International Journal of Engineering Research in Africa Vol. 50

Abstract: In this paper we consider the Multi-Aisle Automated Storage and Retrieval Systems where only one Storage/Retrieval machine (crane) is used, which has the advantage of decreasing the system costs but at the same time has the disadvantage of reducing the system throughput. This important performance evaluation parameter is highly related to another equally important one i.e. the cycle time of the crane. Because of its repercussions on the whole system performances, we are interested here in the modeling of this average cycle time, knowing that it could bring positive and significant advantages in terms of efficiency and accuracy, and consequently throughput and productivity. For that, the system to be studied is considered as Discrete Events System. To model it, we use a dedicated graphical tool known under the name Timed Petri Nets in the purpose to explore the theory used to evaluate the performances of these systems.

Abstract: The diversity of enterprise domains is one of the significant factors that add to the challenges confronting organizations when managing compliance, and it, therefore, contributes to the cost of compliance. In particular, there is an indication that the inadequacy of a general approach to analyzing compliance documents impedes adequate compliance management practice. Taking an algorithmic-centric approach to tackling this challenge, this paper proposed algorithms and techniques intended to aid useful extraction, classification and analysis of dataflow, control flow, and time constraints in compliance management domain for different stakeholders. The algorithms and techniques were implemented and validated through two case studies and afterward evaluated for its adoption in practice.

Abstract: The challenge of various methods of analysis of rainfall intensity for design runoff estimation is in the availability of data for the given area. This work aims to evaluate the use of the Intensity Duration and Frequency (IDF) method in design runoff estimation using a rainfall analysis model for low data catchment areas such as Nigeria. The source of the data for the study is the Nigerian Meteorological Agency, and it is for Lokoja, a city in the North Central Zone of the country. Analysis of the data compared to the annual and partial duration series for rainfall intensities at various return periods. Also analyzed was the daily rainfall data to determine the rainfall intensity for the different duration and return periods for the study area. From the analysis, partial duration series analysis offered better design estimates than the annual series. Also noted is the fact that the intensity of rainfall increases with a return period of a given duration. The work also indicates that frequency curves can be used to extrapolate rainfall intensity of a given duration for a longer period than years of record. The paper, therefore, presents a design intensity equation useful for the estimation runoff necessary for sustainable infrastructures such as in water utilization and controls.

Abstract: The main originality of this work consists in investigating low cycle fatigue of cylindrical test piece with wings under imposed constraint and for the temperature 20°c, 200°c, 400°c. Based on a combination between the fatigue parameter of Jiang-Sehitoglu and the relationship of Coffin-Manson, a numerical model for the prediction of the number of cycles at break. It was found that the CuCrZr cylindrical test piece showed a reduction in fatigue life with increasing temperature.

Abstract: This work consists of the study is to analysis by the finite element method the effect of the ageing of the adhesive exposed simultaneously to the temperature and water on the degradation of its mechanical properties and consequently on the transfer of loads from the plate to patch. The stress intensity factor was evaluated according to immersion time and temperature. Several parameters have been taken into consideration, namely the properties of the composite patch, temperature, water absorption, rate and length of crack, the distribution of maximum shear stresses in the adhesive and peel in the patch were also analyzed.

Abstract: There have been growing concerns involving the penetration of Electric Vehicles (EVs) due to the time required by its battery to attain full charge. Interests in EVs had recently experienced a dramatic turn down due to mileage limitation on full battery charge amidst the cost of purchase, but most notably due to the absence of quick chargers that can keep the vehicle on the road within few minutes of arriving at the charging station. Researchers had proposed different charging schemes such as level II ac charging, dc charging, and in some cases, wireless charging schemes that later appear to be inefficient. The use of dynamic or simply road-way powered electric vehicles was also proposed in the literature. However, the proposed cycloconverter-based circuit was simulated in Simulink, and the results obtained proved that the rate of charge increased when compared to the conventional EV charging circuit. Also, the focus is on battery charging technology and battery modeling for application in an electric vehicle

Abstract: A numerical study of the natural convection of laminar heat transfers in the stationary state in a half-elliptic inclined cavity, which represents a continuation of the work done, we studied the influence of the tilt of the cavity by varying the angle — entered 0 degrees, which corresponds to the horizontal cavity, up to 15 degrees. For each value of δ we varied the Rayleigh number from 2.13 10³ to 10⁶. The system of equations governing the problem solved numerically by the fluent calculation code based on the finite volume method. Based on the Boussinesq approximation. Both bottom and upper walls maintained at a constant temperature. The interest of this study is to see the influence of the tilt of the half-elliptic cavity on the structure of the flow and the distribution of temperature. These results can exploited in semi-elliptic agricultural greenhouses that rest on sloping soils. We chose a Prandtl number 0.71 that corresponds to the air. Keywords: Heat transfer; half-elliptical; Natural convection; Laminar flow; Multicellular; CFD simulation

Abstract: Modern multi-area power systems are in persistent facing to imbalances in power generation and consumption which directly causes frequency and tie-line power fluctuations in each area. This paper deals with the load frequency control (LFC) problem where the control objective of regulating their error signals despite the presences of several external load disturbances. It proposes an optimal design of proportional integral derivative controller (PID) based on a novel version of Jaya algorithm called self-adaptive multi-population elitist (SAMPE) Jaya optimizer. A filter with derivative term is integrated with PID controller to alleviate the impact of noise in the input signal. A time domain based-objective functions are investigated such as integral time-multiplied absolute value of the error (ITAE) and integral of absolute error (IAE). Both SAMPE-Jaya and Jaya optimizers are employed to optimally tune the PID parameters for interconnected power systems comprising two non-reheat thermal areas. Three test cases are performed with various load disturbances in both areas individually and simultaneaously. Also, the practical physical constraints related to generation rate constraint (GRC) with its nonlinearity characteristics are taken into account. In addition, the obtained results using the designed PID controller based on SAMPE-Jaya are compared with various reported techniques. These simulated comparisons declare the great efficiency and the high superiority of the designed PID controller based on SAMPE-Jaya.

Abstract: Retracted paper: In high speed machining, performance is generally influenced by the dynamic behaviour of the machine tool structures. The machine tool structure is required to be rigid in order to remove the undesirable vibration and to improve the work piece quality. The most conventional material used in machine tool structure is cast iron which has both stiffness and dynamic characteristics to perform at varying speeds. The objective of this work is to improve damping capacity of vertical machining centre column. The damping capacity of column can be increased further by using passive damping method of ball packing. Damping capacity is a crucial factor which makes the dissipation of vibration happens at faster rate. As compared with cast iron established studies shows that epoxy granite a composite material improves damping capacity. Epoxy granite though could be a good choice for improving the machine tool performance at high speeds but is poor in static stiffness compared to cast iron. In this investigation it was observed that, the static stiffness of epoxy granite composite vertical machining centre column could be increased by using steel reinforcements. The final results reveal that, steel balls with epoxy granite provide faster dissipation time of 15ms at 70% packing ratio as compared to glass balls that showed dissipation time of 35ms. Also it was seen that, the steel balls offer the better damping capacity at optimum packing ratio of 50% mainly due to its specific gravity and mass of the balls.

Abstract: In this paper, we present the transverse shear effect on the plate bending. The element used is a sector finite element called SBSP (Strain Based Sector Plate-Kirchhoff Theory-), it used for the numerical analysis of circular thin plate bending., and it based on the strain approach. This element has four nodes and three degrees of freedom per node. Through the numerical applications with different loading cases and boundary conditions; This makes the present element robust, better suitable for computations.