MechSE Seminars
http://illinois.edu/calendar/list/2791
Department of Mechanical Science and EngineeringManipulation and Interrogation of Matter at the Small Scale Enabled by a Controls and Systems Perspective
http://illinois.edu/calendar/detail/2791/33228902
MechSE Seminarhttp://illinois.edu/calendar/detail/2791/33228902Thu, 05 May 2016 12:00:00 CDT<p><strong>Abstract:</strong></p>
<p>The new temporal and spatial regimes of exploration enabled by nanoscience and nanotechnology have led to significant insights into fundamental processes that govern dynamics at the small scale of matter including bio-matter at the molecular scale. These abilities were enabled by breakthroughs in instrumentation that had to overcome fundamental sources of uncertainty such as thermal noise. In this talk, solution methodologies enabled by a modern control approach, in our lab, that have opened new temporal and spatial regimes for investigating matter at the nanoscale will be highlighted. With the exploration of biological processes at the molecular and cellular scale using nano-interrogation tools, it has become evident that evolution has endowed biology with remarkable machinery to perform and achieve precise functionality at the small scale in the presence of a highly uncertain environment. Understanding these bio-molecular systems, apart from providing key insights into biology and the related therapeutic impact, holds the promise for strategies to engineer material and systems at the small scale. Recent efforts in our lab for probing and understanding transport at the molecular scale and key proteins that provide structural integrity will be detailed to illustrate the power of a controls and systems perspectives.</p>
<p><strong>About the Speaker:</strong></p>
<p>Murti V. Salapaka received the B.Tech. degree in Mechanical Engineering from the Indian Institute of Technology, Madras in 1991. He received Masters and doctoral degrees in Mechanical Engineering from the University of California, Santa Barbara, in 1993 and 1997, respectively. From 1997-2007, he was with the Electrical Engineering Department at Iowa State University. From 2007 to 2010, he was an Associate Professor at University of Minnesota, Twin-Cities, where he currently holds the Vincentine Hermes-Luh Chair in Electrical and Computer Engineering. He is currently a Professor and Director of Graduate Studies at the Electrical and Computer Engineering Department at University of Minnesota, Twin-Cities. Prof. Salapaka was the recipient of the 1997 National Science Foundation CAREER Award and the 2001 Iowa State University Young Engineering Faculty Research Award. His research interests are in control and systems theory and its applications to nanotechnology, molecular biology and renewable energy.</p>
<p><strong>Host:</strong> Professor Geir Dullerud</p>MIG Seminar: Large scale tight-binding computations
http://illinois.edu/calendar/detail/2791/33229243
Materials Interest Grouphttp://illinois.edu/calendar/detail/2791/33229243Thu, 05 May 2016 15:00:00 CDT<p><strong>Abstract</strong></p>
<p>Tight-binding or linear combination of atomic orbitals is a method for computing the electronic structure of materials. Like Density Functional Theory (DFT), it depends on the single electron approximation but is significantly less expensive because it includes parameters from DFT, other ab-initio methods, and experiments. In terms of the system sizes usually studied in materials behavior computation, tight-binding bridges the distance and time domains between those typically covered by density functional theory (DFT) and classical molecular dynamics (MD) where the interactions between atoms are given by a pre-determined function and the quantum mechanical nature of electrons is not accounted for. In order to account for the quantum mechanical nature of electrons, the Schrodinger equation has to be solved for the electron wavefunction. The Schrodinger equation is a second order differential equation; one can think of it as a laplacian with an effective potential which itself depends on the charge density, and whose functional form is determined by several approximations. This is the problem solved by DFT, and in the ideal case, a complete continuous orthogonal basis set is used to solve the Schrodinger equation self-consistently. However, the basis set necessarily has to be discrete and finite, and convergence suffers due to the type of basis sets used or the long range of potentials. It is often more convenient to assume a basis set centered around atoms so that we can write the electronic wavefunction of real crystals in terms of atomic orbitals. We may then solve the DFT problem on a small system of atoms with this type of basis set and obtain values of various interactions between orbitals of atoms. These values become parameters that can be used with tight-binding, and have the potential to scale the quantum mechanical treatment of electrons to computations involving hundreds of thousands of atoms. Large matrix systems with an applied load are frequently encountered in engineering applications. In tight-binding, however, we are interested in the entire spectrum (and its eigenvectors) of the Hamiltonian, and the Hamiltonian matrix itself is constantly updated at each iteration. We present two known algorithms, and our variations on it, used to solve for electronic structure of large materials in a self-consistent way. We then present some preliminary results showing how our self-consistent-charge, tight-binding computations scale with problem size and computational resources available.</p>
<p><strong>About the Speaker</strong></p>
<p>Purnima Ghale is a research assistant in Professor Harley Johnson's group in the Department of Mechanical Science and Engineering. She is affiliated with the XPACC (The Center for Exascale Simulation of Plasma-Coupled Combustion) at the University of Illinois, Urbana-Champaign, working on large scale tight-binding simulations and DFT computations of properties of the silica electrode surface. Additional computational resources from (i) the Illinois Campus Computing Cluster and (ii) Bodony Group Computer cluster are gratefully acknowledged. This work was supported by XPACC (Department of Energy, National Nuclear Security Administration, Award Number DE-NA0002374).</p>
<p><strong>Host:</strong> Professor Elif Ertekin</p>Fluid Mechanics Seminar: Ignition and Extinction in Condensed Phase Combustion
http://illinois.edu/calendar/detail/2791/33077568
Fluid Mechanics Seminarhttp://illinois.edu/calendar/detail/2791/33077568Fri, 13 May 2016 12:00:00 CDT<p><strong>Host:</strong> Professor Scott Stewart</p>DIG Seminar: Dynamics of Localized Structures in Dissipative Nonlinear Lattices
http://illinois.edu/calendar/detail/2791/33227769
Dynamics Interest Seminarhttp://illinois.edu/calendar/detail/2791/33227769Fri, 13 May 2016 15:00:00 CDT<p><strong>Abstract</strong></p>
<p>This talk reviews results about the existence of spatially localized waves in nonlinear chains of coupled oscillators, and provides new results for the Klein-Gordon (KG) lattice and model of a one-dimensional magnetic metamaterial formed by a discrete array of nonlinear resonators. Localized solutions include solitary waves of permanent form and traveling breathers which appear time periodic in a system of reference moving at constant velocity. For KG lattices of magnetic metamaterials, we obtain a general criterion for spectral stability of multi-site breathers for a small coupling constant. For the metamaterial lattices we focus on periodic traveling wave due to the presence of periodic force. We employ topological and variational methods to study the existence and the stability of periodic waves. These localized structures are also computed and discussed numerically. We consider the dynamics of a pair of parametrically-driven coupled superconducting quantum interference device (SQUIDs) arranged in series. This system exhibits rich nonlinear behavior, including chaotic effects.</p>
<p><strong>About the Speaker</strong></p>
<p>Dr. Vassilis Rothos is currently an Associate Professor in the School of Mechanical Engineering and member of Lab of Nonlinear Mathematics at the Aristotle University of Thessaloniki. He is a member of Complex System Group at Institute of Applied & Computational Mathematics at FORTH Heraklion Crete, Greece. He received his PhD from the University of Patras in 1999 under the supervision of Prof. Tassos Bountis. His research focuses on applied dynamical systems, nonlinear waves in PDEs and Lattices and applied analysis.</p>
<p><strong>Host:</strong> Professors Larry Bergman and Alex Vakakis</p>