure and isothermal oxidation behavior of the mullite/SiC coatings and C/C substrates during isothermal oxidation cycle at 1500oC were investigated using XRD and SEM mounted with EDS. Results indicate that optimized oxidation protection for mullite-SiC coating was achieved with higher Al₂O₃ content. The weight loss rate of sol-gel mullite with bulk composition 84 wt. % Al₂O₃ (SG84) was 0.09 gcm-²h^-1 as compared to bulk composition 72 wt. % Al₂O₃ (SG72) which had a weight loss rate of 0.20gcm-²h^-1. The oxidation protection for the synthesized sol-gel mullite/SiC coatings offered effective protection as evidenced in the cycle hour exposure time with limited degradation, chemical compatibility between the coating/substrate interface was good and the phases were quite stable after isothermal oxidation cycle.

Abstract: In this paper, we apply model predictive control (MPC) based on mixed H₂/H to active vibration control of the flexibility of railway vehicle to improve ride quality. However, the flexibility in the body of high-speed railway vehicles creates difficulties which in practice may result in the body structure being heavier than what it is supposed to be. The use of active suspension helps to model the vehicle and its flexibility in an effective manner. Conventional control approaches are compared with linear matrix inequality MPC technique using flexible-bodied railway vehicle as an example. The result indicates that the MPC technique performs better in improving ride comfort compared to the passive and classical techniques when flexible modes are present.

Abstract: Mechanical expression of shea butter from shea kernel (Vitelaria paradoxa) was studied using a 4³ factorial experiment under a Randomized Complete Block Design. The mechanical expression rig comprised an instrumented pistoncylinder assembly in conjunction with a Universal Testing Machine (UTM). Shea butter was mechanically expressed through the perforated base of the press cage cylinder when crushed shea kernel was subjected to uniaxial compressive loading by the UTM. The process conditions were heating temperatures of 50, 70, 90 and 110 °C; applied pressures of 1.5, 2.9, 5.8 and 8.8 MPa and loading speeds of 2.50, 5.00, 7.50 and 10.00 mm min^-1. Heating of the crushed shea kernel samples prior to shea butter extraction was achieved by a temperaturecontrolled band heater enfolding the press cage cylinder. Results showed that a maximum oil yield of 35.10 %, a maximum oil recovery efficiency of 58.50 % and a minimum process loss of 2.83 % were obtained at a heating temperature of about 70 °C, an applied pressure of about 8.8 MPa and a loading speed of about 2.50 mm min^-1.

Abstract: The use of a new quality control (QC) and quality assurance (QA) specification involving Dynamic Cone Penetrometer (DCP) testing in concert with conventional moisture and density testing is becoming more and more frequent in various parts of the world. The need for this additional testing is essential, as the regular in-situ density tests cannot alone ensure the compliance of the layers constructed with the compaction requirements. Recent analyses of the correlation between the DCP testing and the California Bearing Ratio CBR testing show that QC and QA DCP testing is adequate to verify compaction, stability and vertical uniformity in both cohesive and granular soils. Two examples of DCP usage in two Israeli earthwork projects, one of clayey soils and the other of silty-sand soils, indicate the benefits of this usage along with, though for the clayey example only, Falling Weight Deflectometer (FWD) testing.

Abstract: According to the forecast of relevant business data, current jewelry consumption in China and Africa has become increasingly active and has great potential for further development. For now, the industrial value chain of jewelry e-business as a whole is far from a mature state; industry convergence degree is relatively low; market segmentation is high; the demand of customers is large, however the supply is full of chaos. Under the general context of rapid development of e-commerce in the Internet, the structure of jewelry industry requires further adjustment and further improvements. The concept of symbolic consumption has been proposed to highlight the increasing significance of extending symbolic value and experience of the commodity. This paper conducted an innovative and exploratory study on the jewelry B2C business model in China and Africa based on the value of user experience. The contents of this paper include four aspects. Primarily, it analyzes the strengths and weaknesses of jewelry B2C business model. Customers become the main players in the market and can select jewelry products based on their own preferences. Secondly, it explains the value of user experience by exploring the emotions, memories, feelings and deeper identity of value during the consumption process to expand broader space for product value. Furthermore, it provides an explicit analysis of innovative jewelry B2C business model concentrating on combining jewelry with customers' emotions. In addition, it explores the implications of innovative B2C business model in the jewelry industry by creating superior customer experiences.