Conferences, Lectures, & Seminars
Events for November
-
Nanocomposites for Distributed Structural Monitoring and Damage Detection
Thu, Nov 05, 2009 @ 02:00 PM - 03:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Dr. Kenneth J. Loh,
Assistant Professor, University of California, Davis, Department of Civil & Environmental Engineering, One Shields Avenue, 2001 Engineering III, Davis, CA 95616, USA Abstract: Structural deterioration, excessive loading, impact damage, and corrosion have been identified as critical and long-term problems that constantly threaten the integrity and reliability of structural systems (e.g., civil infrastructures, aircrafts, and naval vessels). In particular, the field of structural health monitoring (SHM) and damage detection provides quantitative global- and component-scale structural response data for monitoring the performance of these structures; however, most sensors are subjected to performance limitations (e.g., sensitivity, dynamic range, bandwidth, and form factor) and only offer measurement of structural behavior at discrete locations. In this regard, nanotechnology offers a plethora of nanomaterial fabrication techniques for the design of next-generation multifunctional nanostructured systems to solve complex engineering problems. Multifunctional systems are defined to possess a diverse suite of engineering functionalities including self-sensing, actuation, self-healing, power harvesting, among many others. Here, carbon nanotubes are employed and encoded with a variety of electrochemical and electromechanical sensing transduction mechanisms for structural health monitoring and damage identification. First, using a layer-by-layer nanocomposite assembly technique, the films' electrical properties change linearly in response to applied external stimuli (e.g., tensile-compressive cyclic loading and pH). When coupled with radio frequency identification (RFID) technologies, a low cost and high performance passive wireless sensor is fabricated for densely-distributed SHM. Laboratory validation studies demonstrate that these sensors can measure strain and pH/corrosion at its instrumented locations, but damage localization requires interpolation between sensors. Alternatively, the proposed carbon nanotube-based films are paired with an electrical impedance tomographic conductivity image reconstruction algorithm. Specifically, the nanocomposite "sensing skins" are validated for spatial strain, pH, corrosion, and impact damage sensing and is shown to be capable of accurately identifying damage (i.e., strain, impact, and corrosion) location and magnitude. Biography Dr. Kenneth J. Loh is an Assistant Professor in the Department of Civil & Environmental Engineering at the University of California, Davis. He received his B.S. degree in Civil Engineering from Johns Hopkins University in 2004. He continued his graduate studies at the University of Michigan where he completed his M.S. degree in Civil Engineering in 2005, a second M.S. degree in Materials Science & Engineering in 2008, and a Ph.D. degree in Civil Engineering in 2008. His research interests include the development of multifunctional nanocomposites, biologically-inspired materials for sensing, actuation, and power harvesting applications, and wireless sensing.
Location: Kaprielian Hall (KAP) - rielian Hall 209- On Webex. Please call department for more infomation
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
-
Two Applications of Computational Electromagnetics: ...
Wed, Nov 11, 2009 @ 02:00 PM - 03:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
...Moving Objects with the Force of Light and Improving Solar Cell Performance. Speaker: Dr. Michelle L. Povinelli, Ming Hsieh Department of Electrical Engineering, University of Southern California Abstract: In the first part of the talk, I will discuss how light can be used to move and reposition microscale objects. Our work has demonstrated novel applications of optical forces within integrated microphotonic devices-a type of "optical circuits" that use light rather than electrons to carry information. I will present designs for devices that rotate the polarization of light by taking advantage of light forces. In the second part of the talk, I will discuss how computational electromagnetic modeling can be used to design higher-efficiency solar cells. We calculate the optical absorption of vertically aligned silicon nanowire arrays. We optimize the ultimate efficiency of the solar cell with respect to filling ratio and lattice constant. We identify two enhancement mechanisms, an increase in field concentration within the nanowire and the excitation of guided resonance modes. Our results show that an optimized silicon nanowire array can have higher efficiency that a solid thin film. Michelle Povinelli is an Assistant Professor of Electrical Engineering and holder of the WiSE Jr. Gabilan Chair at the University of Southern California. She is a recipient of a NSF CAREER Award and an Army Young Investigator Award. She received a BA from the University of Chicago, an MPhil from the University of Cambridge, where she studied as a Churchill Scholar, and a PhD from the Massachusetts Institute of Technology, all in Physics. She completed postdoctoral research in the Electrical Engineering Department at Stanford University and was selected as one of five national recipients of a L'Oreal For Women in Science Postdoctoral Fellowship. She has co-authored over twenty-five refereed journal articles and holds two US Patents.
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
-
AB 32 Scoping Plan Implementation
Fri, Nov 20, 2009 @ 01:00 PM - 02:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Speaker: Hung-Li (Robert) Chang, Ph.D., California Environmental Protection Agency, Air Resources Board, Mobile Source Control Division, Emission Research and Regulatory Development BranchAbsract:
On September 27, 2006, Governor Schwarzenegger signed Assembly Bill 32, the Global Warming Solutions Act of 2006 (Núñez, Chapter 488, Statutes of 2006). The event marked a watershed moment in California's history. By requiring in law a reduction of greenhouse gas (GHG) emissions to 1990 levels by 2020, California set the stage for its transition to a sustainable, clean energy future. This historic step also helped put climate change on the national agenda, and has spurred action by many other states. The California Air Resources Board (ARB or Board) is the lead agency for implementing AB 32, which set the major milestones for establishing the program. ARB met the first
milestones in 2007: developing a list of discrete early actions to begin reducing greenhouse gas emissions, assembling an inventory of historic emissions, establishing greenhouse gas emission reporting requirements, and setting the 2020 emissions limit.The Assembly Bill 32 Scoping Plan contains the main strategies California will use to reduce the greenhouse gases (GHG) that cause climate change. The scoping plan has a range of GHG reduction actions which include direct regulations, alternative compliance mechanisms, monetary and non-monetary incentives, voluntary actions, market-based mechanisms such as a cap-and-trade system, and an AB 32 cost of implementation fee regulation to fund the program. The proposed scoping plan was released on October 15, 2008 and approved at the Board hearing on December 12, 2008.
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes
-
Modeling of Multi-Scale Continuum-Atomistic System Using Homogenization Theory
Wed, Nov 25, 2009 @ 01:00 PM - 03:00 PM
Sonny Astani Department of Civil and Environmental Engineering
Conferences, Lectures, & Seminars
Oral Defense by: Karthikeyan Chockalingam, Ph.D. Candidate, USC, Astani Department of Civil and Environmental EngineeringThe main objective of the dissertation is to develop multi-scale algorithms for continuum-atomistic problems. The focus is on sequential multi-scale simulations. In sequential multi-scale methods, the computations at the various scales are, in a sense, decoupled. This means, for example, that, for a continuum/atomistic simulation, large scale macroscopic continuum calculations rely on the results of fine scale computations and information obtained on an atomistic cell. While the procedures developed in this thesis could be used in conjunction with a number of sequential multi-scale methods, the focus here is on the homogenization technique. As has been the case in traditional finite element applications of homogenization, one of the principal focuses in this thesis will be on the computation of macro scale constitutive parameters; but, in this case, these constitutive representations come from the atomistic calculations.The thesis has four parts that develop various aspects of the theme of the work. The dissertation focuses on the following applications:1. Problems involving mechanical loading of solids and structures under static load at zero temperature.The focus is on creating multi-scale continuum/atomistic simulation methods which use the atomistic model to provide an improved material representation including the effects of material defects. This topic could be useful in modeling fracture and failure.2. Computation of thermo-mechanical constitutive parameters at finite temperature conditions.This procedure focuses on using the atomistic scale calculation to define constitutive parameters. It assumes that equilibrium conditions exist at the atomistic scale. It does not attempt to track, in a time history sense, the dynamics at the atomistic scale. It does require the solution of an atomistic free vibration problem with natural frequencies dependent on temperature. The procedure defines macroscopic thermo-mechanical constitutive parameters, like the specific heat and the coefficient of thermal expansion, as a function of temperature. These properties could be used directly in a macroscopic continuum finite element model which would be valid at the full range of temperatures.3. Dynamic problems involving the simulation of the thermo-mechanical behavior of systems at finite temperature, with and without heat transfer.This procedure focuses on using the atomistic scale calculation to define multi-scale, thermo-mechanical momentum and energy equations. It does attempt to track, in a time history sense, the dynamics at the atomistic scale. Energy equations are derived for both the scales based on first law of thermo-dynamics. Two types of application problems are used to demonstrate the theory. The first involves thermal stress analysis simulation in which the temperature has no time variability and, thus, no heat transfer occurs. The second involves simulations with time varying temperatures and include heat transfer effects. 4. Implicit time integrations algorithms for atomistic momentum equations that can be seamlessly coupled to macro models.
Location: Kaprielian Hall (KAP) - 209
Audiences: Everyone Is Invited
Contact: Evangeline Reyes