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112 results on '"Ostfeld, Avi"'

1. Relax-Tighten-Round Algorithm for Optimal Placement and Control of Valves and Chlorine Boosters in Water Networks

Author

Pecci, Filippo, Stoianov, Ivan, and Ostfeld, Avi

Subjects
Mathematics - Optimization and Control
Abstract

In this paper, a new mixed integer nonlinear programming formulation is proposed for optimally placing and operating pressure reducing valves and chlorine booster stations in water distribution networks. The objective is the minimization of average zone pressure, while penalizing deviations from a target chlorine concentration. We propose a relax-tighten-round algorithm based on tightened polyhedral relaxations and a rounding scheme to compute feasible solutions, with bounds on their optimality gaps. This is because off-the-shelf global optimization solvers failed to compute feasible solutions for the considered non-convex mixed integer nonlinear program. The implemented algorithm is evaluated using three benchmarking water networks, and they are shown to outperform off-the-shelf solvers, for these case studies. The proposed heuristic has enabled the computation of good quality feasible solutions in most instances, with bounds on the optimality gaps that are comparable to the order of uncertainty observed in operational water network models.

Published
2020
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2. A Review of Cybersecurity Incidents in the Water Sector

Author

Hassanzadeh, Amin, Rasekh, Amin, Galelli, Stefano, Aghashahi, Mohsen, Taormina, Riccardo, Ostfeld, Avi, and Banks, Katherine

Subjects
Computer Science - Cryptography and Security
Abstract

This study presents a critical review of disclosed, documented, and malicious cybersecurity incidents in the water sector to inform safeguarding efforts against cybersecurity threats. The review is presented within a technical context of industrial control system architectures, attack-defense models, and security solutions. Fifteen incidents were selected and analyzed through a search strategy that included a variety of public information sources ranging from federal investigation reports to scientific papers. For each individual incident, the situation, response, remediation, and lessons learned were compiled and described. The findings of this review indicate an increase in the frequency, diversity, and complexity of cyberthreats to the water sector. Although the emergence of new threats, such as ransomware or cryptojacking, was found, a recurrence of similar vulnerabilities and threats, such as insider threats, was also evident, emphasizing the need for an adaptive, cooperative, and comprehensive approach to water cyberdefense.

Published
2020
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6. Future Water: A Multi-University International Web Seminar.

Author

Pointl, Michael, Marques, João, Pick, Frances C., Salcedo, Camilo, Vertommen, Ina, Zeidan, Mohamad, Boxall, Joby, Cunha, Maria C., Fuchs-Hanusch, Daniela, Jung, Donghwi, Ostfeld, Avi, Saldarriaga, Juan, and Lansey, Kevin E.

Subjects
WEBINARS, WATER supply, TRANSBOUNDARY waters, CLIMATE change adaptation, WATER management
Abstract

Historically, water utilities have relied on tried-and-true practices in the design and operation of their infrastructure, tapping new resources and expanding networks as needed. However, as the effects of climate change and/or urbanization increasingly impact both water supply and demand, utilities need new, holistic planning and management approaches. Integrated planning approaches must account for changing policies, technological progress, and unique, setting-specific operating conditions. Based on this notion, an international web seminar with faculty, researchers, and students from nine universities across five continents was conducted. In the 3-month seminar, participants were split into groups and tasked with developing future-proof, sustainable water management solutions for fictitious settings with unique resource availability, climate change predictions, demographic, and socioeconomic constraints. The goal of the seminar was to combine participants' unique perspectives to tackle challenges in developing future water infrastructure, while forming lasting relationships. Water management concepts became more daring or "out-of-the-box" as the seminar progressed. Most groups opted for a holistic approach, optimizing existing infrastructure, integrating decentralized water management, furthering digitization, and fostering the adoption of innovative policy and planning strategies. To gauge their impact on the evolution of ideas, group dynamics and communication were observed throughout the seminar. As a result, the findings serve not only as a compendium of ideas and concepts for holistic design in the water sector, but also facilitate international collaboration, improve communication in cross-cultural teams or guide the development of training programs in water management for researchers, professional engineers, or water utilities. [ABSTRACT FROM AUTHOR]

Published
2024
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17. Improving Multi-Objective Optimization Methods of Water Distribution Networks.

Author

Kidanu, Rahel Amare, Cunha, Maria, Salomons, Elad, and Ostfeld, Avi

Subjects
WATER distribution, EVOLUTIONARY algorithms, PROBLEM solving
Abstract

Water distribution network design is a complex multi-objective optimization problem and multi-objective evolutionary algorithms (MOEAs) such as NSGA II have been widely used to solve this optimization problem. However, as networks get larger, NSGA II struggles to find the diverse and uniform solutions that are critical in multi-objective optimization. This research proposes an improved version of NSGA II that uses three new-generation methods to target different regions of the Pareto front and thus increase the number of solutions in critical regions. These methods include saving an archive, local search around extreme and uncrowded Pareto front, and local search around the knee area of the Pareto front. The improved NSGA II is tested on benchmark networks of different sizes and compared to the best-known Pareto front of the networks determined by MOEAs. The results show that the proposed algorithm outperforms the original NSGA II in terms of broadening the Pareto front solution range, increasing solution density, and discovering more non-dominated solutions. The improved NSGA II can find solutions that cover all parts of the Pareto front using a single algorithm without increasing computational effort. [ABSTRACT FROM AUTHOR]

Published
2023
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41. Improving Contamination Detectability in Water Distribution Systems using Active Fault Detection

Author

Lifshitz, Ron, Ostfeld, Avi, Vrachimis, Stelios G., Eliades, Demetrios G., Polycarpou, Marios M., Polycarpou, Marios M. [0000-0001-6495-9171], Eliades, Demetrios G. [0000-0001-6184-6366], and Vrachimis, Stelios G. [0000-0001-8862-5205]

Abstract

Contamination event detection in Water Distribution Systems (WDS) is an important part of the overall procedures followed by operators to ensure the delivery of safe drinking water to consumers. In practice, detection methodologies may use a small number of sensors, which may be placed optimally throughout the network, to monitor water quality. Typically, due to their high costs, only a small number of these sensors are available within each WDS, and as a result, a part of the network is not monitored by sensors. In this paper, we propose a novel methodology for detecting contamination events by increasing the area monitored by these water quality sensors. Specifically, the proposed methodology can be used in emergency cases when information is available about a possible contamination event in the system, to actively manipulate WDS actuators, by closing and opening valves, and alter the flow directions within the network. This is based on the concept of Active Fault Detection, in which the control input of a system is modified with the aim to improve detectability of a fault. This active detection scheme, drives flows from specific parts of the network in pre-determined paths, to allow the sensors to monitor the quality of water from previously unobserved parts of the network. As a result, the monitoring coverage of the sensors is increased and some contamination events occurring within those areas can be detected. Moreover, the methodology facilitates the isolation of the contamination propagation path and its possible source. We demonstrate how such goals can be achieved on two simple example networks, discuss the benefits of the results and open the discussion for further work in this area.

Published
2018

44. A versatile and low-cost open source pipetting robot for automation of toxicological and ecotoxicological bioassays

Author

Steffens, Sebastian, primary, Nüßer, Leonie, additional, Seiler, Thomas-Benjamin, additional, Ruchter, Nadine, additional, Schumann, Mark, additional, Döring, Ricarda, additional, Cofalla, Catrina, additional, Ostfeld, Avi, additional, Salomons, Elad, additional, Schüttrumpf, Holger, additional, Hollert, Henner, additional, and Brinkmann, Markus, additional

Published
2017
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