Graduate Student Seminar Scheduled for November 30th

The Fall 2011 Beckman Institute Graduate Student Seminar Series continues on Wednesday, November 30th. The seminar will feature three short talks from students Amanda Jones, Tan Nguyen, and Johan Strumpfer. The seminar will be held in Beckman Institute Room 1005 and a pizza lunch will be served to those attending the talks.

The Beckman Institute Graduate Student Seminar Series presents the work of outstanding graduate students working in Beckman research groups. The seminars begin at Noon in Beckman Institute Room 1005 and are open to the public. Lunch will be served.

Recovery of Fiber/Matrix Interfacial Bond Strength Using a Microencapsulated Solvent-Based Healing System
Amanda Jones

Optical MicrographsFigure 1: Optical micrographs of (a) a microbond sample functionalized with resin-solvent filled capsules, and (b) a control microbond sample with a plain fiber. (c) SEM image of a functionalized fiber with resin-solvent filled microcapsules.

Full recovery of interfacial bond strength after complete fiber-matrix debonding is achieved with a microencapsulated solvent based healing chemistry.  The surface of a glass fiber is functionalized with microcapsules (ca. 1 μm diameter) filled with varying concentrations of reactive epoxy resin and ethyl phenylacetate (EPA) solvent.   Microbond specimens consisting of a single fiber and a microdroplet of epoxy are tested, and the interfacial shear strength (IFSS) during the initial (virgin) debonding and subsequent healing events are measured.  Debonding of the fiber-matrix interface ruptures the capsules, releasing resin and solvent into the crack plane.  The solvent swells the matrix, initiating transport of residual amine functionality for further curing with the epoxy resin deposited in the crack plane.  Using a resin solvent ratio of 97:3, we achieve a maximum of 100% IFSS recovery– a significant enhancement over prior work that reported 44% average recovery of IFSS with microencapsulated DCPD monomer and Grubbs catalyst healing agents.  Since microcracking and debonding of the fiber-matrix interface is one of the key failure mechanisms in composite materials, healing this damage has potential to increase composite lifetime by preventing catastrophic growth of smaller flaws

Biography:  Amanda Jones graduated with a mechanical engineering bachelors from University of Tulsa in Oklahoma.  She is currently a 3rd year graduate student in the Theoretical and Applied Mechanics Department and works in the Autonomous Material Systems group with Prof. Nancy Sottos and Prof. Scott White.  She specializes in self- healing composite materials.

A Framework for Denoising and Deblurring Fourier Transform infrared Spectroscopic Images
Tan Nguyen

Fourier Transform-Infrared (FT-IR) Spectroscopic Imaging  is a valuable tool for obtaining chemical information from tissue samples and has the potential to greatly assist pathology, including cancer diagnosis. However, current limitations of FT-IR imaging include long acquisition time, vast data storage, low signal-to-noise ratio (SNR), and low spatial resolution due to contaminated noise, pixelation and optical effects such as optical diffraction and Mie scattering. In this talk, I will present a systematic framework to denoise and deblur spectroscopic images by exploiting the data's low-rank property, optical diffraction modelling, and Variational Bayesian deconvolution. Using this framework, clear images at higher resolutions can be obtained from original noisy and diffracted ones.

Biography:  He received his undergraduate degree in Automation from the University of Technology, Vietnam in 2009 in the honor program. Since 2011, he has studied in the Department of Electrical and Computer Engineering at the University of Illinois at Urbana-Champaign. Currently, he is working in the IFP & CISL group under the supervision of Prof. Minh N. Do and Prof. Rohit Bhargava. His research interests include signal processing and compressive sensing for IR-spectroscopic imaging. Tan received the University Gold Medal from Hochiminh University of Technology in 2009 for highest graduation ranking, graduate research award from SORUN KITAGAWA in 2009 and from TOSHIBA in 2009, 2010.

How Quantum Coherence Assists Bacterial Light Harvesting
Johan Strumpfer

Purple photosynthetic bacteria live in low-light environments and thus need to capture and process every photon that they can to survive. This need has optimized their light harvesting efficiency to near unity. Their remarkable efficiency is achieved by densely packing in many pigment molecules, which capture photons, and exploiting quantum mechanics, particularly the coherent sharing of excitation, to transport absorbed photon energy over long distances in a short time.