MECHANICAL ENGINEERING DEPARTMENT SEMINARS

Fall Seminar Series 2004

Fridays 2:30-3:30 PM, Room: 3-370

 

 

September 10

 

 

MEMS-Based High Power Chemical lasers

 

 

Abstract: Chemical lasers offer several key advantages for metal cutting, drilling, and welding, including high power, short wavelength, and small spot size. However, the use of conventional chemical lasers has been limited, in part because they require bulky hardware and use reactants inefficiently. Replacing the macroscale components of a chemical laser with arrays of MEMS devices promises to reduce hardware size and dramatically improve efficiency. We have designed such a MEMS-based, high power Chemical Oxygen Iodine Laser, also called microCOIL. This talk will describe the parts and operation of a COIL laser, how its components may be improved by adapting them to the MEMS scale, and the modeling that has been used to predict the system’s performance. Schematic architectures for microCOIL systems ranging from a few kW to 100 kW will also be presented.

Short-bio: Carol Livermore is an Assistant Professor in the Department of Mechanical Engineering at MIT. She received her B.S. in Physics from the University of Massachusetts, Amherst in 1993, and her A.M. and Ph.D. in Physics from Harvard in 1995 and 1998 respectively. Her research focuses on the creation of high power MEMS devices, including electric generators and chemical lasers, and on the creation of self-assembly techniques for organizing complex systems at the nanoscale.

 

 

 

September 24

 

 

Making Robust Design more Effective

 

 

Abstract: Robust design is a set of techniques for making machines function more consistently despite variations in system inputs, interfaces, and operating conditions. This process tends to be resource intensive because it requires exploration of the design space and the space of uncertain parameters in the machine's environment. This presentation describes ongoing research to develop and validate robust design methods that are more effective for industry applications.

Short-Bio: Dan Frey is an Assistant Professor of Mechanical Engineering and Engineering Systems at MIT. He is interested in experiments and their role in engineering design. In his research, he develops theories and new methods for effective use of experimentation. Prof. Frey holds a Ph.D. in mechanical engineering from MIT, an MS from the University of Colorado, and a BS from RPI. Prof. Frey has earned the Baker award for undergraduate teaching (1999) and the Department of Aeronautics and Astronautics teaching award (2000).

 

 

 

October 1

 

 

From sliding paper to crawling snails:

novel applications of thin films

 

 

Abstract: Liquid thin films have long been studied in the context of industrial, biological and geophysical applications from spin coating in microcircuit fabrication to the liquid lining in the lung. In general, typical length-scales in these systems are set by surface tension. However, when the film is bounded by a flexible membrane, elasticity takes on the role of surface tension. We discuss some of the consequences of substituting elastic effects for surface tension in the context of several commonly observed phenomena, such as sliding paper and floppy drives, and in more exotic applications such as microfluidic switches and robotic snails.

Short-bio: Anette Hosoi is an Assistant Professor in the Department of Mechanical Engineering at MIT. She received her A.B. in Physics from Princeton University in 1992 and her Ph.D. in Physics from the University of Chicago in 1997. Her research interests include thin films, complex fluids, locomotion and optimization, free surfaces and fluid/structure interactions.

 

 

 

October 15

 

 

Towards a Sustainable Energy Future

 

 

Abstract: The fossil fuels era is slowly coming to an end. Dwindling resources, global warming and dependence on energy imports are calling for energy from clean domestic sources. Time has come for the establishment of a sustainable energy future. But which way shall we go.
Energy from renewable sources is abundant, but can satisfy the needs of society only if most rationally used. With the exception of biomass nature provides mainly physical energy: solar radiation, motion of wind and water, heat from the ground, all harvested as electricity. Today's chemical energy base will change to an electrical one. This involves much more than a simple replacement of gasoline by hydrogen. Chemical energy converters like heat engines and even fuel cells may become superfluous after electricity has become the base energy. Natural gas fired power plants will disappear and heat pumps will become real energy multipliers. The entire energy technology will gradually adapt to electricity. The sustainable future will be based on an "electron economy".
Chemical energy carriers have to be synthesized from biomass or electricity. Synthetic liquid fuels, not hydrogen will be derived from biomass. Hydrogen has to be produced by water electrolysis. But too much energy is lost by converting renewable electricity into hydrogen, packaging the gas by compression or liquefaction, transport the energy commodity to the user and converting it back to electricity by fuel cells. Distributed as hydrogen, not more than 25% of the original energy will be available to the energy user while 90% may reach the destination via existing power lines. As a consequence, hydrogen electricity will be four times more expensive than power from the grid. People will improve the thermal standards of their homes and switch to electricity, or use electric cars for the daily drive to work. Hydrogen energy can never compete with its electrical source energy. There is no room for a hydrogen economy in a sustainable energy future.

Short-bio: Diploma Degree in Aerodynamics (ETH Zurich), PhD in Engineering (UC Berkeley), Assistant Professor at Syracuse University, Head of the Free Molecular Flow Division at the DLR in Germany. Co-founder and first president of the German Solar Energy Society (1975), fuel cell project manager at ABB Switzerland (1987), freelance fuel cell consultant since 1990. Founder of the European Fuel Cell Forum and organizer of the Lucerne Fuel Cell Forum, an international annual event of highest reputation. Since 1973 Ulf Bossel has been one of Europe's leading figures in the renewable energy debate.

 

 

 

October 22

 

 

Detection and Real Time Processing of Odor Plume

Information by Arthropods in Air and Water

 

 

Abstract: Many arthropods detect odors by means of antennae attached to their heads. Examples include insects (moths) which are primarily land-based animals living in an aerobic environment, and crustaceans (crayfish and lobsters) which live in an aquatic environment. The odor plumes may consist of, for example, pheromones originating from a female moth to attract male moths, or from decomposing organic matter that feeds a lobster. The process of odor detection is multiscale, ranging from hundreds of meters associated with plume dispersal phenomena to the nanometer scale chemo-receptor pore sites on the sensilla. While much is known about the characteristics of plumes, antennae, sensilla and the receptor pores in their respective scale ranges, comparatively less has been said about the overlap between adjacent ranges where the “information transfer” affecting behavior takes place. The speaker will present and discuss a multi-scale physical-chemical model for odor plume detection applicable to moths in air or crayfish in water. In the case of moths, odor-elicited anemotactic behavior will be explained.

Short-bio: Joseph A.C. Humphrey is a Wade Professor of Engineering and Chair of the Department of Mechanical and Aerospace Engineering at the University of Virginia. Professor Humphrey holds a PhD. from the University of London and M.Sc from the University of Toronto. He has been a recipient of Nancy and Neal Wade Professor of Engineering and Applied Science, University of Virginia (2000) and is a Fellow of the American Society of Mechanical Engineers (1993). He is listed in the Who's Who of Science and Engineering (1991-) and Who's Who in the World (1995-). He has over 120 archive journal and 90 conference papers on government/industry-funded experimental and theoretical investigations of flow, heat and mass transfer phenomena: application of laser-Doppler velocimetry and flow visualization techniques; computational fluid mechanics; turbulence modeling; buoyancy-, curvature-, and rotation- driven instabilities and transition to turbulence.


 

 

 

October 29

 

 

Engineering Design: The View from Mars

 

 

Abstract: Engineering design presents many challenges, both immediate (e.g., How can a desired function be provided within the power, volume and mass constraints) and deep (e.g., Is design fundamentally informal in nature, or is there underlying structure to the process. How much modularity is beneficial in designs). Nowhere are these many challenges more urgently apparent than in the design of interplanetary exploration spacecraft. In this environment, there are not only all of the challenges of design for terrestrial operation, but additionally our knowledge of the environment in which the spacecraft perform is incomplete, and the ability to prototype and test is extremely limited. The full slate of unknowns (as with any design) is complicated by "unknown unknowns": those hazardous conditions and failure modes that cannot be anticipated, but despite which the spacecraft must operate successfully. 
In the face of these difficulties, NASA's Jet Propulsion Laboratory has a distinguished and rich (but not unblemished) history of success, including the successful landing of the Mars Pathfinder spacecraft and Sojourner Rover on July 4, 1997, and the Mars Exploration Rovers on January 3, and January 24, 2004. The Laboratory is now well into the highly successful extended operations of the rovers. This talk will present an overview of the engineering design of the Mars Exploration Rovers, with a simulation of the mission from launch through landing and roving, and an update on the latest status on Mars.

Short-bio: Dr. Erik Antonsson is a Professor of Mechanical Engineering at theCalifornia Institute of Technology in Pasadena, CA, U.S.A Dr. Antonsson is currently on leave from Caltech serving as the Chief Technologist at NASA's Jet Propulsion Laboratory (JPL). He earned a B.S. degree in Mechanical Engineering with distinction fromCornell University in 1976, and a Ph.D. in mechanical Engineering fromMassachusetts Institute of Technology in 1982. He was an NSF Presidential Young Investigator (1986-1992), and won the 1995 Richard P. Feynman Prize for Excellence in Teaching, and is a co-winner of the 2001 TRW Distinguished Patent Award. 
Dr. Antonsson is a Fellow of the ASME and a member of the IEEE, SME, SAE, ACM, ASEE, IFSA, and NAFIPS. Dr. Antonsson is currently on the editorial board of the InternationalJournal: Research in Engineering Design, and served on theeditorial board of Fuzzy Sets and Systems from 1997 through 2004,and from 1989 to 1993 served as an Associate Technical Editor of the ASME Journal of Mechanical Design, with responsibility for the DesignResearch and the Design Theory and Methodology area. He served as the Executive Officer (Chair) of Mechanical engineering from 1998 to 2002, as a member of the Faculty Board of theCalifornia Institute of Technology (2001-2004), and as a memberof the Caltech/MIT Voting Technology Project (2001-2002). He has published over 100 scholarly papers in the engineering design research literature, has edited two books, and holds six U.S. Patents. He is a Registered Professional Engineer in California, and serves as an engineering design consultant to industry, research laboratories and tothe Intellectual Property bar.


 

 

November 5

 

 

Nanostructured Anodes and Cathodes

for Rechargeable Lithium Batteries

 

 

Abstract: There is widespread interest in if, how, and why nanostructured materials have unusual properties. We have studied the electrochemical properties of nanostructured electrodes for rechargeable batteries. Potential advantages of nanostructured materials for electrodes include an enhanced kinetics of lithium transport, minimized stress gradients in the materials, and a possible contribution of grain boundary regions to the capacity for lithium storage. Experimental results from rechargeable cells will be presented on electrodes made from many pure elements. Nanostructured group IV elements showed capacities of 2,000 mAh/g and reasonable cycle life in controlled laboratory tests. This excellent combination of capacity and cycle life is not achieved in conventional materials because of the enormous strains of lithiation. These good properties of nanostructured electrodes may originate with the smallness of the electrode dimensions compared to characteristic lengths for microstructural damage.

Short-bio: Brent Fultz is a professor at California Insititute of Technology in the Division of Engineering and Applied Science. Professor Fultz holds a Ph.D. in Engineering Science, from University of California, Berkeley. He is a recipient of Presidential Young Investigator Award. Profesor Brent Fultz and his group have been involved over the past few years, in performing an increasing number of experiments at national user facilities that supply intense photon and neutronbeams.


 

 

 

November 19
   

 

Mechanotransduction: Understanding How Cells Sense Mechanical Signals with Novel Microscopic and Spectroscopic Tools

 

Abstract: Mechanical properties of the cellular cytoskeleton play important roles in many biological processes such as signal transduction, migration, and differentiation. An understanding of these processes is required to provide insights into a variety of diseases such as cardiac hypertrophy, cancer metastasis, and embryo development. Cellular cytoskeleton is a complex mechanical system that is continuously and actively remodeled in a living cell. Our laboratory has developed a number of technologies to quantify cytoskeletal properties and signaling processes that regulate them. In this presentation, I will describe four new tools for the study of cell mechanics: temporal resolved fluorescence energy transfer microscopy, fluorescence laser tracking microrheometry, controlling cell migration by lithographic patterning, and two-photon 3D image cytometry.

Short-bio: Peter So is an associate professor at Massachusetts Institute of Technology in the Department of Mechanical Engineering and Division of Biological Engineering. Professor So holds a Ph.D. from Princeton University . His research area is primarily Fluorescence microscopy and spectroscopy instrumentations, Deep tissue imaging, Functional imaging of cellular systems, Single Protein Dynamics, Bio-micromechanics.


 

 

 

 

December 3
   

 

Elasto-Capillary Thinning and the Breakup of Complex Fluids"
(or why some things are stickier than others!)

 

Abstract: The uniaxial extensional viscosity is a fundamental material property of a fluid which characterizes the resistance of a material to stretching deformations. For microstructured fluids, this extensional viscosity is a function of both the rate of deformation and the total strain accumulated. Some of the most common manifestations of extensional viscosity effects in complex fluids are the dramatic changes they have on the lifetime of a fluid thread undergoing capillary breakup. In a pinching thread, viscous, inertial and elastic forces can all resist the effects of surface tension and control the necking that develops during the pinch-off process. The dominant balance of forces depends on the relative magnitudes of each physical effect and can be rationalized by dimensional analysis. The high strains and very large molecular deformations that are obtained near breakup can result in a sharp transition from a visco-capillary or inertio-capillary balance to an elasto-capillary balance. As a result of the absence of external forcing the dynamics of the necking process are often self-similar and observations of this self-thinning can be used to extract the transient extensional viscosity of the material. The intimate connection between the degree of strain-hardening that develops during free extensional flow and the dynamical evolution in the profile of a thin fluid thread is important in many industrial processing operations and is also manifested in heuristic concepts such as spinnability, tackiness and stringiness. Common examples encountered in every-day life include the spinning of ultra-thin filaments of silk by orb-weaving spiders, the stringiness of cheese, the drying of liquid adhesives, splatter-resistance of paints and the unexpectedly long life-time of strands of saliva.

Short-bio: Gareth McKinley is a professor at Massachusetts Insititute of Technology in the Mechanical Engineering Department. Professor McKinley holds a Ph.D. in Chemical Engineering , from M.I.T.  He is a recipient of the Frenkiel Award of the APS Division of Fluid Dynamics in 2002 and was the Technical Program Chair at the 74th Annual Meeting in the Society of Rheology in 2001. Profesor McKinley holds the position of a Director, -'Program in Polymer Science & Technology' at MIT.


 

 

 

December 10
   

 

A Low Greenhouse Gas Energy Future:
Technical Challenges to our Scientific Community

 

 

Abstract: The closing of the twentieth century has seen many decades-long scientific challenges come well into hand. Criteria pollutants from transportation sources are controlled to levels unthinkable a few decades ago. Photochemical smog is less prevalent than many would have believed possible given the growth of energy usage. And even air toxic species, the most recent of this type of challenge, appear to be coming into control. While there remains much to do to continue this trend, it can arguably be said that these battles have been hard fought, but largely won.

Unfortunately a new battle has emerged. It is the battle to combat environmental change due to carbon dioxide, a non-toxic, biologically productive, largely inert byproduct of fossil fuel usage. Of course this challenge is not really new; we have known of the greenhouse effect for decades and much study and debate has surrounded the potential of carbon dioxide to cause significant global warming. But what has perhaps not been sufficiently appreciated is the magnitude of effort required to reduce the risk of climate change. It is a problem of a scale beyond any which humankind has ever tackled.

The question is: What can be done. Answers include political, industrial, societal, and technical aspects. In this lecture an attempt is made to outline the scope and magnitude of the problem and areas where technical progress may help contribute to a solution. No attempt is made to be comprehensive, but instead a number of examples are cited where there may be the potential for our community to contribute to resolving the grand challenge of the twenty-first century.

Short-bio: Christopher Francis Edwards, an associate professor in the thermosciences division of the Department of Mechanical Engineering, has been a member of Stanford???s faculty since 1995. He is the Director of the Advanced Energy Systems Laboratory and was recently named the John Henry Samter University Fellow in Undergraduate Education.

Edwards received his masters and doctoral degrees from the University of California-Berkeley in 1982 and 1985, respectively. His research is in the area of spray dynamics and combustion, using a combination of theory and experimentation to improve our understanding of two-phase combustion systems and to generate new, more efficient and cleaner ways to generate power or achieve propulsion. His research includes the development of next-generation strategies for gas turbine and piston engines and other advanced energy systems.

Edwards has won numerous awards for teaching and research, including the Undergraduate Teaching Prize from the Stanford chapter of Phi Beta Kappa in 1999 and the Bing Fellowship for outstanding undergraduate teaching in 1998. He received the Frederick E. Terman Fellowship and the Powell Fellowship in 1997. In 1994, he won the Adams Award from Sandia National Laboratories, where he was a Distinguished Member of Technical Staff before coming to Stanford.