École Polytechnique de Montréal

About: École Polytechnique de Montréal is a education organization based out in Montreal, Quebec, Canada. It is known for research contribution in the topics: Finite element method & Computer science. The organization has 8015 authors who have published 18390 publications receiving 494372 citations.

Decoupled Lead Time in finite capacity flowshop: a feedback loop approach

Abstract: Recently studied, Demand Driven Material Requirement Planning (DDMRP) seems to offer good performances. Its buffer parametrization is done by a dynamic adjustment considering the demand evolution, but not the workshop state. Several papers deal with lead time variability and take into account its variations in the parametrization of traditional material management methods such as Material Requirements Planning and pull flow systems. This paper considers lead time variability and proposes a dynamical adjustment of the decoupled lead time of the DDMRP. When applying it to a modified flow shop with a competence bottleneck, results show that the dynamic adjustment of the buffer sizes reduces stocks, while assuring a decent service level. We also find that it increases workload, to an extent where it can be better not to cross a certain limit that has to be determined, otherwise lead times increase drastically.

Uncertainty in chemical process systems engineering: a critical review

Abstract: Abstract Uncertainty or error occurs as a result of a lack or misuse of knowledge about specific topics or situations. In this review, we recall the differences between error and uncertainty briefly, first, and then their probable sources. Then, their identifications and management in chemical process design, optimization, control, and fault detection and diagnosis are illustrated. Furthermore, because of the large amount of information that can be obtained in modern plants, accurate analysis and evaluation of those pieces of information have undeniable effects on the uncertainty in the system. Moreover, the origins of uncertainty and error in simulation and modeling are also presented. We show that in a multidisciplinary modeling approach, every single step can be a potential source of uncertainty, which can merge into each other and generate unreliable results. In addition, some uncertainty analysis and evaluation methods are briefly presented. Finally, guidelines for future research are proposed based on existing research gaps, which we believe will pave the way to innovative process designs based on more reliable, efficient, and feasible optimum planning.

Optical and tribomechanical stability of optically variable interference security devices prepared by dual ion beam sputtering

Abstract: Optical security devices applied to banknotes and other documents are exposed to different types of harsh environments involving the cycling of temperature, humidity, chemical agents, and tribomechanical intrusion. In the present work, we study the stability of optically variable devices, namely metameric interference filters, prepared by dual ion beam sputtering onto polycarbonate and glass substrates. Specifically, we assess the color difference as well as the changes in the mechanical properties and integrity of all-dielectric and metal–dielectric systems due to exposure to bleach, detergent and acetone agents, and heat and humidity. The results underline a significant role of the substrate material, of the interfaces, and of the nature and microstructure of the deposited films in long term stability under everyday application conditions.