Students Square Off in Engineering Contest

PASADENA, Calif.-Fire up the griddle! It's time for the 20th installment of the California Institute of Technology's ME 72 Engineering Design Contest, which will be held at 2 p.m. on December 1 outside Caltech's Chandler Dining Hall. This year's theme: an "energy cook-off."

The 10 pairs of student contestants won't actually be cooking energy, of course--or even cooking with energy. Over the past 10 weeks, their challenge has been to design and manufacture a small Stirling engine--an engine that uses an externally applied fuel or heat source to drive pistons that generate power (as opposed to the internal combustion engine that propels your car). In this case, the one-foot-tall engines will suck up the heat thrown off a 300-degree Fahrenheit propane-powered portable pancake griddle wheeled out of the dining hall for the competition.

If the engines work, they'll pump out about one watt of power that will then juice up gadgets ranging from a fan to a low-wattage laser to a small light-up Christmas tree.

The students will be judged on the efficiency and speed of their engine, the creativity of its design, and its overall cost. They will also be evaluated on how well they predicted the performance of their engines.

Preparing for the contest, says ME 72 instructor Melany Hunt, a professor of mechanical engineering at Caltech, has given the students a firsthand taste of engineering in the real world. "The students have had to take their ideas from conception to completion, while taking into account all aspects of the process, including the cost and materials," Hunt says. "Plus," she adds, "they have had to adhere to a fixed timetable, which is not something Caltech students are usually very good at."

Members of the media are welcome to attend the competition. For more information, including contest rules, visit the ME 72 website at http://www.me.caltech.edu/me72/

### Contact: Kathy Svitil (626) 395-8022 ksvitil@caltech.edu Visit the Caltech Media Relations Web site at: http://pr.caltech.edu/media

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NSF Awards $11.16 Million to Caltech's Center for the Science and Engineering of Materials

PASADENA--The National Science Foundation today awarded $11.16 million to the Center for the Science and Engineering of Materials (CSEM) at the California Institute of Technology. The renewal funding will allow the center to continue its work in exotic and futuristic materials applications, such as macromolecular materials, ferroelectric photonics, novel composites of glass and metals, spintronic devices, and fuel cells.

According to Harry Atwater, director of the center and an engineering professor at Caltech, the new funding will allow 18 Caltech faculty members and numerous graduate students and postdoctoral researchers to pursue novel research programs that appear to be especially promising.

"The center has been operating since September of 2000, but the renewal procedure was highly competitive," Atwater said. 'We're delighted to receive the NSF funding."

According to Atwater, the center will focus on three major interdisciplinary areas of materials research, and will also devote resources to two "seed" projects, albeit on a smaller scale. The major interdisciplinary areas are the following:

-Macromolecular materials. One of the principal goals is to produce tailored responses to cell adhesion so that artificial implants and transplants will work better. A longstanding problem with tissue transplants is rejection by the patient's own immune system, and evidence shows that novel ways of attending to the microscopic details of cellular response could trick the immune system into thinking that the foreign body "looks" like the rest of the body at the microscopic level. Led by David Tirrell, chair of Caltech's Division of Chemistry and Chemical Engineering, the effort in cell adhesion also demonstrates the highly interdisciplinary nature of the center, because chemists, chemical engineers, biologists, engineers, and others will all be involved in the work.

-A new research emphasis for the center will be ferroelectric photonic materials. This research involves the changing of optical properties of materials used to modulate light from lasers. Normally, the optical properties of a material, such as the refractive index, cannot be tuned after fabrication-which explains why eyeglass wearers must each have their own individual prescriptions. But there are situations in which engineers would like to tune the transparency or frequency response of optical devices after fabrication by simply applying a voltage-and ferroelectric materials let you do just that. This ability to harness and tune optical properties after fabrication will open up such applications as tunable microdevices for "photonic integrated circuits" that would lead to much greater compactness, lower power demands, and lower costs. This area of the center is led by Kaushik Bhattacharya, professor of mechanics and materials science.

-The third area, bulk materials and composites, is carried over from the center's beginnings in 2000. Led by Bill Johnson, the Mettler Professor of Engineering and Applied Science, the effort will focus on the fabrication processes that could combine liquid and glassy metals (i.e., materials with no crystalline structure) with nanoscale crystals to exploit the unique mechanical attributes of each. The researchers think they may succeed in creating a tough and ductile structural metal which has two to three times the strength of steel or titanium. If cost-effective, such a material could conceivably replace steel in many types of structures.

The center will also provide funding for the following two seed projects, which are of limited duration and smaller scope:

-Research on spintronic materials will be led by Caltech physics professor Nai-Chang Yeh. A promising new research avenue in the physics of composite materials, spintronics seeks to exploit the quantum spin characteristics of electrons to operate electronic devices, rather than the moving of current through wires.

-New materials for the storage and conversions of methanol will be the focus of a group led by Associate Professor of Materials Science and Chemical Engineering Sossina Haile. The goal is to identify materials that are good at the conversion of hydrogen and carbon dioxide to methanol, and conversely, the materials that can best convert methanol to hydrogen for use as a fuel in fuel cells.

According to Atwater, the center will continue to be highly interdisciplinary, not only because researchers from four Caltech divisions will work on the projects, but also because the very nature of the projects draws upon expertise in several branches of science and engineering.

The center will also continue its ongoing efforts in education and public outreach. Current projects include a television series that will be titled Material World, and a materials partnership with Cal State Los Angeles. The latter program has been especially noteworthy in its ongoing efforts to foster materials research and curriculum on the CSULA campus.

The center will continue to build its already extensive network of research collaborations in the private sector with various companies, government laboratories, and other research institutions.

Atwater is the Hughes Professor and professor of applied physics and materials science.

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Robert Tindol
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Alice Gets Ready to Roll

PASADENA, Calif.-The intrepid Alice will soon take center stage at the California Speedway in Fontana. Alice is no diva, but the California Institute of Technology's entrant in this year's Defense Advanced Research Projects Agency Grand Challenge race, a take-no-prisoners field test of autonomously driven robotic vehicles organized by DARPA to speed the development of battlefield-ready robotic tanks, trucks, and other all-terrain vehicles.

Before reaching the race, Alice--a Ford E-350 van modified for off-roading and packed with tons of sophisticated computer servers and sensors--and a field of 42 other entrants will be put through their paces at the National Qualification Event (NQE) which will run from September 28 to October 6 in Fontana. Because of the large number of entrants and the difficulty of the test, the exact time of Alice's qualification run won't be determined until after the start of the NQE.

During the NQE, each vehicle will navigate itself--with no human intervention--through a course of sharp turns, rough roads, power poles, foliage, and other obstacles. The top 20 teams will move on to compete on October 8 in the Grand Challenge finals, a wild ride through the Mojave Desert, over unpaved roads, down trails, and around ditches and sand dunes. The first vehicle to complete the almost 175-mile trek, which will start and end just outside Primm, Nevada, at the California-Nevada state line (the exact course won't be revealed until two hours before start time), in less than 10 hours will receive a $2 million prize.

"I think we'll do great at the NQE," says Richard Murray, professor of control and dynamical systems and leader of Team Caltech. Team Caltech consists of over 50 undergraduates from Caltech, Princeton, Virginia Tech, and Lund University in Sweden, plus high school volunteers, Caltech faculty participants, and engineers from the Jet Propulsion Laboratory, Sportsmobile, Northrop Grumman, and Systems Technology Incorporated. Over the past year, the student team members have combined to put in over 45,000 hours developing Alice.

"The race is going to be tough, although we were farther along with Alice at the beginning of the summer than we were with Bob for the final challenge last year. A lot will depend on how our work over the next two weeks goes," Murray adds, when Alice will continue to be put through her paces in desert test runs and through courses in the parking lots of the Rose Bowl, Santa Anita race track, and the former St. Luke Medical Center. "We are optimizing and tuning our software, trying to get it to respond intelligently to the many types of conditions it might see during the race."

In last year's Grand Challenge, Team Caltech's Bob, a '96 Chevy Tahoe, didn't respond so intelligently to a swath of barbed wire. Bob plowed headlong into it and got hung up, ending his race at mile 1.3. This year, drawing on lessons from Bob's mistakes (Alice's license plate, in fact, reads "I 8 BOB"), the members of Team Caltech have perfected their sensors and software, and their game plan.

"We want Alice to 'see' what is going on around it and drive based on that knowledge," Murray says. "This is much harder than making use of maps and satellite data to locate the roads ahead of time. With five cameras and five laser ranging devices (LADARs), we have a lot more sensors and computers than many of the other teams. This should give us an advantage if the course turns out to be something that is not just running along dirt roads and trails."

Team Caltech has already decided what it will do with the cash prize if Alice wins: $1 million will endow a fund to support CS/EE/ME 75, the class in multidisciplinary project design taken by Team Caltech's students; $500,000 will be divided equally among four student engineering chapters, the American Society of Mechanical Engineers, the Association for Computing Machinery, the Institute for Electrical and Electronics Engineers, and the Society of Women Engineers. The other $500,000 will be divvied up among Team Caltech's student members.

The public is invited to attend the NQE, which will kick off with a 9:00 a.m. opening ceremony on September 28, and the Grand Challenge finals. Admission for both is free, with grandstand seating available. Spectator information is available at the DARPA Grand Challenge website: www.darpa.mil/grandchallenge/spectator_handout.pdf. For the latest information on Team Caltech's NQE start time, visit Team Caltech's website: http://team.caltech.edu.

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Contact: Kathy Svitil (626) 395-8022 ksvitil@caltech.edu

Visit the Caltech Media Relations Web site at: http://pr.caltech.edu/media

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Ronald Scott Dies; Designed Soil Scoopfor Early Unmanned Moon Mission

PASADENA, Calif.--Ronald Scott, a soil engineer who designed the ingenious lunar scoop that first sampled extraterrestrial material, died Tuesday, August 16, at his home in Altadena after a long battle with cancer. He was 76.

Scott was a civil engineering professor at the California Institute of Technology when he worked out a way to test the soil on the moon in anticipation of the Apollo landings. His design was incorporated into the unmanned Surveyor 3 mission, which landed below the rim of a small crater at Oceanus Procellarum on April 20, 1967. The second soft landing on the moon by a U.S. spacecraft (the Surveyor 2 having failed), Surveyor 3 provided crucial details about the strength, texture, and structure of the ground on which astronauts would walk two years later.

According to his longtime colleague Paul Jennings, who is now Caltech's provost, Scott was known in the technical community for numerous other advances in addition to his lunar soil studies. "Ron was an acknowledged intellectual leader in the field of soils mechanics and led the introduction in this country of the use of centrifuges to study problems in the mechanics of soils, particularly during earthquakes.

"He was an exceptional researcher who approached his subject with the motivation of an engineer and the tools of a scientist," Jennings adds. "He was also a noted expert on the cause and mechanics of landslides and other soil failures. He was a consultant on the Baldwin Hills Dam failure in 1963 and the Laguna Hills Bluebird Canyon slide in 1978."

A native of Scotland, Scott had lived in the United States since arriving at MIT in the early 1950s for graduate study. After graduation he spent two additional years at MIT as a researcher, and then worked as a soil engineer with the U.S. Army Corps of Engineers and with Racey, McCallum and Associates in Canada.

He joined the Caltech faculty in 1958 as an assistant professor, and rose through the ranks to become the Dottie and Dick Hayman Professor of Engineering. He retired from active faculty duties in 1998.

During his Caltech career, Scott also worked on various other NASA missions, including the Apollo manned missions, as a member of the soil mechanics team, and the Viking spacecraft that landed on Mars in 1976. He also was a consultant to private industry, local government, and U.S. government agencies on a wide variety of soil engineering problems.

His research interests included the mechanics of deformation and yielding in soils, soil behavior in earthquakes, the physical chemistry and mechanics of ocean-bottom-soil, and freezing and thawing processes in soils. He taught a variety of undergraduate and graduate classes in soil mechanics and foundation engineering at Caltech.

Scott was elected to the National Academy of Engineering in 1974. He was a winner of the American Society of Civil Engineers' Walter L. Huber Civil Engineering Research Prize in 1969, the Norman Medal in 1972, the Thomas A. Middlebrooks Award in 1982, and the American Association for the Advancement of Science's Newcomb Cleveland Prize in 1976.

He is survived by his wife, Pam Scott, and three sons, Grant, Rod, and Craig.

 

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David Rutledge Named Chair of Caltech's Division of Engineering and Applied Science

PASADENA--David Rutledge, a leading researcher in the wireless telecommunication revolution, has been named chair of the Division of Engineering and Applied Science at the California Institute of Technology. The announcement was made today by David Baltimore, president of Caltech.

Rutledge is currently the Kiyo and Eiko Tomiyasu Professor of Electrical Engineering at Caltech, where he has been a faculty member since 1980. He replaces Richard Murray, who has been chair of the E&AS division since 2000. Rutledge will begin his term on September 1, pending approval by the Board of Trustees.

"Dave has a remarkable record of accomplishment in an area of science--electronics--that has a real impact on our daily lives," said Baltimore. "He will provide strong leadership to this important division at a time when invention and discovery in engineering is occurring at a spectacular pace."

Paul Jennings, Caltech's provost, adds that Rutledge "is a distinguished engineer and applied scientist who has won numerous awards for both his research and his teaching.

"The Institute is fortunate that someone of his ability and distinction is willing to assume administrative responsibilities and help guide Caltech. I have known David for many years and look forward to working with him as he takes on his duties as chair."

Jennings also commended Janet Hering, a professor of environmental science and engineering at Caltech who led the search committee, as well as the other committee members.

"David Baltimore and I also take this opportunity to thank Richard Murray for his years of service as chair of the division," Jennings added. "Caltech has benefited greatly from his dedication, vision, and energy during his term of office. We wish him the best of fortune as he concentrates his attention on research and teaching."

Rutledge earned his bachelor's degree at Williams College, his master of arts degree from the University of Cambridge, and his doctorate from UC Berkeley. He joined the Caltech faculty as an assistant professor in 1980, and rose through the faculty ranks to become the holder of the Tomiyasu chair in 2001. He also served as executive officer for electrical engineering from 1999 to 2002.

Rutledge's research group is currently involved in building circuits and antennas for numerous electronic applications. His work on microwave circuits has been important for various advances in wireless communications and has been useful for applications such as radar, remote sensing, and satellite broadcasting.

He is the author of The Electronics of Radio, a book published by Cambridge University Press, and author or coauthor of numerous other publications.

Rutledge is also director of Caltech's Lee Center for Advanced Networking, which aims at creating a global communication system that is as reliable and robust as a basic utility such as water and sewage. The brainchild of Caltech graduate and venture capitalist David Lee, the center focuses on advances in wireless communication that will lead to a new global communication system consisting of a combination of wireless radio frequencies and high-speed fiber-optic cable.

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Research on Biological Jet Flows Could Lead to New Diagnostic Tools for Heart Disease

PASADENA, Calif.--If you're a squid, your typical day consists of leisurely squirting water behind you to move forward, and occasionally squirting larger quantities of water behind you to stay off someone else's lunch menu. If you're a human with heart disease, your day consists of pumping blood through your heart valves much more forcefully than you did when you were young and healthy.

Is there any fundamental connection between these two seemingly dissimilar events? The answer is turning out to be yes, and moreover that a better understanding of what they have in common could lead to a new and improved diagnostic tool for heart disease.

In a new paper in the Proceedings of the Royal Society, California Institute of Technology engineers John Dabiri and Mory Gharib report on their work in understanding the fundamental nature of biological fluid transport. Specifically, they look at the way that vortex formation is optimized and controlled by various organisms, and how jets of fluid can be manipulated to affect energy transport and system efficiency.

"Heart disease typically manifests itself in problems with fluid transport, so if we can learn general principles of effective fluid transport from other animal systems, then we can potentially identify new strategies to diagnose and treat heart failure," says Dabiri, who recently joined the Caltech faculty as an assistant professor of bioengineering and aeronautics. Gharib, who was Dabiri's graduate adviser at Caltech, is the Liepmann Professor of Aeronautics and Bioengineering.

The researchers' strategy is to apply the same principles that have gone into the refinement of airplane and spacecraft designs to matters of biomedical concern. The landing of a space shuttle and the operation of a human heart may seem unrelated, but the fluid flow involved in both cases obeys the same general physical laws. Therefore in both instances one can apply "reverse engineering," in which one looks at a complex system already in existence and tries to understand its fundamentals.

In the case of biological fluid flow, scientists know that a number of animals regularly manipulate jet flows for their survival. Therefore, trying to understand precisely how these jet flows function can lead to a new way of understanding how to fix the individual parts that are broken.

"If you can figure out the basic design principles that allow the left ventricle to function well in terms of fluid transport, then creating therapies for disease may not be much different from redesigning an airplane wing for improved performance using the appropriate aerodynamic principles," Dabiri says.

Since many kinds of heart disease are known to be reflected in blood flow near the heart valves, Dabiri, Gharib, and Dr. Arash Kheradvar, an MD who is working for his Ph.D. in Gharib's group, hope to be able to determine the overall health of the heart by viewing this smaller subsection. The diagnostic procedure might turn out to be as simple as taking an echocardiogram of a patient's heart-in much the same way that a sonogram is currently taken of a pregnant woman's abdomen to monitor the health of a fetus.

Then, if a problem with the jet flow through the valve were to be identified, the discovered design principles could be used to direct surgeons on how to correct the malfunction.

Further laboratory and clinical research is needed before the current results will translate into such a practical diagnostic tool, Dabiri says. However, this study takes an important step toward this goal by developing the paradigm under which future research will proceed.

 

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New Propane-Burning Fuel Cell Could Energize a Future Generation of Small Electrical Devices

PASADENA, Calif.--Engineers have created a propane-burning fuel cell that's almost as small as a watch battery, yet many times higher in power density. Led by Sossina Haile of the California Institute of Technology, the team reports in the June 9 issue of the journal Nature that two of the cells have sufficient power to drive an MP3 player. If commercialized, such a fuel cell would have the advantage of driving the MP3 player for far longer than the best lithium batteries available.

According to Haile, who is an associate professor of materials science and of chemical engineering at Caltech, the new technology was made possible by a couple of key breakthroughs in fuel-cell technology. Chief among these was a novel method of getting the fuel cell to generate enough internal heat to keep itself hot, a requirement for producing power.

"Fuel cells have been done on larger scales with hydrocarbon fuels, but small fuel cells are challenging because it's hard to keep them at the high temperatures required to get the hydrocarbon fuels to react," Haile says. "In a small device, the surface-to-volume ratio is large, and because heat is lost through the surface that is generated in the volume, you have to use a lot of insulation to keep the cell hot. Adding insulation takes away the size advantage."

The new technology tackles this problem by burning just a bit of the fuel to generate heat to maintain the fuel cell temperature. The device could probably use a variety of hydrocarbon fuels, but propane is just about perfect because it is easily compressible into a liquid and because it instantly becomes a vapor when it is released. That's exactly what makes it ideal for your backyard barbecue grill.

"Actually, there are three advances that make the technology possible," Haile says. "The first is to make the fuel cells operate with high power outputs at lower temperatures than conventional hydrocarbon-burning fuel cells. The second is to use a single-chamber fuel cell that has only one inlet for premixed oxygen and fuel and a single outlet for exhaust, which makes for a very simple and compact fuel cell system. These advances were achieved here at Caltech."

"The third involves catalysts developed at Northwestern University that cause sufficient heat release to sustain the temperature of the fuel cell." In addition, a linear counter-flow heat exchanger makes sure that the hot gases exiting from the fuel cell transfer their heat to the incoming cold inlet gases.

Although the technology is still experimental, Haile says that future collaborations with design experts should tremendously improve the fuel efficiency. In particular, she and her colleagues are working with David Goodwin, a professor of mechanical engineering and applied physics at Caltech, on design improvements. One such improvement will be to incorporate compact "Swiss roll" heat exchangers, produced by collaborator Paul Ronney at USC.

As for applications, Haile says that the sky is literally the limit. Potential applications could include the tiny flying robots in which the defense funding agency DARPA has shown so much interest in recent years. For everyday uses, the fuel cells could also provide longer-lasting sources of power for laptop computers, television cameras, and pretty much any other device in which batteries are too heavy or too short-lived.

In addition to Haile, the other authors are Zongping Shao, a postdoctoral scholar in Haile's lab; Jeongmin Ahn and Paul D. Ronney, both of USC; and Zhongliang Zhan and Scott A. Barnett, both of Northwestern.

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Autonomous Racing: Bob, Meet Alice

PASADENA, Calif. - We Went! We Raced! We Ate Barbed Wire! So stated the unabashedly honest headline on the "Team Caltech" website last year. It was lamenting how the California Institute of Technology's autonomous truck, nicknamed Bob, fared in last March's DARPA Grand Challenge desert road race.

The 142-mile race from L.A. to Las Vegas called for a vehicle that could operate with complete autonomy (no driver or remote control) and finish a course that included dirt trails and open desert in 10 hours or less. Bob completed about 1.3 miles of the course; its demise was getting tangled in barbed wire. The farthest any entry made it was 7.4 miles.

Enter Alice. It's the new driverless vehicle being built by Team Caltech 2005--a group of undergrads (more than 50 in the last nine months), graduate students, and faculty advisers--that will compete in this year's race on October 8. "We are light years ahead with Alice with respect to where we were last year at the same point with Bob," says project manager Richard Murray, a professor of control and dynamical systems. That may explain why Alice sports the license plate, "I 8 Bob."

The DARPA Grand Challenge race (DARPA stands for the Defense Advanced Research Projects Agency) is intended to hasten the research and development of autonomous ground vehicles that could ultimately be used to ferry supplies to the front lines or transport wounded soldiers. "The technology is also likely to have ramifications for future automobile technology, especially for helping disabled drivers," says Joel Burdick, a technical adviser and a professor of mechanical engineering and bioengineering. "And it will likely have an impact on future autonomous space exploration as well."

The race is open to individuals and organizations, and has a $2 million first prize. This year's desert racecourse will be similar to last year's, but participants won't know the exact route until two hours before the race.

Bob, the 1996 Chevrolet Tahoe four-wheel-drive SUV used last year, has been replaced by a Ford E-350 van that has been customized for off-road travel by a company called Sportsmobile, based in Fresno, that specializes in building 4X4 vehicles. It is powered by a six-liter diesel engine that allows for long periods of idling at low fuel consumption. Special hardware has been mounted on the bumper and roof to hold the various sensors that serve as the vehicle's eyes during autonomous driving. Inside, the students have transformed Alice into a complete software lab that includes its brain--seven Dell servers sitting in temperature controlled and shock-resistant housing--and four seats with racing harnesses that, during testing, keep the students safe while strapping them down enough to let them type on a computer keyboard during rough off-roading.

Although they won't know officially until June, presumably Alice passed an important test on May 11, when DARPA officials made a site visit to see how the truck was progressing. (The visits are intended to whittle down the 100-plus entries to a final 40 teams that will actually race.) "This was due, no doubt, to what was approximately 100 hours of additional work the students put into Alice in the week prior," says Burdick, who notes the students can receive academic credit for two classes by working on Alice.

The visit took place in the parking lot at Santa Anita racetrack. Alice completed two runs of the course in approximately 45 seconds, avoiding all obstacles, but crunched a trashcan in its third run and made an unnecessary safety stop when it "thought" it spied an obstacle. On run four, it re-ran the first part of the course (including the obstacles from the third run) at 15 mph, then demonstrated higher driving speeds while navigating through a cluttered field of trashcans.

"We've learned some valuable lessons and have some advantages this year," says Murray. "For one thing, last year's race took place during finals week; this year they'll be over. We've learned some tricks--for example, Alice is completely street legal, so we don't have to haul it on a trailer everywhere we go, like we did with Bob. And we now have the advantage of knowing what the actual racecourse will be like, so we'll be doing a lot of testing in the desert over the summer."

While no one is going out on a limb to say Caltech will win the race ("There's a lot of good competition," says Murray), Burdick, for one, predicts that someone will complete this year's course. That is, he says, "a remarkable evolution of the technology and a testament to the hard work of all the teams."

To win the race in less than 10 hours, as the rules state, Alice will need to average a speed of 20 mph. "But we believe we will have to be able to drive at speeds of up to 50 mph for portions of the course in order to maintain that average, since some sections will be slow going," notes Murray. This, in a driverless, fully autonomous vehicle.

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Five from Caltech Faculty Elected to American Academy of Arts and Sciences

PASADENA, Calif.-Five faculty members at the California Institute of Technology are among this year's newly elected fellows of the American Academy of Arts and Sciences. They join 191 other Americans and 17 foreign honorees as the 225th class of fellows of the prestigious institution that was cofounded in 1780 by John Adams.

This year's new Caltech inductees are Barry Barish, the Linde Professor of Physics and director of the Laser Interferometer Gravitational-Wave Observatory (LIGO); Andrew Lange, the Goldberger Professor of Physics; Barry Simon, the IBM Professor of Mathematics and Theoretical Physics; David Tirrell, chair of the Division of Chemistry and Chemical Engineering and McCollum-Corcoran Professor and professor of chemistry and chemical engineering; and William Bridges, the Braun Professor of Engineering, Emeritus.

The five from Caltech join an illustrious list of fellows, both past and present. Other inductees in the 225th class include Supreme Court Chief Justice William Rehnquist, Angels in America author Tony Kushner, Academy Award-winning actor Sidney Poitier, former NBC Nightly News anchor Tom Brokaw, Washington Post CEO Donald Graham, and Pulitzer Prize-winning cartoonist Art Spiegelman. Past fellows have included George Washington, Benjamin Franklin, Ralph Waldo Emerson, Albert Einstein, and Winston Churchill.

According to the academy's president, Patricia Meyer Spacks, the fellows were chosen "through a highly competitive process that recognizes individuals who have made preeminent contributions to their disciplines and to society at large."

"Throughout its history, the Academy has convened the leading thinkers of the day, from diverse perspectives, to participate in projects and studies that advance the public good," said Executive Officer Leslie Berlowitz.

The academy is an independent policy research center that focuses on complex and emerging problems such as scientific issues, global security, social policy, the humanities and culture, and education.

The new fellows and foreign honorary members will be formally recognized at the annual induction ceremony on October 8 at the academy's headquarters in Cambridge, Massachusetts.

 

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Seismic experiments provide new clues to earthquake wave directionality and growth speed

PASADENA, Calif.--In recent years, seismologists thought they were getting a handle on how an earthquake tends to rupture in a preferred direction along big strike-slip faults like the San Andreas. This is important because the direction of rupture has a profound influence on the distribution of ground shaking. But a new study could undermine their confidence a bit.

Reporting in the April 29 issue of the journal Science, researchers from the California Institute of Technology and Harvard University discuss new controlled laboratory experiments using dissimilar polymer plates to mimic Earth's crusts. The results show that the direction of rupture that controls the pattern of destruction is less predictable than recently thought.

The results explain puzzling results from last year's Parkfield earthquake, in which a northwestward rupture occurred. A southeastward rupture had been predicted on the basis of the two past earthquakes in the area and on numerical simulations. Also, during the recent large earthquakes in Turkey, some ruptures have occurred in the direction opposite to what happened in the past and are thought to involve unusually high speeds along that direction.

The phenomenon has to do with the basic ways rupture fronts (generating seismic waves) are propagated along a boundary between two materials with different wave speeds--an area of research that is yielding interesting and important results in the engineering laboratory.

The reason this is important is that geophysicists, knowing the wave speeds of the materials in different tectonic plates and the stresses acting on them, could someday have an improved ability to predict which areas along a major fault might be more powerfully hit. In effect, a better fundamental knowledge of the workings of Earth's plates could lead to a better ability to prepare for major earthquakes.

In the experiment, Caltech's von Kármán Professor of Aeronautics and Mechanical Engineering Ares Rosakis (the director of the Graduate Aeronautical Laboratories); his cross-campus colleague, Smits Professor of Geophysics Hiroo Kanamori; Professor James Rice of Harvard University; and Caltech grad student Kaiwen Xia, prepared polymer plates to mimic the effects of major strike-slip faults. These are faults in which two plates are rammed against each other by forces coming in at an angle, and which then spontaneously snap (or slide) to move sideways.

Because such a breaking of lab materials is similar on a smaller scale to the slipping of tectonic plates, the measurement of the waves in the polymer materials provides a good indication of what happens in earthquakes.

The team fixed the plates so that force was applied to them at an acute angle relative to the "fault" between them. The researchers then set off a small plasma explosion with a wire running to the center of the two polymer plates (the "hypocenter"), which caused the two plates to quickly slide apart, just as two tectonic plates would slide apart during an earthquake.

The clear polymer plates were made of two different materials especially selected so that their stress fringes could be photographed. In other words, the waves and rupture fronts that propagate through the system due to this "laboratory earthquake event" showed up as clearly visible waves on the photographic plates.

What's more, if the rupture fronts are super-shear, i.e., faster than the shear speed in the plates, they produce a shock-wave pattern that looks something like the Mach cone of a jet fighter breaking the sound barrier.

"Previously, it was generally thought that, if there is a velocity contrast, the rupture preferentially goes toward the direction of the slip in the low-velocity medium," explains Kanamori. In other words, if the lower-velocity medium is the plate shifting to the west, then the preferred direction of rupture would typically be to the west.

"What we see, when the force is small and the angle is small, is that we simultaneously generate ruptures to the west and to the east, and that the rupture fronts in both sides go with sub-shear speed," Rosakis explains. "But as the pressure increases substantially, the westward direction stays the same, but the other, eastward direction, becomes super-shear. This super-shear rupture speed is very close to the p-wave speed of the slower of the two materials."

To complicate matters even further, the results show that, when the experiment is done at forces below those required for super-shear, the directionality of the rupture is unpredictable. Both waves are at sub-shear speed, but waves in either direction can be devastating.

This, in effect, explains why the Parkfield earthquake last year ruptured in the direction opposite to that of past events. The experiment also strongly suggests that, if the earthquake had been sufficiently large, the super-shear waves would have traveled northwest, even though the preferred direction was southeast.

But the question remains whether super-shear is necessarily a bad thing, Kanamori says. "It's scientifically an interesting result, but I can't say what the exact implications are. It's at least important to be aware of these things.

"But it could also mean that earthquake ruptures are less predictable than ever," he adds.

Contact: Robert Tindol (626) 395-3631

Writer: 
RT

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