An Integrated Optimal Control System for Emergency Evacuation

How to effectively control evacuation traffic has emerged as one of the critical research issues in transportation community, due to the unusually high demand surge and the often limited network capacity. This dissertation has developed an integrated traffic control system for evacuation operations that may require concurrent implementation of different control options, including traffic routing, contraflow operation, staged evacuation, and intersection signal control. The system applies a hierarchical control framework to achieve a trade-off between modeling accuracy and operational efficiency for large-scale network applications. The network-level optimization formulations function to assign traffic to different evacuation corridors, select lane reversal configurations for contraflow operations, and identify the evacuation sequence of different demand zones for staged evacuation. With special constraints to approximate flow interactions at intersections, the formulations have introduced two network enhancement approaches with the aim to capture the real-world operational complexities associated with contraflow operations and staged evacuation. The corridor-level optimization formulations, taking the network-level decisions as input, function to identify the critical control points and generate the optimal signal timings along the major evacuation corridors. The formulations feature the critical intersection concept to reduce the interference of side-street traffic on arterial evacuation flows. This study has also developed an efficient solution method using the Genetic Algorithm based heuristics along with an embedded macroscopic simulator. This dissertation has also proposed a revised cell transmission model that aims to capture the complex temporal and spatial interactions of evacuation traffic flows for both levels of optimization formulations. This model can significantly reduce the size of the optimization problem, and yet preserve the ability in effectively modeling network traffic dynamics. Numerical studies were conducted for each individual control component as well as for the entire integrated control system. The results reveal that the staged evacuation and contraflow strategies generated from the proposed formulations can substantially improve the evacuation efficiency and effectively reduce network congestions. Signal control strategies with the critical intersection concept also outperform the state-of-the-practice evacuation signal plans

Systemic approach and decision process for sustainability in chemical engineering: Application to computer aided product design

Dans un contexte de prise en compte croissante des enjeux environnementaux, l'industrie de la chimie et des procédés se retrouve confrontée à des problématiques de substitution de molécules. Les méthodes de formulation inverse, qui consistent en la recherche assistée par ordinateur de molécules satisfaisant un ensemble de contraintes, répondent de manière efficace à ces problématiques. A partir de l'analyse systémique des usages et fonctionnalités nécessaires dans ce contexte, nous développons un outil logiciel de formulation inverse mettant en oeuvre un algorithme génétique. Celui-ci est capable d'explorer un espace de solutions plus vaste en considérant les mélanges et non les molécules seules. Par ailleurs, il propose une définition des problèmes très flexible qui permet la recherche efficiente de molécules issues de filières renouvelables. En s'appuyant sur l'ingénierie système et l'ingénierie d'entreprise, nous proposons un processus formel de prise de décision pour la substitution de produit dans un contexte industriel. Ce processus de décision multi-critères englobe les phases de définition des exigences, de génération de solutions alternatives, de sélection de la meilleure alternative et de mise en oeuvre du produit. Il utilise une approche dirigée par les modèles et des techniques de prises de décision qui garantissent un alignement opérationnel en complément de l'alignement stratégique. A travers un cas d'étude, nous montrons comment l'utilisation conjointe de notre outil de recherche par formulation inverse et de notre processus de décision permet une démarche environnementale de substitution de produit à la fois efficiente et conforme à la réalité de l'entreprise. ABSTRACT : In a context where environmental issues are increasingly taken into account, the chemical related industry faces situations imposing a chemical product substitution. Computer aided molecular design methods, which consist in finding molecules satisfying a set of constraints, are well adapted to these situations. Using a systemic analysis of the needs and uses linked to this context, we develop a computer aided product design tool implementing a genetic algorithm. It is able to explore a wider solution space thanks to a flexible molecular framework. Besides, by allowing a very flexible setting of the problem to be solved, it enables the search of molecules sourced from renewable resources. Based on concepts from system and enterprise engineering, we formalize a decision making process dedicated to the product substitution in an industrial context. This multi-criteria decision process includes the phases of the requirements definition, of the generation of alternative solutions, of the selection of the best alternative and of the product application. It uses a model driven approach and decision making techniques that guaranty an operational alignment in addition to the strategic alignment across the chemical enterprise. Through a case study, we expose how the combination of our computer aided product design tool and our decision making process enables an environmentally compliant approach of product substitution which is both efficient and in adequacy with enterprise context

Hierarchical multi-objective decision making

This paper proposes a hierarchical procedure for solving decision problems with multiple objectives. The procedure consists of two levels, a top- and a base-level. The main idea is that the top-level only provides general preference information. Taking this information into account the base-level then determines a compromise solution. For a multi-objective linear program it will be shown how such a hierarchical procedure can be structured by deriving weight restrictions from the general prefecence information of the top-level and by using the interactive MODM procedure of Zionts and Wallenius

A Holistic Framework For Supply Chain Management

A new approach to Supply Chain Management (SCM) is proposed that considers different structures conceived as module components of a holistic framework. In this way, decision support is supplied at different levels and for different functionality. Thus, the system may be also used for multi-objective assistance to decision making, while systematically considering the time and other intrinsic constraints associated to the structure of the supply chain. This approach is applicable to the different supply chain layers, from the individual single sites to the global Supply Chain optimisation, including multi-site (single company) competitive strategic decisions, or the independent management of a similar objective (i.e. benefits, client satisfaction, etc.) for different companies. © 2003 Elsevier B.V. All rights reserved.14C413418Arntzen, B.C., Brown, C.G., Harrison, T.P., Trafton, L.L., Global supply chain management at digital equipment corporation (1995) Interfaces, 25, pp. 69-93Erengüç, S.S., Simpson, N.C., Vackaria, A.J., Integrated production/distribution planning in supply chains: An invited review (1999) European Journal of Operational Research, p. 115Gimeno, L., Rodrigues, M.T., Sequential Approach to Production Planning in Multisite Environments (2002) 15th IFAC World Congress, , Barcelona, SpainHomburg, C., Hierarchical multi-objective decision making (1998) European Journal of Operational Research, 105, pp. 155-161Mele, F.D., Espuña, A., Puigjaner, L., (2002) Discrete Event Simulation for Supply Chain Management in AIChE Annual Meeting, , (Accepted). Nov. 3-8, Indianapolis, USAVidal, C.J., Goetschalckx, M., Strategic production-distribution models: A critical review with emphasis on global supply chain models (1997) European Journal of Operational Research, 98, pp. 1-1