Relevance and Applicability of Multi-objective Resource Constrained Project Scheduling Problem: Review Article

Resource-Constrained Project Scheduling Problem (RCPSP) is a Non Polynomial (NP) - Hard optimization problem that considers how to assign activities to available resources in order to meet predefined objectives. The problem is usually characterized by precedence relationship between activities with limited capacity of renewable resources. In an environment where resources are limited, projects still have to be finished on time, within the approved budget and in accordance with the preset specifications. Inherently, these tend to make RCPSP, a multi-objective problem. However, it has been treated as a single objective problem with project makespan often recognized as the most relevant objective. As a result of not understanding the multi-objective dimension of some projects, where these objectives need to be simultaneously considered, distraction and conflict of interest have ultimately lead to abandoned or totally failed projects. The aim of this article is to holistically review the relevance and applicability of multi-objective performance dimension of RCPSP in an environment where optimal use of limited resources is important

Framework for Operational Performance Measurements in Small and Medium Scale Industries Using Discrete Event Simulation Approach

Globally, production systems must cope with limitations arising from variabilities and complexities due to globalization and technological advancements. To survive in spite of these challenges, critical process measures need to be closely monitored to ensure improved system performance. For production managers, the availability of accurate measurements which depict the status of production activities in real time is desired. This study is designed to develop an operational data decision support tool (ODATA-DST) using discrete event simulation approach. The work-in-process and processing time of each workstation/buffer station in a bottled water production system were investigated. The status of each job as they move through the system was used to simulate a routing matrix. The production output data for 50cl and 75cl product from 2014-2016 were collected. A mathematical model for routing jobs from the point of arrival to the point of departure was developed using discrete event simulation. A graphical user interface (GUI) was designed based on the factory’s performance measurement algorithm. Simulating the factory’s work-in-process with respect to internal benchmarks yielded a cycle time of 4.4, 6.23, 5.04 and throughput of 0.645, 0.455, 0.637 for best case scenario, worst case scenario and practical worst case scenario respectively. The factory performed below the simulated benchmark at 26%, 28%, 28% for the 50cl and at 51%, 54%, 59% for 75cl regarding the year 2014, 2015 and 2017 respectively. Performance measurement decision support tool has been developed to enhance the production manager’s decision making capability. The tool can improve production data analysis and performance predictions

Synthesis of supported nickel nanoparticles via a nonthermal plasma approach and its application in CO2 reforming of methane

A microwave plasma treatment was applied to obtain not only a desired strong metal-support interaction but also well-dispersed nickel nanoparticles supported on ceria. The catalytic properties of these supported nanoparticles were tested in CO reforming of methane. The plasma-treated Ni/CeO catalysts showed enhanced turnover frequencies (TOFs), normalized by Ni on the surface, as compared with the thermally calcined samples. The Ni/CeO treated under plasma with low Ni loading gave an enhanced TOF of 9.5 s (700 °C, 50% CH and 50% CO, and 1 atm) as compared with the thermally calcined catalyst (8.7 s). Increasing the Ni loading on the plasma-treated Ni/CeO catalysts gave an improved TOF (10.4 s) which was stable with time, while the TOF was observed to drop by a factor of 2 relative to the optimal TOF on the thermally calcined catalyst after 5 h. For the plasma-treated samples, concurrent treatment of both the uncalcined ceria support and the loaded metal precursor generated strong metal-support interaction and formation of well-dispersed Ni particles, resulting in a superior and stable TOF with time. In the case of thermally calcined catalysts, the weak metal-support interaction and the agglomeration of Ni clusters together with the migration of the Ni particles into the ceria support hindered the accessibility of active nickel sites, resulting in deactivation of the materials during reaction. Moreover, high-resolution transmission electron microscopy, high-angle annular dark-field scanning transmission electron microscopy, H temperature-programmed reduction, and X-ray photoelectron spectroscopy yielded a clear picture of the impact of microwave plasma treatment on the nickel particle size, shape, distribution, and interaction with the ceria support