2011 Seminar Archive


Spring, 2011

Programming Molecular Networks

Elisa Franco

Graduate Student
Department of Control and Dynamical Systems
California Institute of Technology
Pasadena, CA

How do living organisms process information and implement their responses to external stimuli? Even in the simplest cells, sensing, computation and actuation are structurally embedded in the biochemistry of complex molecular networks, and we need to develop new paradigms to explain and engineer such structures. Quoting Richard Feynman, what we cannot create, we do not understand: by programming and building simple molecular networks from the bottom-up, scientists have an opportunity to gain insight into the design principles of more complicated, naturally occurring circuits.

In this talk, I will describe how DNA and RNA can be used as simple building blocks to construct molecular circuits encoding complex functionalities, because their interactions can be predicted and specified with high confidence. In particular, we have used nucleic acids to investigate two challenges: synchronization and scalability of biochemical networks. I will describe how the activity of two synthetic genes can be matched, by using their outputs to create positive or negative feedback loops. Scaling up our perspective, to synchronize the operations of a larger number of circuits we may need “timing” devices: for instance, digital clock generators coordinate the state transitions of millions of silicon circuits. I will describe how a tunable synthetic oscillator can be used to time the conformation of a DNA nano-mechanical device called “DNA tweezers,” evaluating several modes of connection. Because the biochemical interconnections are created by stoichiometric binding of our oscillator components and its “load” components, we observed a remarkable deterioration of the oscillator behavior as we increased its load concentration. To reduce this undesired retroactivity we engineered an “insulator circuit”, the molecular equivalent of an operational amplifier, which improves the modularity and scalability of the system. To our knowledge, this is the first experimental attempt to use a synthetic biochemical oscillator to drive several types of downstream processes, in a plug-and-play fashion.

Elisa Franco is currently a graduate student at the California Institute of Technology, in the Department of Control and Dynamical Systems. She got her Laurea degree in Power Systems Engineering from the University of Trieste, Italy, where she also earned a PhD in Automatic Control. Her current research interests are in the field of synthetic and systems biology.

Wednesday, January 12, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Engineering the Human Eye

Alfredo Sadun

Professor
University of Southern California
Los Angeles, CA

The human eye reflects elements of design that represent an interesting tension between the rules of evolution (you need a path between steps and each step must at least not have a negative value added) and all sorts of tradeoffs between benefits that would have selection value. We will look at this process by asking how we might design such a system taking the following steps.

  1. How big should it be?
    1. Too small and you have <1.2mm aperture limit of diffraction
    2. Too large and it’s neurologically (and metabolically) expensive
  2. Do you grow it after birth (axial length changes require new focal lengths)?
  3. How many pixels (separation of less than 30 seconds of arc = diffraction gratings)?
  4. Scotopic vs Photopic (predator or prey)?
  5. Transient or sustained (integrating over space or time)?
  6. Duality approach of M & P cells (How is the hawk eye superior?)
  7. Color vs B&W
  8. How many color cones do we want (predator vs prey)?
  9. Did you forget the heat sink?
  10. Super-sustained RGCs (melanopsin) for
    1. Pupils
    2. Circadian rhythms

How do you get there from here: 10 step plan notwithstanding that evolution doesn’t have a trajectory.

  1. Discriminating light vs dark = photopigment on a membrane (phototaxis and circadian rhythm)
  2. Direction of light (light wall or just a cup)
  3. Focus for better resolution (almost close the cup for pinhole aperture)
  4. Maintain transparency (close with cornea, use aqueous and vitreous and IOP for sphere).
  5. Movable iris to increase light
  6. Lens to focus when pupil is not a pinhole
  7. Deal with optic nerve that leaves the eye and makes a big blind spot (how do you keep the pressure in when you have an exit?).
  8. Put psychophysical filters into the eye to decrease data and limit optic nerve head size by using Bipolars, Horizontals, Amacrine). Edges matter more than filler.
  9. Fovea and eye movements
  10. M & P cell parallel processing
Wednesday, January 19, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

The Role of Thermochemistry in Hypersonic Shear Flows

Joanna M. Austin

Assistant Professor
Department of Aerospace Engineering
College of Engineering
University of Illinois at Urbana-Champaign, IL

In high enthalpy hypersonic flight, thermochemical relaxation times are typically comparable to flow residence times, leading to nonlinear coupling between chemical reactions, vibrational excitation, and fluid mechanics. The chemical species and internal energy of the gas depart significantly from equilibrium. Experimental data in hypervelocity flows are scarce, partly because creating high enthalpy conditions in ground test facilities is extremely challenging and flight tests are expensive.

A new expansion tube facility capable of test gas Mach numbers from 3.0 to 7.4 has been built at Illinois and carefully characterized with experimental measurements and numerical simulations. Two canonical shear flows are being examined in the high enthalpy free stream: triple-point generated free shear layers and boundary layers flows. Initial experiments identified an opposing wedge configuration used to generate a Mach reflection with associated triple-point shear layers. The experimental configuration is chosen to give well-characterized inflow and boundary conditions. In addition, a Mach reflection results in a shear layer that separates a gas stream that has passed through a normal shock from a gas stream that has passed through two oblique shocks, leading to dramatically different temperatures and degree of dissociation across the shear layer. Key diagnostic tools include spectroscopic measurements confirming the presence of dissociated NO behind the Mach reflection, flow visualizations, and temperature measurements benchmarked against calculations using detailed and reduced chemical kinetic mechanisms.

The experimental work is complemented by spatial linear stability analysis. This study is the first linear stability analysis of a hypersonic shear layer to include detailed modeling of molecular effects. An existing molecular-molecular energy transfer rate model is extended to higher collisional energies. Non-equilibrium model results are compared with calculations assuming equilibrium and frozen flow over a range of (frozen) convective Mach numbers from 0.341 to 1.707. Non-equilibrium effects appear in the creation of nitrous oxide due to dissociation. Dissociation and vibration transfer effects on the perturbation evolution remain closely correlated at all convective Mach numbers.

Joanna Austin is an Assistant Professor in the Aerospace Engineering Department at the University of Illinois at Urbana-Champaign. She received B.E. (Mechanical and Space Engineering) and B.Sc. (Mathematics) degrees from the University of Queensland, Australia in 1996 and 1997, and M.S. and Ph.D. degrees from GALCIT at the California Institute of Technology in 1998 and 2003. She directs the Compressible Fluid Mechanics Laboratory at Illinois, where her research interests include hypervelocity flows, bubble collapse under dynamic loading, detonation, compressible geological flows, and experimental fluid mechanics. Honors and awards include the Richard Bruce Chapman award for distinguished research in hydrodynamics in the Engineering and Applied Sciences Division at Caltech, 2003, the Young Investigator Award from the Air Force Office of Scientific Research, 2007, and the National Science Foundation CAREER award in 2010.

Wednesday, January 26, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Humans Beyond Low Earth Orbits: Challenges and Opportunities in Astrodynamics

B. Villac

Professor
University of California, Irvine
Irvine, CA

The NASA plan for sending humans beyond low-Earth orbits in a sustainable manner poses many challenges (at all levels: technical, political,…), as well as a plethora of opportunities. This talk explores a few of the technical challenges and opportunities in the realm of spaceflight dynamics.

Firstly, sustained exploration implies a need for space-based infrastructure, notably for navigation and communication systems. This leads us to a discussion on constellation optimization in multi-body environments, and the associated variational problems. We show that the use of dynamical system theory and the analysis of periodic orbit families allows us to reduce this problem to a one-dimensional optimization over a graph. These results are applied to the concept of autonomous navigation constellation. The notion of family –i.e., continuous set of orbit– is then extended to transfer problems, demonstrating some limitations of classic design methodologies and possible techniques to go around these.

Secondly, humans in space also implies safety issues. This is notably amplified with the current vision of sending humans to asteroids, where the dynamics present short time scales and is generally poorly characterized before encounter. Here the questions addressed are the techniques to ensure mission recovery –or at least avoiding critical events such as impacts or uncontrolled escape when orbiting a small body– in the face of potential engine failure. The analysis of the resulting optimal control problems and orbital stability issues leads to new transfer and mission concepts and the challenging problem of orbital motion characterization under large parameter uncertainties.

Finally, a few astronauts in space means a large team of qualified engineers on the ground, planning, designing, preparing, operating, supporting the missions ans the astronauts. All this, starts with education and the formation of good engineers. The last part of the talk will briefly discuss the cubesat project pursued at UCI in order to answer this need.

Prof. Villac is currently assistant professor at the University of California, Irvine (UCI). Prior to joining UCI in 2006, Prof. Villac worked at the Jet Propulsion Laboratory and the California Institute of Technology, developing novel low-thrust trajectory analysis and design methods for the Jupiter Icy Moon Orbiter mission. He received his Ph.D in aerospace engineering in 2003 from the University of Michigan, Ann Arbor. His research is focused on astrodynamics, exploring the applications of modern dynamical system theory to the analysis and development of new space mission concepts. He is also advising the UCISAT project which is currently preparing to launch its first cubesat.

Wednesday, February 2, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

An Introduction to Industrial Rotor Dynamics

Louis Komzsik

Chief Numerical Analyst
Office of Architecture and Technology
Siemens PLM Software
10824 Hope Street
Cypress, CA, 90630, USA

The rotational phenomenon is instrumental in our everyday lives. The effects of the phenomenon range from the well known centrifugal force, through the Coriolis forces and to the Euler force. The modeling and computation of such forces forms the basis of rotor dynamics. Rotor dynamics of elastic structures is a very important topic of the energy (turbines and windmills) and transportation (helicopter and airplane propellers) industry. The talk will briefly review the physical fundamentals of rotating phenomenon and its computational formulation with finite elements. It will also present a demonstration example and an industrial case study from NASTRAN, the world leader in commercial finite element analysis. It is aimed at undergraduate and graduate engineering or computational science students, but well suited for interested faculty as well.

Dr. Louis Komzsik, Chief Numerical Analyst of Siemens Industry Division, PLMS. He is a graduate of the Technical University of Budapest in Hungary and worked for almost four decades in the industry, the last three in the United States. His work focuses on developing computational techniques for industrial applications in commercial finite element analysis. Dr. Komzsik is the author of several books; one on them on Lanczos method published by SIAM has also been published in Japanese, Hungarian and Chinese. His book, Computational Techniques of Finite Element Analysis, is in its second edition and used by engineers worldwide. His Approximation Techniques for Engineers and Applied Calculus of Variations for Engineers are used at several universities in the US and in Europe.

Wednesday, February 9, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

From Gliding Ants to Andean Hummingbirds and Giant Dragonflies: The Origins and Evolution of Animal Flight

Robert Dudley

Professor
University of California at Berkeley
Berkeley, CA

Unsteady aerodynamic mechanisms underpinning animal flight have recently been intensively studied, but less well understood are those evolutionary pathways leading to the acquisition and subsequent elaboration of flapping flight. Recently discovered behaviors in Neotropical canopy ants demonstrate directed aerial descent in the complete absence of wings; controlled aerial behavior appears to have preceded the origin of wings in insects and other flying animals. Variation in atmospheric composition during the late Paleozoic may have influenced the initial evolution and subsequent diversification of insects, as well as the widespread phenomenon of arthropod gigantism, including but not limited to dragonflies with a 70 centimeter wingspan. For fully flighted forms, judicious use of helium to create physically variable gas mixtures permits decoupling of physiological from aerodynamic constraints on hovering performance. Such constraints are revealed in natural contexts through the study of hummingbird and bumblebee flight capacity across steep altitudinal transects.

Wednesday, February 16, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Advances in Computer Simulations of Turbulent Combustion

Stephen B. Pope

Sibley College Professor
Sibley School of Mechanical & Aerospace Engineering,
Cornell University
Ithaca, New York 14853

Combustion will remain a key technology for several decades in power generation, transportation and many other applications. Advances are continually sought in terms of efficiency gains, pollution reduction, and alternative technologies facilitating carbon capture. As in other areas of engineering, computer simulations are central to the design and development of combustion technologies. Great strides are being made both in the computation fluid dynamics (CFD) of turbulent reactive flows and in the development of more accurate and comprehensive chemical mechanisms, which may involve thousands of species. However, the combination of advanced approaches to turbulent flows and large chemical mechanisms poses a formidable computational challenge. The approach to the simulation of turbulent combustion described in this talk consists of the following three components: large-eddy simulation (LES) to treat the flow and turbulence; a probability density function (PDF) method to treat the turbulence-chemistry interactions; and, dimension-reduction and tabulation for the computationally-efficient implementation of combustion chemistry. Recent advances and examples of simulations are presented.

Wednesday, February 23, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Therapeutic Ultrasound Applications in the Human Brain – From Noninvasive Surgery to Local Drug Delivery

Thilo Hoelscher

Professor
and
Director Brain Ultrasound Research Laboratory

Departments of Radiology and Neuroscience
University of California, San Diego
San Diego, CA

Despite its initial purpose of being a purely diagnostic tool the knowledge of ultrasound induced biomechanisms increased rapidly during the last years, changing significantly the scope of how ultrasound might be used in the future. Noninvasive surgery and local drug delivery became major research developments in the field of therapeutic ultrasound in the brain. Image-guided therapy using ultrasound, temporary opening of the blood-brain barrier, local drug delivery using acoustically active carriers or the controlled induction of cell modulations are major topics of current therapeutic ultrasound research activities. Besides conventional ultrasound techniques the development of high intensity focused ultrasound (HIFU) systems broadened the variety of potential applications significantly, including brain tumor treatment, stroke, neurodegenerative diseases or neuromodulation.

The rapidly increasing knowledge of disease mechanisms and progressing development in medical device technologies, such as ultrasound, provide new insights of how diseases might be treated in the near future. The activities in the field of therapeutic ultrasound are research areas at the interface of engineering and biomedical sciences with the highest future potential.

The presentation will give an overview of some of these applications using different ultrasound approaches and will provide an inside of current research activities in this field at the UCSD Brain Ultrasound Research Laboratory.

Wednesday, March 2, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Design and Analysis of Hybrid Airships

Dan Raymer

President
Conceptual Research Corporation
Playa del Rey, CA

Dan Raymer will discuss the design and analysis of hybrid airships. Raymer performed the initial design and analysis of the Ohio Airship “Dynalifter”, a hybrid flight vehicle combining hydrostatic lift from helium with aerodynamic lift from wings and a shaped hull. This concept avoids many of the problems of traditional airships since a large fraction of its weight is carried by aerodynamic lift. It lands like a normal aircraft, decelerating on a runway as its weight is transferred from the wings to the tires. It has substantial weight on its tires when sitting on the ground allowing it to withstand a gusty side wind. Compared to a normal aircraft, the dynamic lift airship has reduced drag when flown at low speeds and flies on much less power than a conventional aircraft carrying a similar payload. Raymer will discuss the advantages of such designs, how such design differs from normal aircraft design practice, and factors that influence the likely success of such projects.

Tuesday, March 8, 2011
10:30 PM
Hedco Neurosciences Building, Rm. 100 (HNB 100)

An Approach to Control of Dynamic Systems with Multiple Objectives

Dušan M. Stipanović

Associate Professor
Department of Industrial and Enterprise Systems Engineering
and
Control and Decision Group at the Coordinated Science Laboratory
University of Illinois at Urbana-Champaign
Urbana, Illinois

The challenges of controlling dynamic systems with multiple objectives are related to and furthermore include problems in multi-player dynamic games, multiobjective optimization, and decentralized control and estimation which all are known to be independently difficult and unsolved in general terms. The additional complexity is introduced through nonlinear dynamic models with delays and perturbations as well as various state, input and communication constraints. In this talk we will present a number of recent results in control of dynamic systems with multiple objectives based on a Liapunov-like approach as well as differentiable approximations of minimum and maximum and differential inequalities. We will show simulations of multi- vehicle systems achieving multiple objectives such as collision avoidance, trajectory tracking, control of formations of vehicles, and surveillance of compact domains. In addition a number of experimental results including autonomous and semi-autonomous (that is, teleoperated) ground vehicles (conducted in the Robotics Laboratory at the University of Illinois) and aerial vehicles (conducted at the Boeing Company in Seattle) will be presented.

Wednesday, March 9, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

The Seven Deadly Sins of Aircraft Design

Barnaby Wainfan

Technical Fellow
Northrop Grumman Aerospace Systems

This presentation examines mistakes that occur regularly in airplane design. The designs that result from these missteps fail. The failures can be technical, leading to machines that refuse to fly or are never completed. The failure can also be one of effectiveness; the aircraft is technically successful as a flying machine, but is economically unviable or unable to perform its mission. The goal of the presentation is to describe the most common of these failure types and to provide, through historical example, insight enabling recognition and avoidance of the most common traps early in the design process.

Wednesday, March 23, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

25 Years of Adaptive Structures – A Subjective Perspective

Jayanth N. Kudva

President
NextGen Aeronautics Inc.
2780 Skypark Drive, Suite 400
Torrance CA

While ‘smart materials,’ particularly piezoelectrics, have been known and used by the scientific community for more than a century, the term ‘smart structures’ came into vogue in the 1980s. The impetus for the research at that time was sparked by the initial demonstration of embedded fiber optic sensors in a composite laminate. Since then, hundreds of millions of dollars of R&D investment has been made in the broad area of smart or multi-functional materials and structures. This presentation traces the historical development of this field, starting from about the mid-80s to the present, in three areas:

  1. Health monitoring, mainly for structures, wherein sensors are attached or embedded in the structures to monitor its (internal) health, to increase safety, reliability and possibly increase the flight envelope;
  2. Integration of antennas and other sensors to provide multi-function capabilities at the component level—for instance provide optimal structural and antenna performance, enhancing overall system capability;
  3. Adaptive structures where sensors and actuators are integrated in the structure or the overall system to change shape or state to optimize its performance for differing external conditions such as loads and flight regimes. The rationale in this case is to provide multi-point optimization at the system level, for example to realize wing shapes which could be optimal across a wide speed range, resulting in multi-mission capabilities.

While much fundamental and applied research has been conducted in all three areas, transition of the developed technologies with demonstrated performance improvements has been limited. The reasons for this are many and varied; the presentation provides a broad brush, subjective, assessment of the overall R&D commercialization efforts in the field and a speculative vision of the future of smart structures.

Wednesday, March 30, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Shock Wave Adventures

Veronica Eliasson

Assistant Professor
Department of Aerospace & Mechanical Engineering
University of Southern California
Los Angeles, CA

A shock wave is a useful tool to generate very high pressures and temperatures. In particular, the energy from a shock wave can be focused and then generate even more extreme conditions. Applications on shock wave focusing range from medical treatment of kidney stones to supernovae collapse, and in this talk I will present some of the projects my group is working on. In particular we are interested in impact events where a strong fluid-structure coupling is present and has to be taken into account. In particular, we are interested in shock focusing in water and material effects with applications to marine structures, understanding the cause and how to prevent traumatic brain injury caused by blast waves, and effects of cavitation due to pulses propagating through fluid-filled cracks.

Wednesday, April, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Research Progress of the USC Nonlinear Dynamics Group

Eva Kanso

Associate Professor
Department of Aerospace & Mechanical Engineering
University of Southern California
Los Angeles, CA

I present some of the recent research activities at the USC Nonlinear Dynamics Group. In particular, I highlight the work of Fangxu Jing (PhD’11), Babak Oskouei (PhD’11) and Adam Ysasi (MS’10). The underlying theme is fluid-body coupling and the locomotion of aquatic animals. Much attention has been given recently to understanding how aquatic animals use fluid-body coupling to their advantage, thus achieving impressive maneuvers and hydrodynamic efficiencies. The approach of our research group is to investigate basic mechanisms by which idealized bodies swim in a perfect fluid. I discuss two types of locomotion: (i) active locomotion due to controlled body deformations, and (ii) passive locomotion due to energy harvested from ambient vorticity. I comment on the stability of motion in unsteady flows and conclude with the ongoing work of Andrew Tchieu (post-doc) on the finite dipole dynamical system as a model for fish schooling.

Wednesday, April 13, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Highly Turbulent Strained Premixed Flames in the Distributed Reaction Regime

Alessandro Gomez

Professor
Department of Mechanical Engineering
Yale University
New Haven, CT

Turbulent lean-to-stoichiometric premixed flames were experimentally studied in a counterflow configuration at turbulent Reynolds numbers on the order of one thousand. The primary objective is to examine conditions of departure from the flamelet regime and analyze the turbulent premixed flame structure under conditions in which disrupted and locally-extinguished flame fronts are expected.

A turbulent stream of fresh premixed reactants was opposed to a second stream of hot products of combustion. By varying temperature and composition of the combustion product stream, the “realities” of practical flames, such as heat losses and composition stratification, could be studied systematically in a well-defined system. These effects are not accounted for by the commonly used Borghi diagram of regimes of turbulent premixed combustion. Diagnostic techniques included PIV and simultaneous CO/OH-LIF to probe the structure of the oxidation layer.

It was found that the boundary between the flamelet regime and the distributed reaction zone was lowered significantly to turbulent Karlovitz numbers, Kat, of unity order. The oxidation layer was found to be sensitive to the turbulence intensity and the hot product composition. In fact, the quenching of the oxidation layer, that is not currently accounted for in turbulent combustion models, appeared to be a critical element of departure from the flamelet regime.

The interpretation of the experimental results was aided by ancillary numerical calculations of strained laminar premixed flames that showed two distinct extinction modes, an abrupt one and a smooth one, the latter being favored by an excess of oxidizing species in the combustion product stream.

The highly turbulent opposed jet system is shown to offer several advantages by comparison with the more common jet flames and is proposed as a benchmark for turbulent combustion studies.

Wednesday, April 20, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Deforming Composite Grids for Fluid Structure Interactions

Bill Henshaw

Centre for Applied Scientific Computing
Lawrence Livermore National Laboratory
Livermore California

For some years we have been developing an open source software framework called Overture for the solution of partial differential equations in complex moving geometry. We use overlapping grids (also know as overset or Chimera grids) to efficiently represent complex geometry with structured grids. I will begin this talk by giving a brief overview of Overture and its capabilities. The focus of the talk will be on our recent work for fluid structure interaction problems. I will describe the use of deforming composite overlapping grids for the solution of problems coupling fluid flow and deforming solids. The method is based on a mixed Eulerian Lagrangian technique. Local moving boundary-fitted grids are used near the deforming interface and these overlap non-moving grids which cover the majority of the domain. The approach is described and validated for some fluid structure problems involving high speed compressible flow and linear elastic solids.

Wednesday, April 27, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Integrated Computational Materials Science, Manufacturing and Engineering of Textile Polymer Composites

Anthony M. Waas

Felix Pawlowski Collegiate Professor of Aerospace Engineering
and
Professor of Mechanical Engineering (courtesy)

University of Michigan,
Ann Arbor, MI

Composite materials and structures made of textile architecture are a rapidly emerging, cost-effective technology for the manufacturing of large aerospace structures. At the Composite Structures Laboratory at UM, an integrated computational framework for textile polymer composites that includes a novel polymer curing model, has been developed and used in connection with modeling the manufacturing process of textile composites. The model is based on the notion of polymer networks that are continuously formed in a body of changing shape due to changes in temperature, chemistry, and external loads. Nonlinear material behavior is incorporated through nonlocal continuum damage mechanics that preserves mesh objectivity in finite element based calculations that go beyond maximum loads. The integrated model is applied to the curing of a textile composite made from carbon fiber tows and a thermoset polymer. The mechanical and chemical properties are measured during curing using concurrent Brillouin and Raman light scattering. It is shown that significant internal stresses can develop during cure. The effect of these stresses on the manufactured part performance, when subsequent service loads are applied, is evaluated and found to be in agreement with experimental observations. Subsequently, an engineering approach to evaluating the compressive strength of braided textile composites, while accounting for the manufacturing induced stresses, is developed and validated against experiments.

Monday, May 16, 2011
11:00 AM
Hedco Neurosciences Bldg. Rm. 100 (HNB 100)

Refreshments will be served at 10:45 pm.


Fall, 2011

Nanostructured Anodes for Next Generation Li-Ion Batteries

Katerina E. Aifantis

European Research Council Grantee
Department of Mechanics
Aristotle University of Thessaloniki
Greece
and
Adjunct Assistant Professor
Department of Physics
Michigan Technological University
Houghton, Michigan

The current and future applications of secondary Li-ion batteries range from powering cell phones and electric vehicles to biomedical devices. Extensive work is, therefore, being performed on further improving their lifetime and cyclability. Experimental research has yielded that Sn and Si can provide three-to-ten times the capacity of commercially used graphitic anodes. What inhibits the commercialization of such anodes, however, is the 300% volume expansion, and subsequent fracture, that Sn and Si experience upon maximum Li-insertion. This fracture is minimized by embedding nanosized Sn and Si in a matrix. In the present talk it will be shown how electrochemical cycling, transmission electron microscopy, and continuum mechanics can be employed to develop design criteria that predict the most optimum matrix material, as well the Sn particle size and inter-particle spacing, that will significantly limit fracture. Nanostructured Sn-based anodes will be shown that have a 100% capacity retention for 400 cycles.

Wednesday, September 7, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Applications of Molecular Gas Dynamics to MEMS Devices

Yen-Lin Han

Assistant Professor-in-Residence
Department of Mechanical Engineering
University of Connecticut

Continuing advances in MEMS fabrication capabilities have facilitated significant progress in miniature devices. This can be achieved by utilizing molecular gas dynamics phenomena such as mass separation, thermal edge, and thermal creep flows. Besides the better-known Knudsen Compressor, other examples, including a continuous trace gas preconcentrator, and a thermal bimorph micropump will be discussed.

A trace gas preconcentrator is commonly included in gas detection systems to increase the ultra low, yet dangerous trace gas concentration, to the level at which a detection unit can accurately determine the presence of the trace gas. The widely-used adsorption/desorption pre-concentrators interrupt gas flows for significant periods, in order to accumulate sufficient number of trace gas molecules, before they are released to the detection unit. The continuous Trace Gas Preconcentrator provides a unique approach, utilizing molecular gas dynamics theory to provide mass separation. In the continuous trace gas preconcentrator, the gas flow is not stopped and the time required to reach the proper concentration is significantly shorter than the adsorption/desorption method.

Using the rarefied gas dynamic phenomenon of thermal edge flow, a micropump with a built-in thermal bimorph microvalve is studied. This micropump contains an isolated heating element, made of thermal bimorph materials, that is serve as a heating element to initiate the flows, and to thermally activated bimorph valve. DSMC (Direct Simulation Monte Carlo) simulation results indicate the flow characteristics, including the maximum pressure ratio and mass flow rate vary with the bimorph valve lengths and the flow channel sizes. Finite element analysis of selected thermal bimorph structures has also demonstrated proper deflections of the thermal bimorph valve. Combining the flow and structural studies, the characteristics of the thermal bimorph micropump can be realized for future fabrication and experimental investigations.

Wednesday, September 21, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:00 pm.

Towards a Comprehensive Real-Time Aerosol Chemical Analyzer: Instrumentation Development and Field Results

Denis Phares

Associate Professor
Aerospace & Mechanical Engineering Department
University of Southern California
Los Angeles, CA

Real-time chemical analysis of atmospheric aerosols has been an active area of research for several decades. This need to determine the chemical nature of particulate matter in real-time stems from a continued lack of understanding of how atmospheric particles form, and their subsequent role in a variety of environmental processes and human health effects. The chemical complexity of ambient particles, which are generally composed of mixtures of metals, salts, and organics, contributes to the difficulty of the problem and merits an assessment of how successful field deployed instruments have actually been in reducing the associated uncertainties. This talk will focus on the history of aerosol mass spectrometers, the successes and limitations of each design, recent developments and field results, and a future outlook for the field.

Wednesday, September 28, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:00 pm.

Engineering Interfaces as a Strategy Towards New Materials for Extreme Irradiation Environments

Alfredo Caro

Materials Science and Technology Division
Los Alamos National Laboratory
Los Alamos, NM

The LANL’s Center for Materials under Extreme Mechanical and Irradiation Extremes, one of the DOE’s Energy Frontier Research Center, is focused on the study of interfaces and their response to extreme conditions. This talk will cover two aspects of this research: i- radiation resistance of nanoscale foams and ii- radiation resistance of twist boundaries in fcc and bcc metals. Using computational tools and experimental measurements we we explore the behavior of these two systems to unveil details on the evolution of radiation created defects as affected by nanoscale structural features.

Wednesday, October 5, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:00 pm.

Hydrodynamic Quantum Analogues: Droplets Walking on the Impossible Pilot Wave

John Bush

Professor of Applied Mathematics
Department of Mathematics
Massachusetts Institute of Technology
Cambridge, MA

Yves Couder and coworkers have recently reported the results of a startling series of experiments in which droplets walking on a vibrating fluid surface exhibit several dynamical features previously thought to be peculiar to the microscopic realm, including single-particle diffraction and interference, tunneling and quantized orbits. In an attempt to develop a connection between the fluid and quantum systems, we explore the Madelung transformation, whereby Schrödinger’s equation is recast in a hydrodynamic form. Doing so allows us to demonstrate that the capillary pressure associated with the fluid’s interfacial tension plays the role of the quantum pressure, and that the capillary Faraday waves play the role of de Broglie’s matter waves. A surprising correspondence between the walking droplets and de Broglie’s pilot wave theory of quantum mechanics is developed. New experiments are presented, and indicate the potential value of this hydrodynamic approach to both visualizing and understanding quantum mechanics.

John Bush is a Professor of Applied Mathematics at MIT. Having completed his BSc in Physics at University of Toronto, he went on to Harvard for his PhD in Geophysics, then the University of Cambridge for postdoctoral research. In 1998, he joined the faculty of MIT, where he is now the Director of the Applied Mathematics Laboratory. Bush’s research began in geophysics, but then shifted towards the effects of surface tension. In the past five years, he has been working primarily in biological fluid mechanics and biomimicry, with a view to rationalizing and exploiting Nature’s designs. Most recently, he has been exploring hydrodynamic analogues of quantum systems.

Friday, October 7, 2011
2:00 PM
Davidson Conference Center (DCC) Club Room

Appetizers will be served at 1:00 pm in the Vineyard Room.

Hydrodynamical Constraints on the Shape of Fishes and Trees

Christophe Eloy

Professor of Physics
Aix-Marseille University
France

During this talk, I will address two biomechanical problems of fluid-structure interactions. First, I will examine the relation between the shape of fishes and their performance in the case of undulatory swimming. Then, I will discuss how the resistance to wind-induced stresses constrains the architecture of trees.

Christophe Eloy is an Assistant Professor in Physics at Aix-Marseille University and at IRPHE in Marseille, France. He is currently a Marie Curie fellow at UC San Diego in the Department of Mechanical and Aerospace Engineering. His research area is mainly Theoretical Fluid Mechanics with specific interests in Rotating Flows, Hydrodynamic Instabilities, Aeroelasticity and Animal Locomotion.

Wednesday, October 12, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:00 pm.

Homogenization of Wave Equations Non-Separated Scales, High Contrast and Localized Bases

Houman Owhadi

Professor of Applied and Computational Mathematics and Control and Dynamical Systems
California Institute of Technology
Pasadena, CA

We show how to construct localized elliptic cell problems for the homogenization of wave equations with non-separated scales, high-contrast and arbitrary deterministic coefficients. Randomness, scale separation, mixing or “epsilon-sequences” are not required because the proposed method solely relies on the compactness of the solution space. The support of cell problems can be localized to arbitrarily small subsets of the whole domain and explicit approximation error estimates are obtained as a function of the size of those subsets. We show how this work extends to elastodynamics and atomistic to continuum upscaling. Various parts of this talk are joint work with L. Zhang, L. Berlyand, M. Desbrun, M. Federov, M. Desbrun, L. Kharevych and P. Mullen.

Houman Owhadi received his B.S., Ecole Polytechnique (France), 1994; M.S., Ecole Nationale des Ponts et Chaussees, 1997; Ph.D., Ecole Polytechnique Federale de Lausanne (Switzerland), 2001. He moved to Caltech as Assistant Professor from 2004-11, becoming Professor in 2011. His work focuses on the modeling and analysis of systems characterized by multiple scales, geometric structures, noise and uncertainties. At the center of his work are fundamental problems such as non-separated scales, anomalous diffusion, the geometric integration of multi-scale stochastic mechanical systems and the optimal quantification of uncertainties in presence of limited information.

Wednesday,October 19, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:00 pm.

Neutron Tomography For Material Characterization

Dayakar Penumadu

Fred N. Peebles Professor
and
Head of Joint Institute for Advanced Materials
and
Chair of Excellence

Civil and Environmental Engineering
University of Tennessee
Knoxville, TN
dpenumad@utk.edu

Three dimensional neutron imaging is becoming an increasingly important research tool and a diagnostic technique, providing complementary information to X-ray imaging for a wide range of applications in science and engineering. Using a well collimated neutron beam and lens coupled neutron detector system comprising of a thin scintillator screen, low-noise CCD camera, suitable mirror coupled to a high quality lens system in a light-tight box, varying resolution neutron radiography and tomography images are obtained for target materials and working systems in a controlled sample environment. In this presentation, author will present example results from his research group associated with neutron tomography of metals (steel and aluminum alloys), polymeric composites and sandwich structures, and granular materials under partial saturation. Relevant recent advances associated with energy selective neutron imaging including Bragg-edge imaging and dark-field tomography will also be included. As an example of in-situ diagnostic ability, neutron imaging of a working PEM fuel cell for water management studies will be addressed. The unique ability of neutrons to penetrate high Z materials and have extraordinary contrast to light elements such as hydrogen offers potential for many new applications. To demonstrate the multi-modality of using combined information from X-ray and neutron attenuation through matter, author will use the example results on partially saturated compacted sand sample and polymeric composites subjected accelerated sea environmental degradation conditions. Theses sample were imaged using X-ray (13.2 µm voxel size) and cold neutron (29.8 µm voxel size) tomography using unique imaging facilities at the Helmholtz- Zentrum-Berlin (CONRAD) and thermal neutrons (10 µm voxel size) at National Institute of Standards and Testing (BT2), Gaithersberg. Both imaging modality systems provide relatively large field of view (FOV) and high spatial resolution for engineering applications. High resolution tomography offers unprecedented opportunity to study materials non-invasively for evaluating the microstructure and damage characterization quantitatively in three dimensions. Direct integration of reconstructed images into numerical methods for solving boundary value problems is a promising future direction.

Wednesday, October 26, 2011
3:30 PM

Refreshments will be served at 3:15 pm.

The Global Dependence on Coal and How Oxy-Combustion Can Help

Richard L. Axelbaum

Jens Professor of Environmental Engineering Science
Department of Energy, Environmental and Chemical Engineering
Washington University in St. Louis
St. Louis, MO

The global demand for energy is rapidly rising, while at the same time there is growing concern that the continued use of fossil fuels, specifically coal, is irreversibly damaging our environment. Coal accounts for 50% of electricity production in the U.S., 80% in China and 75% in India. Why has coal become such an integral part of our energy mix? Does it need to be? Are there ways to utilize coal while having minimal impact on the environment? The first part of this talk will address these questions and give the audience an appreciation of the global challenges and possible solutions to our demand for clean, affordable energy. In the second part of the talk, one of the more promising solutions, Oxyfuel combustion with carbon capture and storage (CCS), will be described. Then the characteristics of oxy-fuel combustion will be addressed from a fundamental sense, and will be shown to have the potential to produce soot-free, stable flames provided the stoichiometric mixture fraction is sufficiently high. The reason for the suppression of soot chemistry under conditions of high stoichiometric-mixture-fraction will be discussed.
Wednesday, November 2, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:00 pm.

Permanent Non Coalescence and Nonwetting: Science and Applications

G. Paul Neitzel

Professor
and
Associate Chair for Graduate Studies

George W. Woodruff School of Mechanical Engineering
Georgia Institute of Technology
Atlanta, GA 30332-0405

Under the proper conditions it is possible to press together two drops of the same liquid without experiencing coalescence or to press a liquid droplet against a surface normally wetted by the liquid without wetting occurring. By permanent noncoalescence and nonwetting we distinguish cases in which the phenomena may be observed for unlimited time from transient examples such as two drops of liquid bouncing off one another or a liquid droplet bouncing off a solid wall. To achieve permanent noncoalescence or nonwetting, a mechanism is needed for establishing a lubricating film of surrounding fluid (usually air) and sustaining this film as the liquid/liquid or solid/liquid surfaces are moved toward each other.

This talk will address means for the establishment of such lubricating films and discuss measurements and theory conducted to understand the behavior of such systems. Finally, possible applications of permanent noncoalescence and nonwetting will be described, including a demonstration of droplet levitation above a solid surface using non-contact, optical methods and a technique for the generation of nanoliter-scale encapsulated droplets of varying volume ratio.

G. Paul Neitzel has been a Professor in The George W. Woodruff School of Mechanical Engineering at the Georgia Institute of Technology since 1990; he presently also serves as Associate Chair for Graduate Studies. Prior to arriving at Georgia Tech, he served for eleven years on the faculty of the Department of Mechanical and Aerospace Engineering at Arizona State University and worked ten years at the U.S. Army Ballistic Research Laboratory, during which time he received his Ph.D. in fluid mechanics from The Johns Hopkins University. He has conducted research on the hydrodynamic stability of unsteady swirling flows and flows associated with materials processing, vortex breakdown, suppression of coalescence/wetting and bioreactor fluid dynamics. He is a Fellow of the American Physical Society and the American Society of Mechanical Engineers, an Associate Fellow of the American Institute of Aeronautics and Astronautics and the recipient of a National Science Foundation Presidential Young Investigator Award and an Alexander von Humboldt Fellowship. He has served as a visiting professor at the Universität Karlsruhe (Germany), Imperial College of Science and Technology (London) and the Université d’Aix-Marseille II and a visiting scientist at Forschungszentrum Karlsruhe (Germany).

Wednesday, November 3, 2011
Time: TBA
Location: TBA

Variance Reduction for Efficient Stochastic Particle Simulation and Estimation

Matthew West

Assistant Professor
Department of Mechanical Science and Engineering
University of Illinois at Urbana-Champaign
Urbana-Champaign, Illinois

Stochastic particle methods are efficient numerical algorithms for the simulation and estimation of high-dimensional systems, such as population balance models for aerosol suspensions and particle filters for nonlinear filtering. While particle methods avoid the curse of dimensionality that limits grid-based numerical schemes in high dimensions, they can still be very expensive as the number of particles becomes large.

In this talk we present two new variance reduction schemes for particle methods for Markov jump systems. The first variance reduction scheme uses particle weighting functions for a single simulation to enable variable and adaptive resolution in particle space, thereby focusing computational resources on the system components contributing the greatest variance. The second variance reduction scheme couples multiple simulations in an anti-correlated ensemble by extending the classical antithetic and stratified sampling techniques to time-evolution Markov systems. Both of these variance reduction techniques are able to accelerate particle methods for stochastic jump systems by several orders of magnitude.

We apply these new reduced-variance particles methods to simulation and estimation problems in atmospheric aerosol dynamics and chemistry. By using variance reduction, we are able to simulate the largest particle-resolved models to date of ship-plume emissions and polluted urban scenarios, thus giving new insight into aerosol mixing states and their climate and health impacts.

Matthew West is an Assistant Professor in the Department of Mechanical Science and Engineering at the University of Illinois at Urbana-Champaign. Prior to joining Illinois he was on the faculty of the Department of Aeronautics and Astronautics at Stanford University and the Department of Mathematics at the University of California, Davis. Prof. West holds a Ph.D. in Control and Dynamical Systems from the California Institute of Technology and a B.Sc. in Pure and Applied Mathematics from the University of Western Australia.

Wednesday, November 9, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:00 pm.

A Fascination with Fluids: Vortices and Vortex Breakdown

Tony Maxworthy

Smith International Professor of Mechanical Engineering
Department of Aerospace & Mechanical Engineering
University of Southern California
Los Angeles, CA 90089-1191

The problem of the dynamics of long slender vortices, e.g., tornadoes, dust devils, waterspouts, fire whirls, internal flow in rotating machinery, leading edge and trailing vortices on lifting surfaces, etc, has been a fascination for me for close to 50 years. A sequence of experimental studies will be presented, together with reasoned physical explanations and related theoretical arguments, that attempt to bring some order to the sometimes-controversial discussion that has swirled about the subject during that time.

Tuesday, November 15, 2011
10:30 AM
Laufer Library, (RRB 208)

Refreshments will be served at 10:15 am.

Keeping the House Clean—The Control of Spacecraft Contamination

Hagop Barsamian

Section Manager
Contamination Control Engineering
Northrop Grumman Aerospace Systems
Space Systems Division
Redondo Beach, CA 90278

Contamination can degrade the performance of spacecraft systems. Accumulation of particulate and molecular contamination will cause undesired changes in optical, thermal control and guidance systems of spacecraft. These changes include increase in solar absorptance of thermal control surfaces, and the reduction in transmittance or scatter of light in optical systems. Identification of contamination sensitivities and quantification of the allowable contamination levels on these systems is a logical first step. Once identified, plans are implemented to mitigate the effects of contamination and maintain an acceptable level of hardware cleanliness. The controls that are put in place throughout the manufacture, assembly and testing of these spacecraft systems include selection of materials for the hardware design, use of cleanrooms to control the environment, and monitoring of contamination levels. These efforts will help minimize system performance degradation due to contamination and lead to mission success.

Wednesday, November 16, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:00 pm.

The Very Light Car

Barnaby Wainfan

Technical Fellow
Northrop Grumman Aerospace Systems
Redondo Beach, CA 90278

The Edison2 Very Light Car is the most efficient highway-capable 4-seat car in history. In 2010, the Very Light Car won the Mainstream Class of the Progressive Insurance Automotive X-Prize. The 4-seat VLC achieved over 100 MPG combined, while demonstrating highway-capable performance. Mr .Wainfan will discuss the design and development of the car, and the future of the VLC project and efficient road transport.

Wednesday, November 30, 2011
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Deconstructing (and Reconstructing) Wall Turbulence

Beverley J. McKeon

Professor of Aeronautics
Graduate Aerospace Laboratories
California Institute of Technology
Pasadena, CA

The literature contains several distinct approaches to understanding the flow physics underlying wall turbulence, including the characterization of velocity statistics and spectra, identification of dominant coherent structures and analysis of the amplification properties of the Navier-Stokes equations, to name a few. However the detailed connections between these views of the same fluid system have proved elusive. The critical layer framework for turbulent pipe flow proposed by McKeon & Sharma (J. Fluid Mech, 2010) provides a simple model by which to understand both qualitative and quantitative aspects of the structure of wall turbulence. This framework utilizes an input-output formulation of the Navier-Stokes equations to analyze the transfer function and identify the dominant forcing and response mode shapes at each combination of frequency, streamwise and spanwise wavenumbers relevant to experimental observations. In this talk I will describe and expand the framework, demonstrating that our model gives important predictive information about both the statistical and structural make-up of wall turbulence, and can be used to understand some simple experiments designed to manipulate the spectral distribution of turbulent energy. Implications for both the classical picture of wall turbulence and control of turbulent flows will be discussed.

Beverley McKeon is a Professor of Aeronautics in the Graduate Aerospace Laboratories at Caltech (GALCIT). Her research interests include interdisciplinary approaches to manipulation of boundary layer flows using morphing surfaces and fundamental investigations of wall turbulence at high Reynolds number. She was the recipient of a Presidential Early Career award (PECASE) in 2009 and an NSF CAREER award in 2008. Prior to joining GALCIT, she was a Royal Society Dorothy Hodgkin Research Fellow and postdoc in the Department of Aeronautics at Imperial College London, after receiving a B.A. and M.Eng. from the University of Cambridge (1996) and Ph.D. in Mechanical and Aerospace Engineering from Princeton University (2003) under the guidance of Lex Smits.

Thursday, December 8, 2011
11:00 AM
RTH 526

Refreshments will be served at 10:45 am.