NETWORK DESIGN UNDER DEMAND UNCERTAINTY

A methodology for network design under demand uncertainty is proposed in this dissertation. The uncertainty is caused by the dynamic nature of the IP-based traffic which is expected to betransported directly over the optical layer in the future. Thus, there is a need to incorporate the uncertainty into a design modelexplicitly. We assume that each demand can be represented as a random variable, and then develop an optimization model to minimizethe cost of routing and bandwidth provisioning. The optimization problem is formulated as a nonlinear Multicommodity Flow problemusing Chance-Constrained Programming to capture both the demand variability and levels of uncertainty guarantee. Numerical work ispresented based on a heuristic solution approach using a linear approximation to transform the nonlinear problem to a simpler linearprogramming problem. In addition, the impact of the uncertainty on a two-layer network is investigated. This will determine how theChance-Constrained Programming based scheme can be practically implemented. Finally, the implementation guidelines for developingan updating process are provided

A simulation-based modelling approach for a production line with nested-loop work sequences

Critical for current situation analysis in lean initiatives, establishing standardised work can be challenging due to the intricacies involved in documenting complex routine work, mainly characterised by nested-loop work sequences. This study aims to extend the existing methods of establishing standardised work and analysing a production line for complex routine work. Novel concepts and terminologies are introduced, combining the existing methods into a modelling approach capable of addressing all complex features simultaneously. A standardised work sequence diagram is defined as a fundamental representation, forming the basis for a new simulation-based modelling approach. Described, validated, and applied through an industrial case study, the proposed approach is confirmed effective, achieving an average relative combined cycle time of 0.99, compared to the expected value of 1. The resulting redesign of standardised work significantly improves line efficiency from 53% to 79%, with a manpower reduction from 8 to 4 workers.</p