Vortrag von Tanka Dhamala und Hari Nath

am 24.06.25 
um 16:00 
in 48-562 

wird Tanka Dhamala einen Vortrag über Evacuation Planning: Multi-Objective Approach halten. Interessierte Gäste sind herzlich willkommen.

Abstract:
One of the most prominent mathematical methods for addressing evacuation planning problems is the use of dynamic network flow models, which aim either to maximize the flow from danger zones to safe areas or to minimize the total clearance time required to evacuate a given population. In this presentation, we adopt a macroscopic modeling approach to represent and analyze these issues. Although network reconfiguration is a computationally challenging task, it can significantly improve evacuation performance by increasing the possible capacity through lane reversals directed toward safe destinations. However, implementing a complete contraflow reconfiguration may block most lanes leading toward the source areas, unfortunately blocking some paths for specific applications. We propose strategies to avoid reversing unnecessary arcs
during network reconfiguration.
However, since real-life problems are highly motivated by modeling with multi-criteria models, we combine the above problems with additional characteristics. For example, policymakers may wish to keep some paths upturned from a given junction or a set of intermediate nodes. Regardless of flow maximization or time minimization, this requirement implies that the flow is decreased and the evacuation time is increased. We present the existing algorithms using bi-objective programming approaches. On the other hand, we model the multi-terminal problems where Pareto optimal solutions for the maximization of sinks are obtained, contrary to the priority-based lexicographically maximum flow solutions at sinks.

Hari Nath wird einen Vortrag über Network Flow Location Problems with Maximum Utility of the Facilities: A Bicriteria Approach halten. 

Abstract:
This study addresses FlowLoc problems on directed networks, which involve optimally placing facilities of given sizes on arcs to minimize disruption to network flow and maximize the utility of the facilities placed. Each facility is associated with a nonnegative utility, and the problem is formulated as a bicriteria optimization model aiming to maximize both flow (static/dynamic) and total utility of the facilities placed. We propose an epsilon-constraint-based algorithm to obtain exact Pareto optimal solutions and develop an NSGA-II-based approach to generate nondominated solutions that progressively approximate the true Pareto front over generations. Through computational experiments on the road network of Bhaktapur city, Nepal, we find that the NSGA-II algorithm is more efficient for larger problem instances, where the epsilon-constraint method either becomes too timeconsuming or the MILP-solver used in its subroutines fails to deliver a solution.