Conferences, Lectures, & Seminars
Events for May
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Oral Dissertation Defense
Wed, May 09, 2012 @ 02:00 PM - 03:30 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Maud Comboul, CEE Ph.D, Candidate
Talk Title: Stochastic and Multiscale Models for Urban and Natural Ecology
Abstract:
This research reflects on both particular cases of ecologies: sensor networks in urban water distribution systems and forest dynamics under changing disturbance regime, and the elaboration of exploration tools to investigate and assess those complex ecologies. The predictive models that emerged from this work rely on sophisticated computer simulations designed based on stochastic and multiscale principles, and contribute to characterizing and evaluating the knowledge and information that is available about the systems under investigation. This thesis is organized into three distinct projects, each of which confronts specific challenges encountered when modeling complex systems. The first project considers the monitoring of water distribution networks where we describe a stochastic parameterization and analysis of uncertainty for the design of single-stage as well as two-stage sensor networks aimed at maximizing the probability of detection of accidents and intrusions in water distribution systems. Next, this study explores the ecological and evolutionary impacts of different disturbance regimes (generated following a stochastic Poisson process) on forests using the framework of a spatially explicit and individual-based forest model designed around four functional traits of trees. The final project investigates a multiscale characterization of forest dynamics using Monte-Carlo simulations of the fine scale dynamics to synthesize a coarse-grain stochastic model describing the dynamics of the system on larger spatial scales. In addition to modeling aspects, all three projects yield adequate computational performance, thereby assessing a recurrent challenge associated with the computational feasibility and performance of relevant numerical algorithms.
Advisor: Dr. Roger Ghanem
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani Civil and Environmental Engineering Seminar
Mon, May 14, 2012 @ 01:00 PM - 02:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Felipe de Barros, Department of Geotechnical Engineering and Geosciences,Technical University of Catalonia, Barcelona (Spain)
Talk Title: A health risk-driven approach for hydrogeological site characterization
Abstract: Obtaining accurate predictions of human health risks from groundwater contamination is a challenge. The main difficulty relies on the fact that many of the components that constitute human health risk assessment are uncertain and requires interdisciplinary knowledge. Amongst these, we highlight two classes of parameters: (1) hydrogeological and (2) health-related. Usually, sampling strategies are developed with the goal of reducing uncertainty, but less often they are developed in the context of their impacts on uncertainty. Understanding the impact from each of these components in human health risk can provide guidance for decision makers to best allocate resources towards minimal prediction uncertainty. One of the key points in risk management consists of knowing where to invest characterization efforts in a cost-effective manner. In this talk, a multi-component health risk-based framework is presented which allows decision makers to set priorities through a visualization tool. Results highlight the role of characteristic length-scales characterizing flow and transport in determining data needs within an integrated hydrogeological-health framework. We illustrate conditions where uncertainty reduction in human health risk may benefit from better understanding of the health component as opposed to a more detailed hydrogeological characterization. Through a series of examples, we show how fundamental knowledge on the main physical mechanisms affecting pollutant and solute pathways are necessary to understand the response of complex systems to varying drivers.
Host: Astani CEE Department
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Cassie Cremeans
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Astani Civil and Environmental Engineering Seminar
Tue, May 15, 2012 @ 03:00 PM - 04:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Yujie Ying, Ph.D. Candidate, Department of Civil and Environmental Engineering Carnegie Mellon University
Talk Title: Data-Driven Ultrasonics for Pipe Monitoring
Abstract: Structural Health Monitoring (SHM) is the continuous assessment of structural integrity through permanently installed sensors. SHM complements traditional nondestructive evaluation (NDE) techniques that are time and labor intensive and hence infrequent. SHM allows condition-based structural maintenance to replace the current practice of economically inefficient schedule-based maintenance. However, a major challenge for SHM lies in distinguishing the damage induced changes in the sensed signal from the changes produced by benign environmental and operational variations (such as temperature, air pressure in pipes, fluid flow, etc.).
In this talk, I will present a data-driven methodology for infrastructure monitoring that is robust to ambient environmental variability. I will focus on demonstrating the effectiveness of an integrated machine learning and signal processing approach for damage detection in pipe structures with surface-mounted piezoelectric wafers that generate and sense ultrasonic waves. Ultrasonic waves can propagate long distances with high sensitivity to damage. However, it is difficult to recognize a defect due to the presence of multiple dispersive wave modes and the influence of environmental and operational factors. Laboratory experiments and field tests were conducted on a pipe specimen with randomly-controlled internal air pressure levels, and on an operating hot-water pipe with large and uncontrollable environmental fluctuations, respectively. The sensed ultrasonic data are characterized and mapped onto a high dimensional feature space using various signal processing techniques. Machine learning algorithms are then applied to automatically identify effective features and to detect a weak scatterer on the pipes under complex and highly dynamic operating conditions.
This data-driven monitoring methodology involves an integrated process of sensing, data acquisition, signal analysis, and pattern recognition, for continuous tracking of the structural functionality in an adaptive and cost-effective manner. The techniques developed in this work are expected to have broader applications related to the regular inspection, maintenance, and management of critical infrastructures not limited to pipes.
Host: Astani CEE Department
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Cassie Cremeans
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Astani Civil and Environmental Engineering Seminar
Thu, May 17, 2012 @ 01:00 PM - 02:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Dr. Ketan Savla, Laboratory for Information and Decision Systems, Massachusetts Institute of Technology
Talk Title: Resilient Control for Critical Infrastructure Networks
Abstract: Resilience is becoming a key consideration in the design and operation of critical infrastructure systems such as transportation, production and data networks. Due to their increasing scale and interconnectedness, these systems pose several new challenges. For example, small local disruptions can cascade through the network to cause massive failures, or local actions to mitigate disruptions can increase vulnerability of the other parts of the network. In spite of sustained research efforts, the available approaches either take a static perspective, and hence are inadequate to address these challenges, or they do not provide formal guarantees.
In this talk, I present provably-resilient distributed control policies for dynamic flows over networks, and illustrate the results in the context of urban transportation networks. Specifically, I present a novel class of locally cooperative routing policies. These policies, when used as local adjustments to standard global route choice models, lead to stability of classical transportation equilibria in the dynamical setting. The same policies also render maximum resilience to the network against malicious disruptions. These results rely on a combination of tools from network flows, evolutionary game theory and monotone dynamical systems, and particularly highlight the effect of cascade phenomena on resilience.
Host: Astani CEE Department
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Cassie Cremeans
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Oral Dissertation Defense
Tue, May 22, 2012 @ 02:00 PM - 04:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Kalam Cheung, Environmental Engineering Ph.D. Candidate
Talk Title: Temporal, spatial and toxicological characteristics of coarse particulate matter in an urban area and relation to sources and regulations
Abstract:
To advance our understanding on the relationship between the sources, chemical composition and toxicity of coarse particles, two comprehensive investigations were conducted in the Los Angeles Basin from 2008 to 2010 to characterize the physico-chemical and toxicological properties of ambient coarse particulate matter (CPM). The first study features of a year-long sampling campaign at 10 sampling sites throughout the basin in an attempt to study the spatial and seasonal characteristics of ambient coarse particles. An intensive study, focusing on the diurnal trends, was conducted at 3 sampling sites to examine how the change in meteorological conditions throughout a day may affect the source strength and formation mechanisms of coarse mode aerosols. The results from these two studies have become an invaluable tool to advance our understanding on the cause of the temporal and spatial variation of CPM concentrations and chemical composition, and to identify the linkage between toxicity levels and source-specific chemical constituents in CPM. This investigation thereby provides valuable scientific information for environmental policy decision making, and a strong scientific basis to develop cost-effective strategies to protect the public health from coarse PM exposure.
Advisor: Dr. Costas Sioutas
Location: Kaprielian Hall (KAP) - 345
Audiences: Everyone Is Invited
Contact: Evangeline Reyes