4 research outputs found
Solving Real-Life Hydroinformatics Problems with Operations Research and Artificial Intelligence
Many real life problems in the hydraulic engineering literature can be modelled
as constrained optimisation problems. Often, they are addressed in the literature
through genetic algorithms, although other techniques have been proposed. In
this thesis, we address two of these real life problems through a variety of techniques
taken from the Artificial Intelligence and Operations Research areas, such
as mixed-integer linear programming, logic programming, genetic algorithms and
path relinking, together with hybridization amongst these technologies and with
hydraulic simulators. For the first time, an Answer Set Programming formulation
of hydroinformatics problems is proposed.
The two real life problems addressed hereby are the optimisation of the response
in case of contamination events, and the optimisation of the positioning of
the isolation valves.
The constraints of the former describe the feasible region of the Multiple Travelling
Salesman Problem, while the objective function is computed by a hydraulic
simulator. A simulation–optimisation approach based on Genetic Algorithms,
mathematical programming, and Path Relinking, and a thorough experimental
analysis are discussed hereby.
The constraints of the latter problem describe a graph partitioning enriched
with a maximum flow, and it is a new variant of the common graph partitioning.
A new mathematical model plus a new formalization in logic programming are
discussed in this work. In particular, the technologies adopted are mixed-integer
linear programming and Answer Set Programming.
Addressing these two real applications in hydraulic engineering as constrained
optimisation problems has allowed for i) computing applicable solutions to the
real case, ii) computing better solutions than the ones proposed in the hydraulic
literature, iii) exploiting graph theory for modellization and solving purposes,
iv) solving the problems by well suited technologies in Operations Research and
Artificial Intelligence, and v) designing new integrated and hybrid architectures
for a more effective solving
State-of-the-Art Report on Systems Analysis Methods for Resolution of Conflicts in Water Resources Management
Water is an important factor in conflicts among stakeholders at the local, regional, and even international level. Water conflicts have taken many forms, but they almost always arise from the fact that the freshwater resources of the world are not partitioned to match the political borders, nor are they evenly distributed in space and time. Two or more countries share the watersheds of 261 major rivers and nearly half of the land area of the wo rld is in international river basins. Water has been used as a military and political goal. Water has been a weapon of war. Water systems have been targets during the war. A role of systems approach has been investigated in this report as an approach for resolution of conflicts over water. A review of systems approach provides some basic knowledge of tools and techniques as they apply to water management and conflict resolution. Report provides a classification and description of water conflicts by addressing issues of scale, integrated water management and the role of stakeholders. Four large-scale examples are selected to illustrate the application of systems approach to water conflicts: (a) hydropower development in Canada; (b) multipurpose use of Danube river in Europe; (c) international water conflict between USA and Canada; and (d) Aral See in Asia. Water conflict resolution process involves various sources of uncertainty. One section of the report provides some examples of systems tools that can be used to address objective and subjective uncertainties with special emphasis on the utility of the fuzzy set theory. Systems analysis is known to be driven by the development of computer technology. Last section of the report provides one view of the future and systems tools that will be used for water resources management. Role of the virtual databases, computer and communication networks is investigated in the context of water conflicts and their resolution.https://ir.lib.uwo.ca/wrrr/1005/thumbnail.jp
Path Relinking for a Constrained Simulation-Optimization Team Scheduling Problem Arising in Hydroinformatics
We apply Path Relinking to a real life constrained optimization problem concerning the scheduling of technicians due to activate on
site devices located on a water distribution network in case of a contamination event, in order to reduce the amount of consumed contaminated
water. Teams travel on the road network when moving from one device to the next, as in the Multiple Traveling Salesperson Problem. The objective, however, is not minimizing travel time but the minimization of consumed contaminated water. This is computed through a computationally demanding simulation given the devices activation times. We propose alternative Path Relinking search strategies exploiting time-based and precedence-based neighborhoods, and evaluate the improvement gained by coupling Path Relinking with state of the art, previously developed, hybrid Genetic Algorithms. Experimental results on a real network are provided to support the efficacy of the methodology