Conferences, Lectures, & Seminars
Events for November
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Geophysical Vortex Streets: The Dynamics that Determines The Late-Time Behavior
Wed, Nov 01, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Phil Marcus Professor of Fluid MechanicsDepartment of Mechanical Engineering University of California at Berkeley Berkeley, CA Rotating, stratified 3D flows often act as if they were nearly 2D and the inverse cascade of energy often leads to large, turbulent vortices and jets. In general, the flows are not unique, and there are several basins of attraction of the flow - each characterized by its own pattern of vortices and jet streams. The transport properties of each pattern vary markedly, so in a geophysical, or climate-change context, the robustness of each pattern and how patterns are selected due to small changes in the environment are important. We explore pattern selection, and present a physical model that works well in correctly predicting the outcomes of long-term numerical simulations. This study was originally motivated by the behavior of the long-lived vortical storms on Jupiter, and we show the relationship between the results of this study and Jupiter's new (as of March 2006) red spot.
Location: Stauffer Science Lecture Hall, Rm 100
Audiences: Everyone Is Invited
Contact: April Mundy
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Observations of Ice Sheet Dynamics in a Warming Climate from Space
Wed, Nov 08, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Eric Rignot Senior Research Scientist
Jet Propulsion Laboratory
National Aeronautics and Space Administration
Pasadena, CA A little over ten years ago we knew very little about the state of mass equilibrium of ice sheets in Antarctica and Greenland. The nature of our knowledge has changed considerably with the advent of satellite techniques capable of measuring ice motion, surface elevation and more recently gravity. In this presentation, I will review the technique I have been using for the past ten years to study glacier dynamics in Greenland and Antarctica and determine their state of mass balance: satellite radar interferometry. It has been employed to detect ice motion, grounding lines, flow speed up and other detailed features associated with ground water migration at an unprecendented level of precision and spatial details. I will discuss how it has been used in combination with other data to come up with new estimates of the present-day evolution of ice sheets, how these results compare to other techniques (some of which published results as recently as a few weeks ago), and how these results (do not) match predictions made by numerical models that international panels of experts rely on to predict future sea level rise. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Admistration's Cryosphere Science Program.Location: Stauffer Science Lecture Hall, Rm 100
Audiences: Everyone Is Invited
Contact: April Mundy
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Biomedical Ultrasound
Wed, Nov 15, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Kirk Shung Professor of Biomedical Engineering Medical Ultrasonic Transducer ResourceUniversity of Southern California
Los Angeles, CA 90089-1111 Ultrasound has been used in medicine for many years. There are two major applications of ultrasound: diagnosis and therapy. As a diagnostic tool, its major advantages over other imaging modalities like magnetic resonance imaging, x-ray, CT and nuclear imaging lie in that it is non-invasive, capable of producing images in real-time, more cost-effective and portable. Ultrasound has been found to be of clinical value in many medical disciplines including OB/GYN and cardiology. As the frequency is further increased, applications in ophthalmology, dermatology and small animal imaging are being explored.Location: Stauffer Science Lecture Hall, Rm 100
Audiences: Everyone Is Invited
Contact: April Mundy
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Energy Loss Mechanisms in Micromechanical Resonators
Thu, Nov 16, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Dr. Julie Zhili HaoAssistant ProfessorDepartment of Mechanical EngineeringOld Dominion UniversityNorfolk, VirginiaABSTRACT
Micromechanical resonators are of great interests for a wide range of applications, such as rotation rate sensors (gyroscopes), electrical filters, and physics research instruments. For their practical applications, quality factors (Q) or energy loss mechanisms of micromechanical resonators are of critical importance, as a higher Q in these devices translates to higher sensitivity, lower motional resistance, better stability, and lower power consumption. Therefore, it is desirable to design and fabricate micromechanical resonators with ultra-high Q or very little energy loss. To this end, we need to understand and analyze energy loss mechanisms in such devices, not only for improving their performance, but also for establishing the fundamental limit of the Q. In fact, arising from its own nature, each loss mechanism in a micromechanical resonator exhibits a unique phenomenon that is governed by its related theory and can be analytically expressed and experimentally characterized. In this talk, I will discuss the analytical and experimental study on support loss and thermoelastic damping (TED) in micromechanical resonators. From this study, the closed-form expressions for their quantitative evaluation are obtained, shedding significant insights into the geometrical design and choice of materials in high-Q micromechanical resonators.BIO
Julie Z. Hao received the B.S and M.S. degrees in Mechanical Engineering from Shanghai Jiao Tong University, Shanghai, in 1994 and 1997, respectively. She received her doctoral degree in Mechanical Engineering from the University of Central Florida in 2000. Her dissertation topic was the research and development of a MEMS-based cooling system for microelectronics. After graduation, Dr. Hao worked as a MEMS Engineer in industry for two years and was involved in the development of optical MEMS and microfluidic products. From 2002-2006, she worked in the Integrated MEMS Laboratory at the School of Electrical and Computer Engineering, Georgia Institute of Technology. In July 2006, Dr. Hao joined the Department of Mechanical Engineering, Old Dominion University. Her research focuses on the development of MEMS devices for sensory, biomedical, and communications applications. These include high precision gyroscopes, bulk-mode resonators, high-Q biosensors, as well as microfluidic devices. Also, Dr. Hao works on the analytical and experimental study of complex multidisciplinary micromechanics that is critical for the performance of MEMS devices and microsystems.
Location: Laufer Library, RRB 208
Audiences: Everyone Is Invited
Contact: April Mundy
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Engineering New Treatments for Cardiovascular Disease Via Optimal Design and Physiologic Simulation
Fri, Nov 17, 2006 @ 01:00 PM - 02:00 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Alison L. Marsden, Ph.D. Postdoctoral Fellow
Stanford University
Stanford, CA Rigorous modeling and optimization of treatments for cardiovascular disease according to engineering principles provide a framework for testing new surgeries and interventions at no risk to patients. Ultimately these tools have the potential to complement doctors' clinical judgement and experience to improve outcomes for patients suffering from both congenital and acquired heart disease. In this talk I will discuss the application of computational fluid dynamics to the Fontan surgery, a treatment for severe congenital heart defects in which a patient is born with only one functioning ventricle. Patient specific geometric models were used to evaluate the performance of current Fontan surgical designs by quantifying fluid-mechanical efficiency under physiologic conditions including rest, graded exercise, and respiration (Marsden, et. al, Ann Biomed Eng, to appear). This work inspired a new "y-graft" design of the Fontan surgery. Evaluation of the new design demonstrates improved efficiency and lower Fontan pressures. Optimization is commonly used in engineering industry for design, but neither simulation or optimization are currently used to test surgical designs in advance of trying them on patients. Optimization of new surgical designs for patient specific models such as the Fontan surgery requires methods that are appropriate for expensive fluid mechanics problems with little or no gradient information. Efficient derivative-free surrogate-based optimization methods have been previously successful in reducing aerodynamic noise generated by airfoils in turbulent flow (Marsden, et. al J Fluid Mech, to appear). A similar set of tools is now being applied to fully couple optimization algorithms with time-dependent simulations of blood flow. I will present two model problems for optimization that are representative of important cardiovascular problems, a vessel bifurcation and an end-to-side anastomosis. Next, I will discuss the application of optimization tools in future work for the design of the Fontan surgery. Finally, I will describe the potential broad impact of optimization in designing devices and surgical procedures for congenital heart disease, coronary artery disease, and peripheral vascular disease.Location: Grace Ford Salvatori Hall (GFS), Room 107
Audiences: Everyone Is Invited
Contact: April Mundy
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Chemical Kinetic Modeling of Alkane Ignition
Wed, Nov 29, 2006 @ 03:30 PM - 04:30 PM
Aerospace and Mechanical Engineering
Conferences, Lectures, & Seminars
Tim BarckholtzExxonMobil Research and EngineeringFairfax, VirginiaThis talk will summarize work on extending high temperature kinetic models to lower temperatures, for which the ignition process is significantly different than that at high temperatures. A single, unified model has been constructed for the combustion of all alkane isomers from CH4 through C5H12 as well as for n C6H14, n C7H16, and iso C8H18. A variety of techniques were used in the assembly of the model. Sophisticated ab initio calculations were employed for the prediction of the isomerization rates of peroxy radicals; abstraction rates were generated by using linear free-energy relationships; and many rates were derived empirically or semi-empirically. The complete, pressure-dependent model has over 700 chemical species and 11,000 reactions. The performance of the model is quite good with respect to the prediction of ignition delays in rapid compression machines and other experimental devices. Finally, a methodology for the drastic reduction of reacting species in this model will be summarized, in which the sub-model for n-heptane can be reduced from approximately 250 species to less than 40 for use in CFD codes.
Location: Stauffer Science Lecture Hall, SLH, Room 100
Audiences: Everyone Is Invited
Contact: April Mundy