2010 Seminar Archive


Spring, 2010

Bioinspired Flow Optimization

P. Koumoutsakos

Professor and Chair of Computational Science

ETH
Zurich, Switzerland
and
Millikan Visiting Professor
Caltech
Pasadena, CA

For centuries engineers have sought inspirations from nature in designing their creations. Along with the imitation of biological forms we may consider biological processes as optimization algorithms for engineering devices. In this talk I will present a framework for developing algorithms based on concepts such as biological evolution and bacteria chemotaxis. I will discuss the advantages and drawbacks of these algorithms in the context of their application to problems such as the multiobjective optimization of turbomachinery test rings and the reverse engineering of simulated anguiliform swimmers.

Wednesday, January 20, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Utilizing the Ignition Quality Tester (IQT™) to determine the impact of fuel physicochemical properties on Low Temperature Combustion (LTC)

Greg Bogin

Research Professor 
Chemical Engineering Department
Colorado School of Mines
Golden, CO 80401

The goal of increased combustion efficiency with reduced emissions has sparked increased interest in new technologies for advanced combustion engines such as Low Temperature Combustion (LTC). LTC involves the combustion of thoroughly premixed fuel and air, utilizing high compression ratios and lean equivalence ratios which produce relatively long ignition delay times (compared to typical diesel engines). LTC utilization produces two desirable characteristics: i) high engine efficiency due to high compression ratio and unthrottling, and ii) low NOx and PM emissions due to minimization of traditional high-temperature flame fronts and locally fuel-rich zones. LTC engines, however, present significant challenges as traditional engine control strategies (ignition coil control for Spark Ignition or start-of-injection timing for Compression Ignition) are not employed. Fuel mixture autoignition kinetics dictate ignition timing, resulting in significant control system decoupling. Attaining LTC using petroleum-based fuels (and eventually biofuels) is achievable through the optimal coupling of the fuel injection process with in-cylinder fluid mechanics, and an improved understanding of kinetic pathways to auto-ignition. This requires a concerted approach of experiments and numerical modeling to quantify the effects of fuel chemistry and physical properties on combustion timing, combustion efficiency, and emissions.

A comprehensive understanding of fuel effects on combustion efficiency and emissions is essential for predictive models used to design advanced combustion engines utilizing the LTC regime. It is also essential as non-petroleum based fuels, which can vary widely in fuel chemistry, are adopted. Accomplishing this task requires a research device capable of studying realistic fuels (e.g. low volatility) which are difficult to study using traditional research apparatus such as shock tubes and rapid compression machines. The Ignition Quality Tester (IQT™) is a constant volume, spray combustion device designed solely to measure ignition delay, from which a Derived Cetane Number (DCN) is calculated using ASTM method D6890-09. The experimental capabilities of the IQT have been expanded to allow investigation of fuel effects on combustion timing and emissions. In parallel, a computational fluid dynamics (CFD) model was developed using KIVA-3V and linked with CHEMKIN to provide the first significant insights into the coupling of fuel spray physics and chemical kinetics for the IQT. The coupling of experiments and modeling enables fundamental research on the physical and chemical fuel effects on combustion, with the benefit of maintaining the link to the ASTM method for DCN. The CFD model accurately and efficiently reproduces ignition behavior of n-heptane; predicting that the combustion event is governed by autoignition and that dispersed ignition events occur throughout the combustion chamber. 2-methyl-hexane (an isomer of n-heptane having similar physical properties) produces longer ignition delay (ID) times compared to n-heptane, in agreement with rapid compression machines studies. The longer ID of 2-methyl-hexane verifies that chemical kinetics dominate over the physical effects of the fuels. The longer ID also results in higher NOx emissions. Thus, the IQT can bridge the gap between fundamental fuel research and actual internal combustion engine research.

Wednesday, February 3, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Tuning the Properties of Materials Through Nanostructure: Processing of Large Sized Nanocomposites for Optical and Magnetic Applications

Javier E. Garay

Assistant Professor 
Department of Mechanical Engineering
Materials Science and Engineering Program
University of California, Riverside

Improved performance of devices such as high power lasers often hinge on the development of materials with a precise blend of properties. Nanocrystalline materials display significantly different properties and functionalities than their microcrystalline counterparts, yet their direct application in products has been hindered by the difficulty in producing them reliably and efficiently. One reason is that consolidation of nanocrystalline powders usually results in large grain size increase and therefore loss of enhanced nanocrystalline properties. Recently, the versatile material processing technique of current activated pressure assisted densification has proven effective in overcoming the grain growth challenge—it is now possible to efficiently produce materials large enough to be viable nanocrystalline parts. The method draws its effectiveness from large electric current densities that serve to heat the materials and also alter the processing kinetics. After an overview of our processing techniques, I will present results on large-sized, fully dense materials with grain sizes much less that 100 nm. The materials have very different properties than traditional materials including improved visible light transmittance, tailorable heat conductivity, and magnetic coupling and can be used as laser host ceramics, magnetic sensors etc. The results will be discussed in terms of crystal length scale effects and proximity of nanoscale phases.

Javier Garay received his B. S. in Mechanical Engineering (1999), M.S. in Materials Science and Engineering (2002) and Ph.D. in Materials Science and Engineering (2004) all from the University of California, Davis. In 2004 he was appointed assistant professor in the Bourns College of Engineering at UCR where his research focuses on advanced material processing and synthesis. Prof. Garay is the PI of a vibrant experimental laboratory called the Advanced Material Processing and Synthesis (AMPS) Lab. He is the recipient of two federal Young Investigator Program (YIP) awards: Army Research Office young investigator award (ARO-YIP) in 2005 and Air Force Office for Scientific Research young investigator award (AFOSR-YIP) in 2008. He also received the Faculty Early Career Development (CAREER) award from the National Science Foundation that will begin 2010.

Wednesday, February 10, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Turbulence in the Stratified Ocean

Sutanu Sarkar

Professor 
Mechanical and Aerospace Engineering Department
University of California at San Diego
La Jolla, CA

Background fluid stratification, often prevalent in the environment, inhibits vertical turbulent motion, allows wave-like motion, and promotes the formation of coherent structures. Quantification of the dynamical pathways that lead to mixing in spite of stable stratification is of critical interest to environmental modeling including local and regional impact of climate change. Our work utilizes high-resolution numerical resolution to understand links between turbulence, internal waves and coherent vortices. We will discuss the following examples from our recent work on turbulent flows in the ocean: a jet with non-uniform stratification as a model for vertical mixing in Equatorial Under Currents, a boundary layer on a sloping bottom as a model for mixing on a continental slope and finally the wake of a self-propelled submersible.

Wednesday, February 17, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Self-Assembly of Hierarchical Materials for Medicine and Energy

Samuel Stupp

Board of Trustees Professor of Materials Science, Chemistry, and Medicineand Director, Institute for BioNantechnology in Medicine (IBNAM) 
Department of Materials Science and Engineering, Department of Chemistry, Department of Medicine and Institute for BioNanotechnology in Medicine
Northwestern University
Evanston, Il 60208

One of the grand challenges in materials science is the development of self-assembly pathways to highly functional structures across scales. Based on biological systems, soft matter and hybrid materials are natural targets in this context. Highly designed small molecules, polymers, biomacromolecules, ionic solutions, and nanoparticles are all potential building blocks for the development of these self-assembling functional materials. In addition to materials with useful combinations of physical properties and controllable shapes, it is also interesting to develop structures that have adaptable and self-repair capabilities. In this lecture I will review self-assembly pathways developed in our laboratory for supramolecular materials using designed molecules. One of the pathways to be described generates a large diversity of bioactive one-dimensional nanostructures and networks that can signal cells to create new materials for regenerative medicine. The driving force for self-assembly in these systems includes hydrogen bond formation, hydrophobic collapse of molecular segments in aqueous environments, and both attractive and repulsive electrostatic forces. A second system to be described involves the self-assembly of polymers and small molecules into membranes or cell-like capsules with hierarchical structures that may find biomedical and energy applications. In these systems, self-repair of large defects occurs readily by re-exposure to building blocks and diffusion barriers can form by contact of two liquids in millisecond time scales. Other systems to be described include the formation of oriented structures with minimal mechanical force, and the formation of hierarchical hybrid materials with electronic properties of interest in energy targets.

Professor Samuel Stupp earned his B.S. in chemistry from the University of California at Los Angeles and his Ph.D. in materials science and engineering from Northwestern University in 1977. He was a member of the faculty at Northwestern until 1980 and then spent 18 years at the University of Illinois at Urbana-Champaign where he was appointed in 1996 Swanlund Professor of Materials Science and Engineering, Chemistry, and Bioengineering. In 1999, he returned to Northwestern as a Board of Trustees Professor of Materials Science, Chemistry, and Medicine, and later was appointed Director of Northwestern’s Institute for BioNanotechnology in Medicine. Professor Stupp is a member of the American Academy of Arts and Sciences, and fellow of the American Physical Society, American Association for the Advancement of Science, World Technology Network, and World Biomaterials Congress. His awards include the Department of Energy Prize for Outstanding Achievement in Materials Chemistry, a Humboldt Senior Award, the Materials Research Society’s Medal Award, and the American Chemical Society Award in Polymer Chemistry for his work on supramolecular self-assembly. Over the past few years, his invited lectures and visits to other institutions include, the Sir Edward Youde Memorial Visiting Professorship at Hong Kong University of Science and Technology, the Joliot Curie Professorship at Ecole Supérieure de Physique et de Chemie Industrielles in Paris, The Merck-Karl Pfister Visiting Professorship in Organic Chemistry at MIT, a Visiting Professorship at the Institut de Science et d’Ingenierie Supramoléculaires in Strasbourg, and the Israel Pollack Distinguished Lectures Award at the Technion in Israel. This year, he was elected fellow of the Materials Research Society and also received an honorary doctorate from the Eindhoven University of Technology in the Netherlands for revolutionary research in complex molecular systems. His research is focused on self-assembly and supramolecular materials with special emphasis in regenerative medicine, organic electronics, solar energy, and cancer therapies.

Wednesday, February 24, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Control and Suppression of Interfacial Instabilities by Shear

Stephen H. Davis

Walter P. Murphy Professor of Engineering Sciences and Applied Mathematics
and
McCormick School (Institute) Professor

Engineering Sciences and Applied Mathematics Department
Robert R. McCormick School of Engineering and Applied Science
Northwestern University
Evanston, IL 60208

There has been recent work on the control of instabilities using feedback and control theory to at least delay instability. Here, we shall discuss an alternative in which imposed shear flows can delay or eliminate interfacial instabilities though the shear triggers others that are less ‘harmful.’ This will be illustrated by the suppression of Van der Waals rupture instability in ultra-thin liquid films.

Stephen H. Davis received all his degrees at Rensselaer Polytechnic. He has been Research Mathematician at the RAND Corporation, Lecturer in Mathematics at Imperial College, London, and Assistant, Associate Professor and Full Professor of Mechanics at the Johns Hopkins University. He is Editor of the Journal of Fluid Mechanics and the Annual Review of Fluid Mechanics. He has authored 200 refereed technical papers in the fields of Fluid Mechanics and Materials Science and the book Theory of Solidification. He has twice been Chairman of the Division of Fluid Dynamics of the American Physical Society, is a Fellow of the American Physical Society, is a member of the National Academy of Sciences, the National Academy of Engineering, and the American Academy of Arts and Sciences, and was the 1994 recipient of the Fluid Dynamics Prize of the APS and the 2001 G. I. Taylor Medal of the Society of Engineering Science.

Wednesday, March 3, 2010
3:30 PM
Davidson Conference Center (DCC) Board Room

Refreshments will be served at 3:00 pm.

New Synthesis and Sintering Methods in Materials Research

Olivia A. Graeve

Associate Professor
Kazuo Inamori School of Engineering
Alfred University
2 Pine Street

This talk will present an overview of leading precipitation processes for the synthesis of nanostructured ceramic and metallic powders, with special emphasis placed on reverse micelle synthesis for the preparation of oxides and combustion synthesis for the preparation of borides. Specific examples will include the preparation of yttria-doped zirconia (Y-ZrO2) and lanthanum hexaboride (LaB6). The talk will also describe advanced sintering techniques for nanostructured materials.

For the case of Y-ZrO2, the thermal stability of the synthesized particles will be described. Transmission electron microscopy and Williamson-Hall analysis from x-ray diffraction have shown that the crystallite size ranges from 5-50 nm. A detailed study on the level of agglomeration and the particle size of the nanopowders will be described and corroborated using dynamic light scattering. Reaction parameters such as precursor concentration, aging time, and water-to-surfactant ratio were varied to optimize the synthesis process. Some of the powders were subsequently sintered using spark plasma sintering (SPS). Dense compacts of >98% density were obtained in 20 minutes.

The feasibility of preparing nanocrystalline LaB6 powders via a controlled combustion synthesis process will also be presented. These powders are extraordinarily strong electron emitters with applications in micro- and nano-satellite propulsions systems, where they can serve as substitutes for chemical propellants, such that the electrons being emitted by the material are the source of propulsion. The synthesis reaction for the preparation of the powders is described below.

During this process, controlled amounts of lanthanum nitrate (oxidizer) and boron were reacted with carbohydrazide (fuel) in a muffle furnace at 320°C. As the reactants were heated, the oxidizer and fuel reacted to form a fine violet powder that contains both nanocrystalline LaB6 and unreacted boron. After synthesis, the unreacted boron was removed from the powders using a controlled acid wash. The resulting phase-pure and faceted LaB6 powders were then characterized using x-ray diffraction for phase purity and crystallite size, and scanning electron microscopy for particle morphology.

Wednesday, March 10, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Electrospray and Its Applications

Daren Chen

Associate Professor
Department of Energy, Environmental and Chemical Engineering
Washington University in St. Louis
St. Louis, MO 63130

Electrospray technique (i.e., electrohydrodynamic atomization), has been proposed for many modern applications. Examples of the applications include the surface coating, agricultural treatments, emulsion, fuel spraying, micro-or nano- encapsulation, ink-jet printers, colloid micro-thrusters, electrospray mass spectrometry (ES MS) for macromolecular detection in biochemical applications, monodisperse super micro-and nono- particle generation, enhancement of droplet mixing, targeted drug delivery by inhalation, power production, and electrospray gene transfection. Among all the operational modes involved in electrospray process the cone-jet mode has been investigated and applied for the majority of above-described applications. It is because of its capability to produce un-agglomerated, monodisperse particles in the sub-micrometer and nanometer diameter ranges. Among different setups, single-capillary electrospray systems were often used in various applications. However, limitation of single-capillary electrospray is encountered in modern electrospray applications, especially in the biomedical and pharmaceutical areas. Dual-capillary electrospray (ES) technique was thus proposed to overcome the limit of a single-capillary electrospray system, thereby broadening the applications of electrospray technique. In this presentation we will first review the electrospray history and its fundamental principles, then present its modern applications in biomedical and pharmaceutical areas.

Thursday, March 24, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Morphing Surfaces for Flow Control

Beverley McKeon

Assistant Professor of Aeronautics
California Institute of Technology
Pasadena, CA

In this talk I will discuss opportunities for performance enhancement of aeronautical configurations using on-demand changes to surface morphology. It is well known that surface roughness can degrade the performance of aerodynamic bodies, for example by triggering early transition of laminar boundary layers or increasing skin friction drag in turbulent ones, but can we use this knowledge to our advantage? I will describe our work interrogating the response of different receptive flow configurations to this type of actuation, through experiments and computations, and demonstrating novel ways of reconfiguring modern materials to generate “morphing surfaces”, or thin skins capable of undergoing dynamic changes in surface roughness in response to low power inputs. Can we actively optimize the dimples on a golf ball for maximum range or directional correction? Not yet. …

Beverley McKeon has been an Assistant Professor of Aeronautics in the Graduate Aerospace Laboratories at Caltech (GALCIT) since 2006. 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.

Wednesday, March 31, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Microchannel Acoustophoresis in Biochips

Henrik Bruus

Professor
Department of Micro- and Nanotechnology
Technical University of Denmark
DTU Bldg. 345east
DK-2800 Kongens Lyngby
Denmark

Within the past five years there has been a significant increase in the number of novel applications of ultrasound standing waves for particle handling in microfluidic biochips. In spite of this growing interest, detailed measurements of the resonance line shapes are lacking. We present such measure­ments, published recently in Lab Chip 10, 563 (2010), based on tracking of individual polystyrene microbeads during acoustophoretic motion in straight water-filled microchannels in silicon/glass chips subject to piezo-induced ultrasonic pressure fields. From the measured line shapes we extract the corresponding Q-values and thus gain insight in the nature of the acoustic energy dissipation in such systems. The talk will end with examples of on-chip in vivo acoustophoresis of cells.

Wednesday, April 7, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Physical Constraints of Small-Scale Motility in Fluids

Eric Lauga

Assistant Professor
Department of Mechanical and Aerospace Engineering
University of California, San Diego
La Jolla, CA 92093-0411

Hydrodynamics plays a crucial role in many cellular processes. One example is the locomotion of cells such as bacteria, spermatozoa, and essentially half of the microorganisms on earth. These organisms typically possess flagella, slender whiplike appendages which are actuated in a periodic fashion in a fluid environment, thereby giving rise to propulsion. Motivated by recent experimental data, we consider in this talk three problems on the nonlinear hydrodynamics of swimming cells. We first address the observed flagellar synchronization between eukaryotic cells swimming in close proximity. We then discuss the locomotion of cells in complex (polymeric) fluids. We finally explain why cells swimming in confined environments are attracted to nearby boundaries.

Wednesday, April 14, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

On the Limiting Behavior of Regularizations of the Euler Equations with Vortex Sheet Initial Data

Monika Nitsche

Associate Professor
Department of Mathematics
University of New Mexico, Albuquerque

The vortex sheet is a mathematical model for a shear layer in which the layer is approximated by a surface. Vortex sheet evolution has been shown to approximate the motion of shear layers well, both in the case of free layers and of separated flows at sharp edges. Generally, the evolving sheets develop singularities in finite time. To approximate the fluid past this time, the motion is regularized and the sheet defined as the limit of zero regularization. However, besides weak existence results in special cases, very little is known about this limit. In particular, it is not known whether the limit is unique or whether it depends on the regularization. I will discuss several regularizing mechanisms, including physical ones such as fluid viscosity, and purely numerical ones such as the vortex blob and the Euler-alpha methods. I will show results for a model problem and discuss some of the unanswered questions of interest.

Professor Nitsche received her PhD degree in 1992 from University of Michigan Ann Arbor under the guidance of Prof. Robert Krasny. She held various postdoctoral position (UC Boulder, IMA, OSU, Tufts) until she joined the faculty of the department of Mathematics at the University of New Mexico, Albuquerque in 1999. Her research interests lie in the numerical study of vortex flows and the development of numerical methods for such flows. She has also done some work on internal waves in density stratified flows.

Wednesday, April 21, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

Is the Current Dominant Aircraft Configuration Optimal?

R.J. Huyssen

Managing Director
Diomedes Innovations, Ltd.
Pretoria, South Africa

and
Ph.D. Student
North West University
Pretoria
South Africa

Given that flight efficiency is governed by the laws of nature it is reasonable to expect that a dominance would emerge in the way that aircraft designers configure aircraft for various flight objectives. Such dominance has already established itself from the early years of human aviation and indeed prevails today. One might conclude that this configuration represents the optimal configuration for the majority of design objectives. Yet, this does not seem to be the case. Is there perhaps another aircraft configuration which could offer better flight efficiency to the majority of flight objectives? In the light of the adverse environmental impact of aviation we are obliged to meet our flight objectives in the most efficient way and should therefore consider this question very seriously.

In this talk, we shall place the Exploitation of flight into the general context of Possibility, Opportunity and Discovery to explain the existence of the current dominate aircraft configuration. A careful rethinking of the engineering process of Design in relation to the natural process of Evolution then allows us to analyse the observed differences in the evolved dominant configuration and that engineered today. We may then answer the question as whether this difference should exist at all.

Friday, April 23, 2010
2:00 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

Aerodynamics of Nano-Flyers

Daniel Weihs

Distinguished Professor
Faculty of Aerospace Engineering and Autonomous Systems Program
Technion—Israel Institute of Technology
Haifa, 32000, Israel

Some of the smallest flying insects have unique comb-like wings, with non-continuous surfaces. These have span lengths of mm size. In this talk, I will analyze the aerodynamics of such surfaces, showing how they can produce lift at Reynolds numbers of o(1). These findings are then used to build and test artificial nano-flyers of mm size wingspan and several generations of such nano-gliders and nano-flyers will be shown and future developments discussed.

 

 

 

 

 

 

 

 

Distinguished Professor Daniel Weihs of the Technion Faculty of Aerospace Engineering holds the Richmond Chair in Life Sciences at the Technion and is Chairman of the Israel National Committee for Space Research and head of the Technion Autonomous Systems Program. He is a a foreign member of the U.S. National Academy of Engineering and Fellow of the American Physical Society.

Prof. Weihs received his bachelor’s, master’s and doctoral degrees at Technion from 1964 to 1971. Prof. Weihs worked at the University of Cambridge, England 1971-1973, returned to the Technion as a senior lecturer in 1973; he was appointed full professor in 1983 and distinguished professor (one of only 5 at the Technion) in 2002. Part of the Technion leadership for many years, Prof. Weihs has served as Provost, Dean of the Graduate School and of the Faculty of Aerospace Engineering, Director of the Samuel Neaman Institute for Advanced Studies in Science and Technology and Director of the Asher Space Research Institute.

Throughout his career, Prof. Weihs has consulted for the Israeli ministries of Defense, Internal Security, Commerce & Industry, Science, and for public and private organizations in Europe, the United States and Canada, including NASA, NOAA, IBM and Atlas-Copco. He has been on the board of firms such as Israel Aircraft Industries, Beth Shemesh Engines, Israel Limnological and Oceanographic Research Corp, and Teuza-Fairchild VC fund, and of Ben Gurion University and Holon Institute of Technology. He has been a member of the Steering Committee of the Israel Space Agency for 20 years and head of its Scientific Satellite Sub-Committee. He has published more than 140 scientific papers and one book, and has lectured throughout the world on subjects of biofluid dynamics, aerospace engineering and life sciences.

Wednesday, April 28, 2010
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.


Fall, 2010

Verification and Control of Hybrid Systems with Application to Multiple Coordinating UAVs

Claire J. Tomlin

Professor
Electrical Engineering and Computer Sciences
College of Engineering
University of California at Berkeley
Berkeley, CA

This talk will present reachability analysis as a tool for model checking and controller synthesis for hybrid systems. We consider the problem of guaranteeing reachability to a given desired subset of the state space, allowing for nonlinear dynamics in each discrete mode, and possibly non-convex state constraints. Techniques from hybrid system verification are presented and used to compute reachable sets, under bounded model disturbances that vary continuously, as well as under the effects of sampling and quantization. The resulting control policy is an explicit feedback law involving both a selection of continuous inputs and discrete switching commands at each time instant, based upon measurement of system state. We discuss real time implementations of this, and present several examples using our UAV testbeds as well as Boeing aircraft.

Wednesday, September 8, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

In situ Microscopy and Spectroscopy Studies of Epitaxial Graphene on Metal Surfaces

Suneel Kodambaka

Assistant Professor
Dept. Materials Science and Engineering
University of California Los Angeles
Los Angeles, CA 90095

The recent discovery of two-dimensional (2D) graphene crystals has generated a lot of attention owing to its potential for applications in high-performance, low-power, electronics and as transparent conductors. Recent efforts focused on, and succeeded in, the fabrication of large-area graphene on a variety of substrates, an encouraging step toward realization of graphene-based devices. Yet, relatively little is known concerning the mechanisms underlying the growth of graphene and the role of substrate-graphene interactions on its electronic properties. As a first step, we focused on the development of an atomic-scale understanding of the growth and electronic structure of graphene on model metals such as Pd and Ni.

Using scanning tunneling microscopy and spectroscopy (STM and STS), in combination with density functional theory (DFT), we investigated the morphology and electronic structure of monolayer graphene grown on Pd(111) and on 3D facetted Ni islands. On Pd(111), we observe the formation of monolayer graphene islands, 200-2000 Å in size, bounded by Pd surface steps. Surprisingly, we found that graphene islands, as large as 2000 Å, are semiconducting with a bandgap of 0.3 eV. For graphene on Ni, we observed hexagonal and stripe moiré patterns with periodicities of 22 Å and 12 Å, respectively, on (111) and (110) facets of the islands. Graphene domains are also observed to grow, as single crystals, across adjacent facets and over facet boundaries. STS data indicate that the graphene layers are metallic on both Ni(111) and Ni(110). DFT calculations support all of our observations and indicate the presence of strong interactions between carbon and metal atoms. Our results suggest that electronic properties of epitaxial graphene can be tailored by the appropriate choice of substrate and the possibility of preparing large-area epitaxial graphene layers even on polycrystalline surfaces.

Wednesday, September 22, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

Engineering in Cardiac Electrophysiology

David Cesario

Assoc. Prof. of Medicine
Cardiac Electrophysiology
Keck School of Medicine
USC
Los Angeles, CA

Cardiac electrophysiology is a field with tremendous interaction between engineering and medicine. On a daily basis we use tools such as implantable pacemakers to improve patient’s lives by increasing their heart rates. We also place implantable cardioverter defibrillators that have the potential to rescue patients from life threatening arrhythmias. Additionally, we use tools to map abnormal heart rhythms to their exact location within the heart and then to ablate the abnormal cardiac arrhythmias, potentially curing these arrhythmias. The goal of this talk is to expose students to some of the engineering technology that is used in cardiac electrophysiology to better patients lives and improve their health.

Wednesday, September 29, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

On Growth and Form: Mathematics, Mechanics and Morphogenesis

L. Mahadevan

Lola England de Valpine Professor of Applied Mathematics
and
Professor of Organismic and Evolutionary Biology

Department of Organismic and Evolutionary Biology
School of Engineering and Applied Sciences
Harvard University
Cambridge, MA

The growth and form of a soft solid pose a range of problems that combine aspects of mathematics, physics and biology. I will discuss some examples of growth and form in the plant and animal world motivated by qualitative and quantitative biological observations at the molecular, cellular and tissue level. In each case, we will see how a combination of physical experiments, mathematical models and simple computations allow us to unravel the basis for the diversity and complexity of biological form, while suggesting a rich new lode of problems in geometry and analysis.

Wednesday, October 6, 2010
3:30 PM
Davidson Conference Center (DCC) Board Room

Refreshments will be served at 3:00 pm.

Nanoscale Materials for Energy Applications

Juergen Biener

Scientist
Nanoscale Synthesis and Characterization Laboratory
Lawrence Livermore National Laboratory
Livermore, CA

Enrico Fermi reputedly said, “God made the solid state. He left the surface to the devil” to describe the fact that surfaces and interfaces are difficult to treat theoretically due to their complex nature. In this talk I will show that one can exploit this complexity to design tunable interface-controlled high-surface-area materials for energy applications. Although the influence of surfaces on the bulk of the material is generally considered to be small, the presence of surfaces and interfaces can start to dominate the overall material behavior. This allows one to create new, tunable materials with mechanical, physical and chemical properties that are no longer determined by the bulk material, but by their nanoscale architectures. In this talk, I will focus on monolithic nanoporous materials to demonstrate the tunability of nanoporous solids for sustainable energy applications.

Work at LLNL was performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

Wednesday, October 13, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

Friction-Induced Reverse Chatter in Rigid-Body Mechanisms with Impacts

Harry Dankowicz

Associate Professor
Department of Mechanical Science and Engineering
College of Engineering
University of Illinois at Urbana-Champaign
Urbana, IL

This talk reviews recent work on the possibility of formulating a consistent and unambiguous forward-simulation model of rigid-body mechanical systems with isolated points of intermittent or sustained frictional contact. The analysis considers paradoxical ambiguities associated with the coexistence of sustained contact and one or several alternative forward trajectories that include phases of free-flight motion. The presentation documents the original discovery of an apparently irresolvable, infinitely degenerate ambiguity known as reverse chatter—a transition to free flight through an infinite sequence of impacts with impact times accumulating from the right on a limit point and with impact velocities diverging exponentially away from the limit point, even where the contact-independent normal acceleration supports sustained contact. The conclusions of the theoretical analysis are illustrated through everyday examples of chattering contact.

Harry Dankowicz is an Associate Professor in the Department of Mechanical Science and Engineering at the University of Illinois at Urbana-Champaign and has held faculty positions in the Department of Engineering Science and Mechanics at Virginia Polytechnic Institute and State University and in the Department of Mechanics at the Royal Institute of Technology (KTH) in Stockholm, Sweden. He received his M.S. degree (1991) in Engineering Physics from KTH; and his Ph.D. degree (1995) in Theoretical and Applied Mechanics with minors in Mathematics and Astronomy from Cornell University. Prof. Dankowicz is the recipient of several prestigious awards, including a Junior Individual Grant from the Swedish Foundation for Strategic Research and a Presidential Early Career Award for Scientists and Engineers from NSF. As director of the Applied Dynamics Laboratory at UIUC, he conducts dynamical systems research at the intersection of engineering, math and physics. This work involves studying a wide range of complex systems that are governed by differential equations and learning the behavior of those systems through theory and experiments. His research efforts further seek to make original and substantial contributions to the development and design of existing or novel devices that capitalize on system nonlinearities for improved system performance.

Wednesday, October 20, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

Fluid Dynamics and Transport in the Posterior Segment of the Eye

Anita Penkova

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

The fluid and solute transport in the posterior segment of the eye (vitreous humor and retina) takes place by complex transport mechanisms and processes which have not been fully examined and quantitatively explained in either healthy or diseased eyes. Among the goals of the ongoing research is to develop mathematical models based on experimental data for ocular fluid flow with twofold objectives: (1) to understand the fluid dynamics and transport in healthy and diseased eyes; and (2) to effectively deliver drug-based treatment for the latter. To effectively transport drugs to the retinal area, the transport mechanisms need to be understood and the relevant transport parameters (such as permeabilities and diffusion constants) in the various components of this highly complex structure need to be measured and quantified. To fully model the transport processes, the permeability of the RPE (retinal pigment epithelium) under various circumstances needs to be measured. While a healthy eye maintains a steady and well-regulated flow of fluids throughout the system, diseases can cause disruption to this process. Diseases such as diabetic retinopathy (DR) can cause partial blockage of the RPE and subsequent swelling due to fluid accumulation in the affected regions accompanied by vision impairment. The ongoing research includes the creation of DR conditions by exposing a bovine eye to 25 mM glucose for 24 hours, and measuring the permeability of the RPE together with an eye treated in 5.5 mM glucose as a control. With current experiments, it has been observed that exposure to glucose increases the transepithelial resistance, indicating some suppression of ionic pumping. These procedures are also being conducted for based experimentally grown fetal RPE cells (in-vitro).

Other interesting areas, particularly for drug delivery, include the transport in an aged human eye for which the vitreous humor has a heterogeneous character (gel and liquid) that complicates the mathematical modeling. While the gel may be treated as a porous medium described by Darcy flow, the remaining portion has to be modeled as Stokes flow. The current research on ocular drug delivery includes the modeling of transport through this complex structure and an experimentally-based development of the boundary conditions where the vitreous humor contacts the retina, the lens and the hyaloid, together with continuity conditions at the gel-liquid interfaces.

Wednesday, October 27, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

Fluid-Structure Interaction In Launch Vehicle Feedlines During Boost Phase of Flight

Kirk Dotson

Structural Dynamics Department/Structural Mechanics Subdivision
The Aerospace Corporation
El Segundo, CA

In structural modeling of launch vehicles, liquid propellant is sometimes rigidly attached to feedline walls. This assumption precludes the interaction of structural modes with propellant pressure and flow. An analysis of fluid-structure interaction (FSI) for the Atlas V launch vehicle revealed that structural models with rigidly-attached propellant yield unconservative response predictions under some conditions. In particular, during the maximum acceleration time of flight, pressure oscillations acting at bends in the Atlas V liquid oxygen feedline excite 15-20 Hz structural modes that have considerable gain on the feedline and at the spacecraft interface. The investigation also revealed that the venting of gas from the pogo accumulator is an excitation source and changes the dynamic characteristics of the hydraulic system. The FSI simulation produced during the investigation can be adapted to mission-specific conditions, such that responses and loads are conservatively predicted for any Atlas V flight.

Wednesday, November 3, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

Design and Fabrication for Biologically Inspired Robotics

Michael T. Tolley

Assistant Professor
Dept. of Mechanical and Aerospace Engineering
University of California, San Diego
La Jolla, CA

Robotics has the potential to address many of today’s pressing problems in fields ranging from healthcare to manufacturing to disaster relief. However, the traditional approaches used on the factory floor do not perform well in unstructured environments. I believe the key to solving many of these challenges will be to explore new, non-traditional designs. Fortunately, nature surrounds us with examples of novel ways to navigate and survive in the real world. Through evolution, biology has already explored myriad solutions to many of the challenges facing robotics. At the UC San Diego Bioinspired Robotics and Design Lab, we seek to borrow the key principles of operation from biological systems, and apply them to engineered solutions. In this talk I will discuss approaches to the design and fabrication of soft robotic systems, as well as systems which achieve self-assembly by folding.

Michael T. Tolley is assistant professor of mechanical and aerospace engineering, and director of the Bioinspired Robotics and Design Lab at the Jacobs School of Engineering, UC San Diego (bioinspired.eng.ucsd.edu). Before joining the mechanical engineering faculty at UCSD in the fall of 2014, he was a postdoctoral fellow and research associate at the Wyss Institute for Biologically Inspired Engineering and the School of Engineering and Applied Sciences, Harvard University. He received the Ph.D. and M.S. degrees in mechanical engineering with a minor in computer science from Cornell University in 2009 and 2011, respectively. He received the B. Eng. degree in mechanical engineering from McGill University in Montreal in 2005. His research interests include biologically inspired robotics and design, origami-inspired fabrication, self-assembly, and soft robotics.

Wednesday, November 4, 2015
3:30 PM
Seaver Science Library, Room 150 (SSL 150)

Refreshments will be served at 3:15 pm.

The Convective Modoki:
The Linear and Nonlinear Dynamics of Real Flows

Jean-Marc Chomaz

Laboratoire d’Hydrodynamique (LadHyX)
CNRS-Ecole Polytechnique
91128 Palaiseau Cedex

Novel and versatile numerical tolls are used to compute the stability of complex real flows as recirculation bubble, impinging jets, 2D or 3D wakes. Receptivity to perturbation, to blowing and suction, to base flow modification and nonlinear coupling between modes may be accessed by formulating the adjoint problem. Computation of the adjoint global mode show that both the lift-up mechanism associated to the transport of the base flow by the perturbation and the convective nonnormality associated to the transport of the perturbation by the base flow explain the properties of the flow. In particular, a compact wave maker region may be rigorously defined where control will be efficient and nonlinear interaction take place. Application to the nonlinear dynamics of the wake of a disk and of vortex induced vibration will be discussed.

Wednesday, November 17, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

Falling Clouds of Particles

Élisabeth Guazzelli

Associate Professor
IUSTI – CNRS
Polytech’Marseille
Marseille, France

The time evolution of clouds of particles settling under the action of gravity in an otherwise pure liquid is investigated both experimentally and numerically. It is found that an initially spherical cloud containing enough particles is unstable even in the complete absence of inertia. The cloud slowly evolves into a torus which breaks up into secondary droplets which deform into tori themselves in a repeating cascade. The discrete nature of the particles is fundamental in the understanding of these instabilities. Faster breakup is observed for clouds of anisotropic particles such as fibers due to the self motion of the anisotropic particles. When inertia is finite, the cloud also deforms into a flat torus that eventually destabilizes and breaks up into a number of secondary droplets. While this behavior bears some similarity with that observed at zero-inertia, the underlying physical mechanisms differ. Moreover, the evolution of the cloud deformation is accelerated as inertia is increased. Two inertial regimes where macro-scale inertia and micro-scale inertia become successively dominant are clearly identified.

Élisabeth Guazzelli is Senior Researcher (Directeur de Recherche) at the CNRS (Centre National de la Recherche Scientifique) and affiliated with the IUSTI Laboratory of Polytech’Marseille (Aix-Marseille Universite), of which she is Vice Director. A physicist by training, her research interests are in the field of particulate multiphase flows, such as granular media, fluidized beds, suspensions, and sedimentation. She is responsible for a very active and diversified research group in Marseille composed of ten people. Since 2005, she has been an Associate Editor of the Journal of Fluid Mechanics.

Friday, November 19, 2010
11:00 AM
Location: Hedco Neurosciences Building, Room 100 (HNB 100)

Ratchets in Fluid Transportation and in Biological Locomotion

Jun Zhang

Associate Professor
Department of Physics
and
Courant Institute of Mathematical Sciences
New York University
New York, NY

I discuss several cases where a broken symmetry—either broken spontaneously or by construction—leads to ratcheting behavior in systems where dynamic boundaries interact with moving fluids. Two examples feature reciprocal forcing combined with geometric anisotropy of boundaries. In one case a solid body can be made to hover stably, and in another, a fluid is efficiently pumped. I will also discuss the dynamics of a symmetric wing whose forward flight follows from a symmetry breaking instability, and how this dynamics is affected by the introduction of more biological realism.

Wednesday, December 1, 2010
3:30 PM
Stauffer Science Lecture Hall, Room 100 (SLH 100)

Refreshments will be served at 3:15 pm.

Turbulent Rotating Convection

Herman Clercx

Professor
Technische Universiteit Eindhoven
Eindhoven, Netherlands

Rayleigh-Bénard convection is a classical problem in which a fluid layer enclosed between two parallel horizontal walls is heated from below and cooled at the top. In a rotating frame of reference the dynamics can change considerably through the fundamental involvement of a combination of buoyancy and Coriolis forces. The rotating Rayleigh-Bénard (RRB) setting is important for many applications, e.g., in engineering and climate modelling.

Direct numerical simulation (DNS) is used to calculate the heat transfer, flow structuring and small-scale turbulent properties at systematically varied rotation rates. The DNS code solves the incompressible Navier-Stokes equations in a cylinder in a rotating frame of reference, coupled to the heat equation within the Boussinesq approximation. The results from the DNS will be compared to data from SPIV measurements in a water-filled cylindrical convection cell.

In particular, the fate of the Large Scale Circulation, present in non-rotating RB convection, and enhanced heat transfer under influence of increasing rotation rate will be discussed in this talk.

Wednesday, December 8, 2010
3:15 PM
Laufer Library (RRB 208)