An integrated simulation–optimization study for consolidating production lines in a configure-to-order production environment
This study investigates production lines consolidation in a configure-to-order production environment using simulation and optimization strategies. The current production environment has three separate production lines that will be consolidated into two production lines. Two production line configurations are analyzed: product and process layouts. Product layout has a continuous smooth flow, small work-in-process (WIP), short total production time per unit of product, and reduced material handling requirements. On the contrary, process layout offers more flexibility, allows for higher utilization of machines, and requires higher grades of operators’ skills. A simulation-based comparison of the current and future systems is conducted considering lead time, throughput, utilization, and WIP. A mixed integer programming model that optimizes the transportation cost and waiting time is then formulated based on the selected process layout. Simulation results provide recommendations to improve the system level performance measures and support management decisions. The current transportation schedule is ineffective, and hence a real-time dashboard based on the optimization model is suggested. The dashboard will improve communication and transportation between the two production lines.
Multi-item dynamic lot-sizing with delayed transportation policy
We optimize ordering and inbound shipment decisions for a manufacturer that sources multiple items from a single supplier. The objective is to satisfy the requirements in the production plan with minimum transportation and inventory holding costs over a multi-period planning horizon. Transportation costs are charged to the manufacturer on a per truck shipment basis. We investigate the option of delaying a less-than-full truckload shipment to the next period, by utilizing the safety stocks as needed. We analyze the impact of delaying shipments on both cost and service levels in stochastic environments through experiments with data from a bus manufacturer. The results indicate that the proposed policy reduces both holding and transportation costs without creating much stock-out risk.
Characterization of ceramic composite membrane filters for hot gas cleaning
Abstract Novel composite ceramic membrane filters suitable for hot gas cleaning operations have been prepared from fly ash and titania particles on stainless steel woven mesh substrates. Both membranes had a structure like a solid packed bed with a thickness of less than 100 μm. In the domain of laminar flow, significant differences in the pressure drop between experimental results and those predicted from the Kozeny-Carman relationship were found, particularly for flow through the titania membrane. Membrane filters with extremely small pores such as the titania membrane are greatly affected by slip up to 80% in permeability at elevated temperatures. Efficiencies of filtration of typical coal fired power station exhaust fly ashes were found to be greater than 909% for both titania and ash membranes, whilst there was greater variation in the pressure drops in the ash membrane than in the titania at typical gas flows.