Department of
Mechanical and Aerospace Engineering
Abstracts 2001 - 2002
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Wednesday, July 10, 2002
1:30 p.m.
479 EBU-II
Dr. Timothy
Corrigan
"Field Emission Properties and Characterization of
Ultrananocrystalline Diamond Thin Films"
Electron field emission from diamond has received much interest for potential replacement of active matrix liquid crystal displays. CVD diamond thin films have been shown to emit electrons at much lower fields than other typical materials, and is relatively easy to fabricate. For field emission displays to be practical, they must have a low required field for emission, have uniform emission properties, and have the ability to integrate with an inexpensive process for manufacturing. This presentation reports on the growth and characterization of Ultrananocrystalline diamond (UNCD) thin films for field emission applications. First, the improvement of field emission properties of UNCD grown with the addition of nitrogen in the feed gas of the plasma gas chemistry will be discussed. Secondly, it will be demonstrated how UNCD is particularly suited to coat silicon field emitter arrays for improved field emission. Finally, the different growth mechanism behind UNCD from conventionally grown CVD diamond films make growth at temperatures low enough to integrate with glass substrates possible, and work in this area will be presented.
Dr. Timothy D. Corrigan received his Ph. D. from Northwestern University in Materials Science and Engineering. He did research at Argonne National Laboratory in the area of field emission from ultrananocrystalline diamond thin films, where he worked on improving field emission from flat films, coating Si tips on a micro scale, and on some novel designs for other structures for field emission displays. Most recently, Dr. Corrigan has worked at Intel as a senior process engineer, and has worked on improving the defect counts and throughput time from high-density plasma CVD for the flash memory process and received the Intel team award for improving quality. Dr. Corrigan served as the president of the student chapter of MRS at Northwestern University.
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Tuesday, July 9, 2002
11:00 a.m.
479 EBU-II
Dr. Mu Chiao
University of California Berkeley
"MEMS
Packaging by RTP (Rapid Thermal Processing) and Miniaturized Microbial Fuel
Cells"
Three topics will be covered in the presentation.
1) MEMS hermetic/vacuum packaging by RTP (Rapid Thermal Processing)
Hermetic/vacuum packaging is a key for resonance-base micro devices to ensure the device reliability and performance. This talk will detail a packaging scheme for micro resonators by using RTP aluminum-to-nitride bonding. The reliability and long-term testing results of the package quality will also be presented.
2) Post-packaging tuning of microresonators by PLD (Pulsed Laser Deposition)
Due to variations in the microfabrication processes, it is difficult to control the dynamic characteristics of MEMS resonators. A new approach of the natural frequency tuning for micro resonators by using a post-packaging PLD process will be described. The tuning process and measurement results will be presented.
3) Miniaturized microbial fuel cells for MEMS
A portable power source for MEMS is important for the commercialization of MEMS products. In this project, the metabolism of microorganisms (Saccharomyces cerevisiae) is used to generate electricity due to the biochemical-electrical effects. Bulk micromachining technique is used to build silicon-based microbial fuel cells. The fabrication processes and biochemical-to-electrical energy conversion characteristics will be detailed in the presentation.
Dr. Chiao recently received his Ph.D. in Mechanical Engineering from UC Berkeley. His Ph.D. work focused on MEMS, MEMS packaging and BioMEMS fuel cells; he specializes in MEMS design, fabrication and vacuum packaging, FEM analysis, thermal analysis, reliability engineering and micro fuel cells.
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Friday, June 14, 2002
1:00 p.m.
479 EBU-II
Dr. Prabhakar Bandaru
Electrical
Engineering Department
University of
California Los Angeles
"Novel Magnetic and
Semiconductor Materials with Applications to MEMS/NEMS"
The field of MEMS( Micro - Electro Mechanical Systems) and NEMS (Nano-Electro mechanical Systems) is on the verge of explosive growth, motivated by optical, sensor and biological applications. The drivers are new materials and sophisticated processing, such as electron-beam lithography. I will talk about two issues: magnetic thin film stability and semiconductor processing, with an eye on micro-/nano-systems applications.
MnBi traditionally has been used for magneto-optic storage. However, its high perpendicular anisotropy and magetostriction makes it a viable candidate for MEMS applications. It will be shown how materials physics and chemistry were used to solve a deleterious phase transformation problem, and thus stabilize MnBi thin films.
There has been a recent trend towards the development of nano-electro mechanical systems (NEMS), such as biological nanomotors. At this level of miniaturization (~ 100 nm), new physical effects and material defects will likely be a limiting factor in device performance. Studies of quantum wires in InP and GaAs based semiconductors indicate new methods of probing single defects and the importance of surface passivation. Integration of new materials onto currently used Si based MEMS devices will be discussed, keeping in mind practical materials related issues such as thin film stress and materials compatibility. In conclusion, I will outline possible future directions such as photonic crystal based MEMS.
Dr. Bandaru earned his Ph.D. in Materials Science from the University of California, Berkeley in 1998. After working for two years at Applied Materials, Santa Clara, he joined UCLA as a postdoctoral fellow. Currently, his main interests are in materials processing, heterogeneous materials integration and investigating the electronic, magnetic and optical properties of thin films for application to novel MEMS (Micro-Electro Mechanical Systems) and NEMS (Nano-Electro Mechanical Systems)devices.
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Friday, June 14, 2002
11:00 a.m.
479 EBU-II
Dr. Yuan Ping
Princeton Plasma
Physics Laboratory
"Soft
X-ray Lasers and Raman Amplification in Plasmas"
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Wednesday, June
12, 2002
11:00 a.m.
479 EBU-II
Dr. Hantao Ji
Princeton Plasma
Physics Laboratory
"Laboratory
Study of Plasma Astrophysics:
Magnetic
Reconnection and Magneto-Rotational Instability "
Many important elementary processes in space and astrophysical plasmas can be studied in laboratory. Often, these processes are also closely related to phenomena observed in fusion plasmas. Dedicated and controlled experiments not only can bring about better understanding of these processes but also can lead to new ideas for plasma confinement. This talk will focus on two such example processes: magnetic reconnection and magneto-rotational instability.
Magnetic reconnection is believed to play
essential roles in coronal activities on stars and accretion disks,
magnetospheric disturbances, and relaxation phenomena in fusion plasmas. Many important questions still remain
unanswered five decades after its initial identification in the solar
flares. A laboratory experiment, MRX
(Magnetic Reconnection Experiment), is dedicated to study reconnection physics
in controlled manners. Many import
findings include (1) the measured reconnection rates agree excellently with a
generalized classical theory, (2) resistivity is classical at high
collisionality but is enhanced at low collisionality, (3) strong non-classical
ion heating (4) and lower-hybrid fluctuations are observed. Implication of these results to
understanding reconnection and development of new ideas for plasma confinement
will be discussed.
The second example concerns angular momentum transport in accretion disks, which exist during processes of star formation, mass transfer in binary stars, and mass accretion in quasars. Search for mechanisms of fast angular momentum transport during the past three decades could not lead to a satisfactory candidate until the rediscovery of magneto-rotational instability or MRI, which is a vivid example of importance of magnetic field. A rotating gallium disk experiment has been proposed in order to realize and study MRI in laboratory for the first time, aided by stability analysis and MHD simulations. Results from a prototype water disk experiment and its close relations with angular momentum transport and relaxation phenomena will be presented.
Dr. Hantao Ji received his
Ph.D. degree in physics from University of Tokyo in 1990. He spent two years at the National Institute
for Fusion Science (NIFS) in Japan and 2.5 years at University of
Wisconsin-Madison before joining the Princeton Plasma Physics Laboratory (PPPL)
as Research Physicist in 1995. He is a
member of APS, AGU, and AAAS, and has served on various panels and
committees. He has published more than
50 refereed research papers, primarily on laboratory studies of space and
astrophysical plasmas.
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Tuesday, June 11, 2002
3:00 p.m.
479 EBU-II
Professor Patricia
J. Culligan
Department of
Civil and Environmental Engineering
Massachusetts
Institute of Technology
"Air-Flow Mechanisms During Air-Sparging Operations"
Insitu air sparging (IAS) is a technology that is used to remediate soil and groundwater contaminated with volatile non-aqueous phase liquids. During IAS, air (or another gas) is injected into an aquifer below the zone of contamination. As the air travels upward through the aquifer, contaminants in the zone of influence of the air plume are removed through volatilization and/or aerobic biodegradation. Because of its low cost, efficiency and apparent effectiveness, IAS has become very popular in the United States. Nonetheless, and despite this fact, understanding of the factors influencing IAS behavior remains incomplete. For this reason, systematic guidelines for the efficient design of IAS systems are not yet in place.
The efficiency of IAS technology is dependent on the shape of the injected air plumes. Thus, an essential factor in the production of IAS design guidelines is the development of models that can be used for predicting plume shapes. This seminar will discuss research that used the experimental technique of geotechnical centrifuge testing to examine the characteristics of an air-plume formed in a saturated medium above an injection (sparge) point. During the seminar, data from the experiments will be used to illustrate mechanisms for air-flow in saturated porous media. A new theoretical model for predicating the shape of an air-plume above a sparge point, which arose as a result of the experimental work, will then be presented. Unlike other models in the literature, this model assumes that the hydrostatic pressure at the sparge point, and not pore-scale capillary forces, dominate the air plume formation. Good agreement between the new model and the experimental data will be used to argue the validity of this assumption. The seminar will end with some proposed guidelines for IAS system design that arose as a result of this work.
Dr. Culligan received her B.Sc. degree from the University of Leeds and her M.Phil. and Ph.D. degrees from Cambridge University, England. She is Associate Professor of Civil and Environmental engineering at the Massachusetts Institute of Technology. Her research interests are in the field of geo-environmental engineering and focus primarily on the experimental and numerical modeling of flow and contaminant transport processes in geologic systems. Her current research addresses the effectiveness of in situ remediation strategies for the cleanup of waste sites. In addition, she has worked in the design of land-based disposal cells. Dr. Culligan has received numerous awards including the Arthur C. Smith Award for Under-graduate Service and the NSF CAREER Award. She is also the author or co-author of 50 journal articles, book chapters, and refereed conference papers.
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Monday, June 10, 2002
11:00 a.m.
479 EBU-II
Dr. Karl
Krushelnick
Blackett
Laboratory
Imperial College,
London
"Magnetic fields and
energetic ion production
from intense laser
interactions with solid targets"
The interaction of ultra-high intensity laser pulses with solid density plasmas has been investigated using the 100 TW beamline of the VULCAN laser system at the Rutherford Appleton Laboratory in the UK. Harmonics of the laser frequency (up to the 75th order) can be observed from such interactions. Using polarimetric measurements of the lower order harmonics we have measured that magnetic fields greater than 300 MGauss can be generated in these plasmas. Recent measurements of energetic proton beam production from laser interactions with thin solid targets will also be presented.
Karl Krushelnick was born in Woodstock Ontario, Canada and graduated with a BSc. from the University of Western Ontario in 1987. He obtained his Ph.D. in plasma physics from Princeton University in 1994. He was employed as a postdoc by Cornell University from 1993 until 1997 to do research at the US Naval Research Laboratory in Washington DC on high intensity laser plasma interactions. Since 1997 he has been with the Department of Physics at Imperial College (University of London, UK) where he is presently a senior lecturer.
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Friday, June 7,
2002
3:00 p.m.
479 EBU-II
Dr. Petra
Kastner-Klein
School of Civil Engineering and Environmental Science
University of
Oklahoma
"Mean
Flow and Turbulence Characteristics in the Urban Surface Layer"
The
seminar focuses on turbulence observations and parameterizations in the lower
part of the urban boundary layer, the so-called urban surface layer (USL). The turbulence structure in the USL
is of particular interest for air pollution modeling, since most of present air
pollution problems occur in urban areas and are related to near ground
emissions. In urban-scale dispersion
models, the USL is often represented using surface layer similarity
parameterizations. The urban effects
are taken into account by changes of surface roughness and heat flux. Strictly
speaking, boundary layer formulations of this type are only applicable in a
constant flux layer (also known as inertial sublayer) that is characteristic
for the surface layer over flat terrain with relatively
small, homogeneously distributed roughness elements. The flow structure in the USL is much more complex and
strongly influenced by the geometry and arrangement of buildings in the
underlying urban landscape. A constant
flux layer can be observed only well above the building tops, but not in the
so-called roughness sublayer (RSL) - the flow region in the immediate vicinity
of the urban canopy elements. Full-scale as well as wind-tunnel measurements indicate that
one of the characteristic features of the roughness
sublayer is an increase in the absolute values of turbulent shear stress from
essentially zero inside the urban canopy up to a maximum value, which is
typically observed at about two times the average building height. Parameterizations for such type of shear
stress characteristics inside the RSL will be presented and the consequences
for scaling of mean wind profile and turbulence statistics inside the RSL will
be discussed. The findings will be
compared with homogeneous-surface-layer assumptions and similarities between
flow in the USL and flow above vegetative canopies will be addressed.
Dr. Petra Kastner Klein earned her BS and MS in Physics and her Ph.D.degree in Civil Engineering at the University of Karlsruhe in Germany. From 1999-2000, she was a Post-Doctoral Research Associate at the Institute for Climate Research at the Swiss Federal Institute of Technology (ETH), and was appointed Visiting Assistant Professor at the University of Oklahoma in 2001. Her general areas of research interests are in atmospheric boundary layers and air pollution studies; of particular interest are flow and turbulence characteristics in urban areas, modeling of atmospheric dispersion processes, and wind tunnel modeling of geophysical flow phenomena.
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Friday, June 7,
2002
1:00 p.m.
479 EBU-II
Dr. Farhat Nadeem
Beg
Blackett Laboratory
Imperial College, London
"Wire Z-pinches"
The wire Z-pinch generates very high energy density and emits very intense x-rays. This bright source of x-rays has applications in inertial confinement fusion, radiation physics, equation of state and in industry. Numerous wire z-pinch configurations have been investigated from the simple single wire to complex multiple wire arrays. This research dates back to 1950’s with investigations of the wire fuse. With the development of pulsed sources capable of large current and fast rise time in 1970’s, there has been tremendous growth in wire z-pinches. The talk will review various z-pinch configurations.
Dr. Beg earned his B.Sc. and M.Sc. degrees from Punjab University and Quaid-I-Azam University in Pakistan, and completed his Ph.D. at Imperial College, University of London. Since 1996, he has been Research Associate in the Plasma Physics Group at the Blackett Laboratory, Imperial College. His expertise is on the experimental study of intense short pulse laser-solid interactions and various fibre z-pinch configurations. He has also studied tabletop x-ray and neutron sources for applications in medical sciences and industry.
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Thursday, June 6,
2002
1:30 p.m.
479 EBU-II
Dr. Alexandria
Boehm
Department of Chemical Engineering and Materials Science
University of California Irvine
"Coastal Water
Quality in Northern Orange County, California, USA: Sources, transport and
transformation of fecal indicator bacteria"
Surf zone water quality in northern Orange County, California, USA, varies over time scales that span at least seven orders of magnitude, from minutes to decades. Sources of this variability include historical changes in treatment and disposal of wastewater and dry weather runoff, seasonal variations in rainfall, spring-neap tidal cycles, sunlight-induced mortality of bacteria, and near shore mixing. The contribution of a sewage waste field that is released 7.5 km from the shoreline is evaluated as a possible source of fecal indicator bacteria to bathing waters in light of recent evidence of internal tides and motions on the coastal shelf. This work calls into question current bathing water regulations and also presents new tools for coastal managers to identify sources of pollution and forecast surf zone water quality.
Alexandria grew up in Kailua Hawaii. She received her B.S. in Engineering and Applied Science with Honors from California Institute of Technology in 1996. While there, she did research with Mary Lidstrom and Michael Hoffmann. Alexandria also spent a summer at the University of Hawaii doing research on population dynamics of Prochlorococcus in Kaneohe Bay with Michael Landry. She received her M.S. and Ph.D. from University of California Irvine in 1997 and 2000, respectively, in environmental engineering. Her thesis work focused on understanding the fate of water-borne particles. She is currently a faculty fellow at UCI in the Department of Chemical Engineering and Materials Science where she teaches thermodynamics, fluid mechanics, and pollution control, and also conducts research on factors that influence coastal water quality.
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Tuesday, June 4, 2002
1:00 p.m.
479 EBU-II
Dr. Scott
Socolofsky
Institute for
Hydromechanics, University of Karlsruhe
" Large Coherent
Structures in Shallow Turbulent Flow:
experiments and numerical stability
analysis"
Shallow flows are ubiquitous in nature, ranging from
river, estuarine, and oceanic flows to stratified flows in the atmosphere. Although turbulent eddy size is typically
limited to the shortest dimension (in this case the depth), large-scale
coherent turbulent structures are observed in shallow flows with length-scales
orders of magnitude greater than the depth.
These structures are sometimes treated as so-called two-dimensional
turbulence.
Our research at IfH includes both experimental and analytical work, focused lately on the stability of turbulent wakes behind islands in shallow water flow. The laboratory experiments include Laser Doppler Velocimetry measures of the turbulent flow characteristics coupled with Laser Induced Fluorescence (LIF) to understand the short time- and space-scale turbulent transport characteristics of the flow. Laboratory experiments also include Particle Image Velocimetry coupled with Planar Concentration Measurements to study the basin-scale transport characteristics of the large coherent structures. These laboratory data are also used to interpret numerical work focused on the stability of these shallow wakes. The different stability regimes determine the fashion in which these large-scale structures detach from the island; thus, they determine the nature of the turbulent transport.
Dr.
Scott Socolofsky earned his MS (1997) and Ph.D. (2001) degrees at the
Massachusetts Institute of Technology in Civil and Environmental
Engineering. His research topics were bacteria transport in the
Charles River watershed (M.S. thesis) and laboratory experiments on multi-phase
plumes in stratification and crossflow (Ph.D. thesis). Since finishing his Ph.D., he has been
working as a research associate at the Institute for Hydromechanics (IfH) at
the University of Karlsruhe, Germany, on the stability of shallow turbulent
wakes. This year he was promoted to the
position of Division Head for Environmental Fluid Mechanics at the Institute
for Hydromechanics.
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Thursday, May 30, 2002
2:00 p.m.
479 EBU-II
Charles Wang
President, Optodyne,
Incorporated
Compton California
"A New Laser 3D
Measurement Technique
and its Impact on Machine Positioning Accuracy"
Competitions in global manufacturing today require higher accuracy and
better quality machines. To achieve
higher positioning accuracy, it is important to measure the 3-dimensional or
volumetric positioning errors and compensate the errors. Conventional laser interferometers may take
several days to measure these errors.
Optodyne invents a new laser vector or 3D measurement technique. This new laser measurement technique can
measure the volumetric positioning errors, including 3 displacement errors, 6
straightness errors and 3 squareness errors, in a few hours instead of a few
days. The laser vector measurement
technique is a major breakthrough in laser dimensional measurement. The basic theory, the experimental verification
and its applications will be discussed.
Its impact on the machine tool positioning accuracy, quality and
productivity will also be discussed.
Charles Wang is President of Optodyne, Inc, a manufacturer of laser
measurement instrument. He received a B.S. degree in Mechanical Engineering
from National Taiwan University in 1959 and M.S. and Ph.D. degrees in
Aeronautics from California Institute of Technology in 1963 and 1967,
respectively. His Ph.D. dissertation
was in the field of high-temperature gas dynamics and plasma physics.
In 1969, Dr. Wang did research work on laser development and
application in the Department of Applied Mechanics and Engineering Sciences
(AMES) at UCSD. He was an Adjunct
Professor from 1979-90 and taught advanced fluid mechanics, laser development
and applications. He was a Senior
Scientist of Aerospace Corporation from 1976-86 and has been President of
Optodyne, Inc since 1986. He has more
than 100 publications and inventions.
He was president of the Chinese American Engineers and Scientists
Association of Southern California from 1979-81, program chairman of the
International Conference on Lasers 1979-80, and editor in chief of the Series
in Laser Technology 1983-91. He is a
fellow of the Optical Society of American, associate fellow of American
Institute of Aeronautics and Astronautics and member of many professional and
honorary societies. He is also listed
in the Who’s Who in America.
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Wednesday, May 22, 2002
11:00 a.m.
479 EBU-II
Dr. D.G. Whyte
Fusion Energy
Research Program
University of
California, San Diego
"Mitigation
of Disruption Damage Using High Pressure Noble Gas Injection"
As tokamak
fusion research approaches the realization of burning plasmas it will be
necessary to develop methods to avoid or control the damage caused by
disruptions. In-vessel components of
the tokamak are damaged in three principal ways: divertor surface
melting/ablation by plasma heating, mechanical stresses caused by poloidal halo
currents, and the amplification of runaway relativistic electrons that
eventually are lost into, and damage the wall.
The magnitude of the disruption damage increases with the plasma energy
density; in future burning plasma experiments the damage caused by a single
disruption may necessitate the halt of further operation.
Experiments on the DIII-D tokamak have demonstrated a technique that mitigates the three disruption damage effects. A high-pressure jet of a noble gas (neon or argon) is injected into the plasma. The jet is found to penetrate to the central plasma at the gas sound speed (300-500 m/s), seemingly due the high ram pressure of the gas jet. The plasma energy is dissipated uniformly by UV radiation from the injected impurity species over the entire wall. The radiative collapse initiates a rapid current quench with the plasma remaining well centered in the vessel, effectively reducing halo currents. Runaway electrons are controlled on DIII-D by the large density of bound electrons in the plasma volume, despite the large parallel electric field caused by the cold plasma.
Physical models have been developed to understand and extrapolate the DIII-D results. In applying the models to burning plasma experiments we find that thermal and halo current mitigation is possible and that runaway electrons can be suppressed.
Dr. Whyte earned his B.S. degree in Engineering Physics from the University of Saskatchewan and his Ph.D. from the University of Quebec in Montreal. He became a Postdoctoral Fellow at the DIII-D National Fusion facility at General Atomics in San Diego in 1993 and coordinator of the Divertor Material Evaluation Studies (DiMES) program on DIII-D in 1995. In 1997 he joined UCSD as Research Scientist, continuing his research on DiMES on DIII-D as well as plasma-surface interactions on the PISCES facility at UCSD. In parallel, he began work on mitigating the wall damage effects caused by disruptions. He has published 96 peer-reviewed publications.
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Tuesday, May 21, 2002
1:00 p.m.
479 EBU-II
Mr. Prakash Bhave
Department of Environmental Science and Engineering
California Institute of Technology
"Air
Pollution at the Single Particle Level:
Integration of
Model Predictions and Measurements"
Particulate air pollution is of growing concern in the United States and around the world. Elevated concentrations of aerosols (solid particles and liquid droplets suspended in air) correlate with increased rates of lung cancer, cardiopulmonary disorders, and human mortality. A detailed understanding of the size, chemical composition, and concentration of atmospheric particles is needed to assess their effects on human health, as well as on regional visibility and global climate. One can acquire such knowledge through direct measurements of ambient aerosols, or by utilizing mathematical air quality models. New and innovative instruments permit measurements of the size and composition of individual particles,
rather than inferring aerosol properties from bulk particulate matter samples. Concurrently, our research group has developed an air quality model that numerically simulates the emissions of discrete particles, and their transport and chemical evolution in the atmosphere.
This presentation will focus on how we can integrate and compare the measurements taken by state-of-the-science single particle instruments, with predictions made by state-of-the-science mathematical models. This is a challenging task, but ultimately can provide tremendous value to policy makers who are seeking least-cost solutions to urban and regional air pollution problems. Comparisons of single particle measurements and model predictions will be presented. Efforts to quantify the single particle Chemical composition measurements will also be described. Applications of the model and measurement combination will be discussed, with the end goal of reducing particulate pollution in the air we breathe.
Prakash Bhave received a Bachelor of Science degree in Environmental Engineering from UC Berkeley in 1998, and a Masters of Science degree in Environmental Engineering from Caltech in 1999. He is currently completing his doctoral research as a visiting scientist in the School of Earth and Atmospheric Sciences at the Georgia Institute of Technology.
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Friday, May 17,
2002
11:00 a.m.
479 EBU-II
Ms. Linsey C. Marr
Department of Civil and Environmental Engineering
University of California at Berkeley
"Diurnal,
weekly, and decadal changes in photochemical air pollution"
Despite efforts to improve air quality over the past several decades, ozone remains a persistent threat to human health, agriculture, and forests. Ozone control strategies aimed at reducing precursor emissions of volatile organic compounds (VOC) and nitrogen oxides (NOx) have not always succeeded. Ambient ozone levels are higher on weekends in many areas in spite of lower precursor emissions on weekends; this phenomenon has become more widespread in California over the last twenty years. Improved estimates of motor vehicle emissions are developed for use in an Eulerian photochemical airshed model; the modeling system is used to examine the effects of changes in the mass and timing of motor vehicle emissions on weekend ozone formation. Results show that the primary cause of the weekend effect is the large decrease in NOx emissions due to much lower diesel truck traffic on weekends. Areas where ozone formation is VOC-sensitive can therefore expect to experience higher ozone concentrations on weekends. Day-of-week differences in the diurnal timing of motor vehicle emissions have a much smaller effect on ozone formation.
Modeled ozone concentrations using emission inventories for 1990 and 2000 are also compared to determine how changes in emissions have affected ambient air quality over the past decade. Long-term changes in the emission inventory have produced a shift towards greater VOC-sensitivity, and the weekend ozone effect has grown more prevalent because diesel trucks now account for a larger fraction of total NOx emissions. Results suggest that the presence of higher ozone on weekends can be used as an indicator of VOC-sensitivity in an area.
Linsey Marr is a graduate student studying air quality engineering at UC Berkeley; she will be receiving her Ph.D. in Environmental Engineering from UC Berkeley in May 2002. She earned her B.S. in Engineering Sciences from Harvard College in 1996. She has also been a visiting scientist at the National Center for Atmospheric Research.
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Monday, March 25,
2002
11:00 a.m.
479 EBU-II
Dr. David M. Lynn
Department of Chemical Engineering
Massachusetts Institute of Technology
"Synthesis and
Discovery of New Polymeric Materials or Gene Delivery"
The safe and efficient delivery of therapeutic DNA to cells represents a fundamental obstacle to the clinical success of gene therapy. The challenges facing synthetic delivery vectors are particularly clear, as both cationic polymers and liposomes are less effective at mediating gene transfer than viral vectors. Although the incorporation of new design criteria has led to advances toward functional delivery systems, the paradigm for the development of polymeric vectors remains the incorporation of design elements into new materials as part of an iterative, linear process. We have applied a parallel strategy for the synthesis of libraries of degradable cationic polymers to the discovery of new synthetic vector families. Feasibility studies have centered on the synthesis, evaluation, and rapid cell-based screening of a library of 140 degradable polymers. The incorporation of robotic strategies or automation and miniaturization could significantly accelerate the pace at which new DNA-complexing materials and competent transfection vectors are identified.
Dr. Lynn earned his Ph.D. in organic chemistry from Caltech in 1999. He has since been a NIH Postdoctoral Fellow in the Department of Chemical Engineering at MIT, conducting research in the development of new synthetic materials for gene delivery. Specifically, he has developed new degradable polycations as alternatives to viruses for the safe and efficient delivery of therapeutic DNA to cells. His research interests are situated at the interface of chemistry, biology and materials science.
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Thursday, March 7, 2002
2:00 p.m.
479 EBU-II
Professor Thomas
J.R. Hughes
Division of
Mechanics and Computation
Department of Mechanical Engineering
Stanford University
"Multiscale Methods in
Turbulence: A Variational Approach to Large Eddy Simulation"
Calculating turbulent flows requires solution of the Navier-Stokes equations at high Reynolds numbers. This is referred to as Direct Numerical Simulation (DNS). However, it is currently not feasible to perform DNS for all but the simplest turbulent flows due to prohibitive computational requirements. Even if current rates of increase of computational power continue, it is unlikely DNS will become an everyday engineering tool in this century! The problem stems from the fact that turbulence is characterized by a very broad spectrum of spatial and temporal scales and although engineering interest is focused on the behavior of the larger scales their dynamics is influenced by the presence of small scales due to nonlinear interactions.
Large Eddy Simulation (LES) is a procedure in which only larger scales are resolved numerically, and effects of smaller scales are modeled. This reduces computational requirements significantly and currently enables solution of many physically interesting flows. Recently, LES has become an important engineering tool. Even with LES, turbulent calculations still require enormous computational resources but there is hope that through continued improvements in computer performance and modeling concepts LES will emerge as the standard technology for computing flows of engineering interest.
The devil is in the details: There is still no general agreement as to best modeling procedures within LES, and even the proper theoretical framework of LES is debated. The presentation begins with a brief overview of traditional LES concepts and identified points of concern. Elementary modeling ideas are reviewed and examined from numerical analysis and “spectral eddy viscosity” points of view. The variational multiscale formulation of the Navier-Stokes equations is proposed. It has features that obviate some of the criticisms of the classical LES formulation and provides a framework with potential for improved modeling. Computations employing the simplest instantiations of the ideas are presented for homogeneous isotropic flows and channel flows, and in all cases very good results are obtained. Particular accuracy is noted for non-equilibrium flows.
Professor Hughes earned his B.S. at the Pratt Institute and his Ph.D. from UC Berkeley. He is a fellow of the American Academy of Mechanics (AAM), the American Society of Mechanical Engineers (ASME), the U.S. Association for Computational Mechanics (USACM), the International Association for Computational Mechanics (IACM) and the American Association for the Advancement of Science (AAAS). He has received numerous awards from such societies as ASCE, ASME, USACM, and IACM in addition to the Computational Mechanics Award from the Japan Society of Mechanical Engineers. His research interests are in computational methods in solid, structural and fluid mechanics. He has published over 300 works on computational mechanics and is a member of the National Academy of Engineering.
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Monday,
December 3, 2001
11:00 a.m.
479 EBU-II
Dr. Sungho Jin
Agere Systems/Lucent Technologies (Bell Labs)
"Materials, Structure and Applications of some Advanced
MEMS Devices"
Since the famous lectures by Richard Feynman, “There is Plenty Room at the Bottom” in 1959 and “Infinitesimal Machinery” in 1983, the drive toward nano- and micro-materials and devices has been one of the most fascinating scientific and technological goals. The MEMS technology owes much of its base to modern silicon fabrication and lithography processes. The design of standard MEMS device and fabrication can relatively easily be accessed these days by utilizing commercially available MEMS foundries. However, MEMS with differential advantages such as new capabilities, advanced functionalities, improved reliability, and valuable intellectual properties may more readily be obtained, not with standard foundry MEMS, but with truly unique designs/processes or by incorporating new/advanced materials, for example, nano materials or active functional materials.
In this presentation, I will describe some unique approaches and experiences that we have had in recent years related to the advanced materials, design of MEMS structures, their characteristics and potential applications of electron-emitting MEMS, optical MEMS, RF micro-switch MEMS, and bioMEMS. Careful considerations of mechanical and stress behavior, thermal, electrical, magnetic, chemical and metallurgical properties are needed to ensure high performance of the devices. The R&D and applications of these MEMS devices require intimate interdisciplinary collaborations among scientists in many different fields, which makes it all the more exciting and challenging.
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Friday, October
12, 2001
2:00 p.m.
479 EBU-II
Professor Farhang Shadman
Department of Chemical and Environmental Engineering
The University of Arizona
" Challenges in the Application of New Materials for Future
Semiconductor Processing "
During the last two decades, the
semiconductor industry has enjoyed unprecedented growth due to its success in
continuously improving the computing power per unit chip area. This growth, illustrated by Moore’s law, has
been primarily through innovations in scaling down the device geometry using
silicon-based materials. The strategy
of squeezing every drop of performance out of conventional materials is rapidly
approaching its limits. Therefore, new
materials, and more importantly new materials- processing techniques, are
needed to continue the trend for better, faster, and cheaper devices. This presentation will cover some examples
of the challenges in this area. In
particular, issues related to thin dielectric films and their fabrication
requirements will be discussed. Recent
results on the role of interfacial contamination, particularly on characterization,
monitoring, and control of contaminants, will be presented. Other examples of the development of
advanced thin-film membranes for ultra-purification of fluids used in
semiconductor industry will be briefly discussed.
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Information: (858) 534-0113