Conferences, Lectures, & Seminars
Events for October
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Ph.D. Oral Defense Dissertation
Wed, Oct 03, 2012 @ 02:00 AM - 04:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Roshanak Varjavand, CE Ph.D. Candidate
Talk Title: TBA
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani CEE Ph.D. Seminar
Fri, Oct 05, 2012 @ 03:00 PM - 05:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Falk Feddersen Associate Research Oceanographer , Integrative Oceanography Division Scripps Institution of Oceanography, UCSD
Talk Title: Surfzone eddies in strong alongshore currents: Forced or Instabilities?
Abstract:
Beaches throughout the United States are chronically impacted by poor water quality, making swimmers sick and affecting coastal economies. Run-off pollution often drains directly into the surfzone and the mechanisms dispersing and diluting pollution or other tracers (e.g. larvae) are not clear. Surfzone 2D turbulent eddies are the dominant mechanisms for surfzone dispersion and dilution, and these eddies are generated either from a shear-instability of the alongshore current (âshear-waves''), from finite-crest length breaking of individual waves, or from alongshore gradients in wave-group forcing, which have distinct length-scales. SandyDuck based observations of surfzone eddies are compared to funwaveC model simulations. Finite-crest length breaking induces energy at much larger frequencies and wave-lengths than a NSWE model. The relative contributions of shear instabilities and finite-crest length breaking on the momentum and vorticity dynamics are examined. The results will have implications for modeling the dispersion and dilution of surfzone tracers (whether fecal indicator bacteria, sediment, or larvae).
Host: Dr. Patrick Lynett
Location: John Stauffer Science Lecture Hall (SLH) - 102
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani CEE Ph.D. Seminar
Fri, Oct 12, 2012 @ 03:00 PM - 05:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Charles DeVore, CE Graduate Student
Talk Title: Experimental Verification of Substructure Identification for Damage Detection
Abstract:
Damage detection for civil structures is limited by several factors including, among others, poor signal to noise ratios, a large number of unknown parameters and a limited set of measured responses. Global structural health monitoring (SHM) techniques that track modal parameters often fail to detect damage because they remain insensitive to common forms of structural damage. Moreover, a high-dimensional search space of identified parameters makes global inverse problems ill-conditioned. To overcome some of these limitations, many researchers have advanced substructure identification as a methodology to directly detect local stiffness changes using the local neighborhood of measured responses, thereby improving damage detection and SHM scalability in civil structures.
Building on substructure identification methods previously developed by Zhang and Johnson (2011), this paper develops a substructure identification estimator that identifies the story stiffness and damping parameters of a four-story shear building. Concurrent with the estimator derivation, identified parameter confidence intervals are developed; identification performance is predicted through a first-order error analysis. Using the proposed estimator, experimental testing is performed on a 12 ft four-story steel structure subject to base excitation. The floors of the structure are steel masses and the columns are bolted threaded rods. While additional threaded rods can be added/removed to change the story stiffness, these tests examined several configurations in which small stiffness changes are induced by loosening floor-level connections. These changes simulate damage and are successfully detected by substructure identification within computed confidence intervals. The substructure identified parameters are compared against global modal measures and found to be more sensitive to damage. Furthermore, the estimator's performance follows predictions from the error analysis and motivates future work with identification assisted by structural control.
Location: John Stauffer Science Lecture Hall (SLH) - 102
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani CEE Department Ph.D. Seminar
Fri, Oct 19, 2012 @ 03:00 PM - 05:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Dr. David Dzombak, Walter J. Blenko, Sr. University Professor, Civil and Environmental Engineering , Carnegie Mellon University
Talk Title: The Need and Challenge of Alternative Water Sources for Use in Electric Power Production
Abstract: Thermoelectric power generation accounts for as much freshwater withdrawal as agricultural irrigation in the U.S., with both at about 40% of total. Meeting the future cooling water demands for electric power production will be difficult in locations with limited freshwater resources, and is already prompting interest in the use of waters of impaired quality, such as treated wastewater, mine drainage and industrial process wastewater, as alternative sources. This talk will provide an overview of the water-energy challenge facing the U.S. and will examine the need for and challenges of using alternatives to freshwater for power plant cooling.
Host: Prof. Lucio Soibelman
Location: John Stauffer Science Lecture Hall (SLH) - 102
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani CEE Oral Dissertation Defense
Tue, Oct 23, 2012 @ 02:00 PM - 04:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Roshanak Varjavand, CE Ph.D. Candidate
Talk Title: Numerical Simulation of Seismic Site Amplification Effects
Abstract:
The concept of substructure deletion proposed for the analysis of a rigid foundation was adapted for the analysis of site amplification effects in alluvial valleys. A major modification was made for the present application such that the boundary integration equation method was used for both the finite size interior problem and semi-infinite exterior wave radiation problem. The modification was made to reduce the possible incompatibility between the finite element method, a volume formulation, and the boundary integral equation method, a surface formulation. The substructure deletion concept allows simple, century-old, basic Green's Functions to be used to produce excellent wave scattering results for topographical irregularities as well arbitrarily shaped alluvial valleys overlying stiffer bedrock. The concept is applicable to three-dimensional geometries as well as two-dimensional problems. Results are given for incident SH, P, SV and Rayleigh waves.
Advisor: Professor Hung Leung Wong
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani CEE Oral Dissertation Defense
Wed, Oct 24, 2012 @ 11:00 AM - 01:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Hyoung-Jin Kim, Ph.D. Civil Engineering Candidate
Talk Title: Numerical and Experimental Study on Dynamics of Unsteady Pipe Flow Involving Backflow Prevention Assembly
Abstract:
When control valves at the end of pipeline close simultaneously, two pressure waves are generated at each end and propagating toward to the other end. Those waves continue to go back and forth along pipelines until they are damped out to next steady states. This study provides information on the computer simulation of a rapid transient event called water hammer. The energy loss term due to friction in the unsteady model consists of quasi-steady contribution and unsteady contribution. For the present model, an equivalent friction coefficient is used to replace the quasi-steady friction coefficient, inclusive minor energy loss factors. The unsteady component has been related to the combination of the instant acceleration and instant convective acceleration. The numerical results of the present model are compared with the experimental records. The computer results based on the unsteady friction 1D model was successful to follow general trends of water hammer phenomena, corresponding with sudden changes in flow. This study later extends to the dynamic characteristics of backflow prevention assemblies under rapid transient condition. A numerical program for rapid transient pipe flow interconnected with a backflow prevention assembly has been developed using a coupling model and numerically solved by the method of characteristics.
Advisor: Professor Jiin Jen Lee
Location: Kaprielian Hall (KAP) - 335
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
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Astani CEE Ph.D. Seminar
Fri, Oct 26, 2012 @ 03:00 PM - 05:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Ryan Thatcher, ENE Ph.d. Candidate
Talk Title: Integrated Electrokinetic and Microbial Fuel Cell Technologies for Enhanced Transport and Bioremediation of Hexavalent Chromium in Groundwater
Abstract:
Groundwater contamination threatens potable water supplies around the world, and this fact has encouraged the progression of novel research for groundwater treatment. Hexavalent chromium (CrVI) is an EPA priority contaminant due to its high toxicity, and its prevalence in groundwater around the world as a result of improper disposal practices from a variety of industries. CrVI is highly mobile in water systems due to its solubility, making treatment by conventional methods difficult and costly.
Electrokinetic remediation is a technique that can be used for transporting ionic contaminants, including CrVI (as HCrO4-) by the application of an electric potential across a contaminated aquifer. Electrokinetic remediation is often limited by a pH change due to electrolysis reactions. These reactions create OH- at the cathode and H+ at the anode, which migrate towards the opposite electrodes by electrokinetic phenomena. At the point of intersection of these fronts a significant drop in electrical conductivity occurs, causing transport to slow or stop completely. Additionally, the dynamic pH change affects precipitation and dissolution reactions, which govern the solution chemistry and availability of the contaminant for transport. Many enhancement techniques have been investigated to mitigate this problem, however they can add significant economic and environmental cost.
This study investigates the potential to enhance electrokinetic transport of CrVI in groundwater while also promoting its reduction to CrIII by integrating an electrokinetic system with microbial fuel cell (MFC) technology. Recent studies have shown MFCs to be effective in CrVI reduction, as CrVI can act as an electron acceptor when introduced to the MFC cathode compartment. This reaction is catalyzed by the presence of biofilm on the cathode, which facilitates a complex electron transport system from the cathode to CrVI in solution. In this context, Shewanella putrefaciens MR-1 bacteria have been documented to be effective biocatalysts for this application, and different carbon sources including lactate, acetate, formate, and pyruvate have demonstrated to be effective electron donors in the anode compartment.
In this study, the integration of these technologies is evaluated using a soil column under an applied electric potential, and an MFC with anode and cathode reservoirs with a 300 mL capacity. The electric potential applied across the soil column is varied in different experiments from 0.5 â 2.0 V/cm in an effort to optimize transport by counteracting the advective pull of CrVI towards the cathode by water flow. The soil column is operated with a continuous flow of simulated groundwater spiked with CrVI at a rate comparable to that of groundwater in sandy soils. The flow direction is from the anode towards the cathode, while CrVI is transported by electrokinetic phenomena in the opposite direction. During operation, the soil column effluent adjacent to the anode reservoir is pumped out into the cathode of the MFC. Recirculating solution to and from this location in the column will mitigate the dramatic drop in pH, which occurs in the absence of enhancement strategies from H+ generation at the anode. Effluent from the cathode reservoir of the soil column is sampled and analyzed for CrVI by ion-exchange chromatography to determine the extent of treatment.
The optimization of the electrokinetic and MFC integration will be discussed in this presentation. Key points of discussion will be CrVI reduction rates and mechanisms at the biocathode, cathode effluent CrVI concentrations, effects of solution circulation to enhance CrVI transport, and energy production by the MFC.
Location: John Stauffer Science Lecture Hall (SLH) - 102
Audiences: Everyone Is Invited
Contact: Evangeline Reyes