International Journal of Engineering Research in Africa Vol. 52

Abstract: This paper proposes a mathematical model for production scheduling, whose objective is to maximize the profits or Throughput of a company in the food sector through a Flexible Hybrid Flow, based on the theory of constraints. Considering the company's production configuration, which is a two-stage hybrid flow line, a mixed integer linear model programming (MILP) was formulated and programmed to adequately represent the real situation. The mathematical model developed in this study that is an easy and effective tool that helps to control the production process, by optimizing the quantities of each product to be produced, as well as establishing the sequence in which they must be carried out, which becomes an advantage against its competitors and also obtain a timely response to the needs of demand and compliance with the commitments made to its customers. The results obtained with the MILP, with reasonable computational times, allow for maximizing profits, considering the constraints of the problem.

Abstract: Quality of Infrastructure became indispensable to the innovation-driven development. Poor infrastructure quality means more extra costs for operation and maintenance, in addition to un-studied impacts on the surrounding environment and society. To eliminate the bad impacts and the extra costs, sustainability must be applied in all infrastructure projects. Sustainability represents one of the latest degree subjects that have various trials to connect the social science with the engineering and the environmental science with the future technology. The objective of this research is to provide an integrated sustainable evaluation system (ISES) for quantifying all impacts of road projects. The proposed evaluation system took into consideration the different phases of project including construction phase and operational phase. The different impacts of road projects were divided into three main classifications; the project economic costs to include costs of project construction and operation; the environmental impacts; and the social impacts. Furthermore, a real case study was discussed to validate the research methodology, where it was concluded that the environmental and social impacts have the main impact on project decision and according to the ISES value, the case study road has a sustainable impact on the surrounding environment and society.

Abstract: Aluminum alloys have been attracting significant attention. Especially Al-Mg-Si alloys can exhibit an excellent balance between strength and ductility. Deformation mechanisms and microstructural evolution are still challenging issues. Accordingly, to describe how the type of phase influence mechanical behaviour of Al/Mg/Si alloys, in this paper atomic simulations are performed to investigate the uniaxial compressive behaviour of Al-Mg-Si ternary phases. The compression is at the same strain rate (3.10¹⁰ s−1); using Modified Embedded Atom Method (MEAM) potential to model the deformation behaviour. From these simulations, we get the total radial distribution function; the stress-strain responses to describe the elastic and plastic behaviors of GP-AlMg₄Si₆, U2-Al₄Mg₄Si₄ and β-Al₃Mg₂Si₆ phases. For a Detailed description of which phase influence hardness and ductility of these alloys; the mechanical properties are determined and presented. These stress-strain curves obtained show a rapid increase in stress up to a maximum followed by a gradual drop when the specimen fails by ductile fracture. From the results, it was found that GP-AlMg₄Si₆ & U2-Al₄Mg₄Si₄ phases are brittle under uniaxial compressive loading while β-Al₃Mg₂Si₆ phase is very ductile under the same compressive loading. The engineering stress-strain relationship suggests that β-Al₃Mg₂Si₆ phase have high elasticity limit, ability to resist deformation and have the advantage of being highly malleable. Molecular dynamics software LAMMPS was used to simulate and build the Al-Mg-Si ternary system.

Abstract: The present research work is concerned with the construction of road embankments on a Sabkha soil in Algeria. This soil is not only soft and very humid during the flooding seasons but also has frequent small areas of very soft soil which are called locally weak zones (LWZ) in the context of this study. LWZ are characterized by low strength and high compressibility. Two-dimensional axisymmetric analyses were carried out using PLAXIS 2D 2017. The study demonstrated that ordinary stone columns (OSC) are ineffective given the nature of these soils due to the excessive bulging caused by the lack of lateral pressure. On the other hand, the reinforced stone columns with external and internal reinforcements called as vertical encasement and horizontal strips (VESC+HRSC) are one of the best improvement methods of locally weak zones (LWZ), especially to increase the stability of embankment on the highway, namely, a much reduced bulging and a reasonable settlement, so that it is possible to build safe and very high embankments (indeed, numerical results showed for a (VESC+HRSC) combination, a vertical settlement of 0.74 m and a lateral deformation of 20.02 mm vs. 1.56 m and 221.16 mm for an OSC). Besides, an extensive parametric study was conducted to investigate the effect of the spacing of the horizontal reinforcing strips and of the column reinforced length. The influence of stone column diameter, depth of locally weak zone, and the effective stiffness of the geosynthetic, on the performance of the (RSC) - embankment composite were also investigated. The computational results are presented in the form of tables and graphs, and compared with previous published results available in the literature.

Abstract: Developing countries are still in the stage of infrastructure construction. For the reasons of design and economy, it is inevitable to encounter large section tunnel when building subway and expressway in urban construction. Taking the tunnel project of Central Park East Station of Chongqing Metro Line 10 as the case background, the cross-section optimization and process optimization of each section in the construction of extra-large cross-section tunnel are studied. Based on the principle of analogy analysis, the optimization model of the super-large section tunnel is constructed from five aspects: horizontal stratification optimization, horizontal block optimization, plane partition optimization, longitudinal section optimization and three-dimensional block optimization. Finally, a better excavation scheme than the original design is obtained by using the plane optimization model. Therefore, it can be used as a reference for similar projects to optimize tunnel construction methods.