June/July 2005
Professor Alexandre Bayen joined the Department of Civil and Environmental Engineering faculty in January 2005. |
Air traffic controllers have a tough job. Busy airspaces can be logistical nightmares, requiring fast planning to help planes depart and arrive on schedule without crashing into each other. Still, accidents do occasionally occur, like in 2002 when a Russian passenger jet and an American cargo plane collided over southern Germany killing 71 people. UC Berkeley civil engineer Alexandre Bayen is applying mathematics to the problem of congested airspaces. His work could improve the safety of the skyways while enabling airports to run like clockwork.
"The long term vision is a bit like what you might see in Star Wars films when streams of aircraft in the sky are crisscrossing each other beautifully," Bayen says.
The aim is to develop a system that would provide aircraft with the computational smarts to automatically avoid each other. Initially, the system would recognize when an aircraft is acting unsafely and suggest an evasive maneuver. Eventually, Bayen says, a system could potentially take over control from the pilot in an emergency situation.
The first step though is to develop the mathematical algorithms that would be at the heart of an advanced collision avoidance system. To do that, Bayen and his colleagues use formulas to describe the set of all possible positions of the two aircraft relative to each other. By solving the problem for the worst-case scenario, they prepare for the worst and hoping for better.
"We solve it under the assumption that one aircraft will do everything possible to avoid being hit and that the intruder aircraft is trying its hardest to collide," Bayen says. "In real life, hopefully the intruder won't act so badly."
To deal with the complexities of the problem, Bayen employs the mathematics of level sets, a method developed in 1988 at UC Berkeley and UCLA to track and simulate shifting boundaries of dynamic objects and materials. Rather than compute each of the aircraft's possible trajectories, the planes are represented by level sets incorporating an infinite number of trajectories.
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"If you can compute these sets, it gives you a mathematical border," Bayen says. "Outside the border, you're safe. Inside, you're not safe. As soon as an aircraft hits the border of the unsafe set, the pilot will receive an alert that might say, 'Warning! Here is the way to avoid a collision.' We can prove mathematically that if the pilot responds right away, he or she can escape the danger."
In Bayen's laboratory, the researchers are applying the algorithms to air traffic computer simulations developed jointly with NASA Ames. Meanwhile, his former adviser at Stanford University , aeronautics professor and Berkeley alumna Claire Tomlin, is experimenting with hardware implementations based on the algorithms and testing the systems on manned and unmanned aerial vehicles.
Someday, other algorithms that Bayen is developing could aid air traffic controllers at busy airports. Due to safety constraints, the air traffic controllers assign various maneuvers--holding patterns and turns, for example--that ensure a buffer of time between aircraft landings. However, this buffer decreases the efficiency of the airspace.
"It's a very high workload for the humans in charge of that airspace," Bayen says. "So the question is: Can we automatically assign maneuvers so that the aircraft are delivered at an optimal rate? The key is to translate what a human air traffic controller does into a mathematical language."
A preliminary implementation of their optimization algorithms applied to historical air traffic data was promising, Bayen says. Now they're developing techniques they hope could compute optimal maneuver assignments in real-time to crank up an airspace's efficiency, reducing delays and increasing arrival predictability. These suggestions could then appear as advisories on air traffic controllers' display screens.
"Everybody agrees automation should become more important in air traffic control, but there's no global consensus of what should and should not be automated," Bayen says. "Decisions about deploying new automation technologies involve many different scientific, social, and political factors. Our main goal is to overcome the scientific challenges which prevent these decisions from being made."
Pro New Nuke
by David Pescovitz
The first female nuclear engineering department chair of a Top 10 school in the nation, Jasmina Vujic is also the vice president of the Tesla Memorial Society of New York. |
In April, Greenpeace co-founder Patrick Moore, standing before members of the U.S. Congress, stated that "nuclear energy is the only non-greenhouse-gas-emitting power source that can effectively replace fossil fuels and satisfy global demand." In last month's issue of Technology Review, 1960s icon Stewart Brand, creator of the Whole Earth Catalog, wrote that "the only technology ready to fill the gap and stop the carbon dioxide loading of the atmosphere is nuclear power." Many environmentalists are none-too-thrilled at these public comments from their allies, current or former. On the other hand, UC Berkeley professor Jasmina Vujic is thrilled. According to her research, Moore and Brand are absolutely right.
"This country has neglected nuclear energy for the last 20 or 30 years, but nuclear energy will be the way of the future if the United States wants to have energy independence and reduce the human influence on global climate," says Vujic, who as the recently appointed chair of Berkeley's Department of Nuclear Engineering is the first female to hold such a position in the nation.
According to the Intergovernmental Panel on Climate Change (IPCC), the observed climate warming over the last 50 years is due to an increase in concentrations of greenhouse gasses like carbon dioxide in the atmosphere. Nearly all of that carbon dioxide is generated by fossil fuels like coal and oil burned for energy. A coal-fired power plant capable of producing 1000 megawatts of electricity burns 7,300,000 kilograms of coal per day and releases upwards of 1,000 grams of carbon dioxide into the atmosphere per kilowatt hour. The equivalent nuclear fission plant consumes just 3.2 kilograms of uranium. Meanwhile, it emits almost no carbon dioxide. While other renewables like solar energy and wind are clean, many argue that the technology isn't efficient or practical enough yet to compete with coal.
Nuclear fission is obviously not waste-free though. And that's one of the main reasons that in this country, nuclear energy has been on the back burner since the 1970s. Currently, 20 percent of the electricity in the United States is generated by approximately 100 nuclear fission power plants, most of which went online in the 1970s. The radioactive waste from those plants is stored in spent fuel pools or casks near the plants.
A schematic illustration of the ENHS "nuclear battery" reactor. (Click for larger image.) |
Centralized storage facilities certainly make more sense, Vujic explains, in terms of environmental impact and also to prevent the radioactive material from being stolen by groups who might use it to make "dirty bombs." Even as the Yucca Mountain nuclear repository site is embroiled in controversy, UC Berkeley researchers are developing ways to deal with the waste issue, from assessing proposed repository performance to developing new reactor designs that could produce ten to twenty times less waste.
"You need to ensure that nothing bad would happen for 10,000 years," Vujic says. "We've solved many of those engineering challenges. Our problem with radioactive waste is more political than technical now."
Much of the waste could be recycled, Vujic explains. The U.S. 's current breed of nuclear plants are based on a once-through "open cycle" with fuel. Newer plants employ a "closed cycle," Vujic says. For example, plants in France , (where 77 percent of the electricity comes from nuclear power), China , Russia , and the United Kingdom employ this approach.
"They take out the rest of the uranium and plutonium and then deal with the real waste," she says. "We're looking at ways to transform that spent fuel into something shorter lived before you place it in the repository."
At UC Berkeley, researchers are exploring techniques to optimize the fuel cycle and also improve waste management. Indeed, the Encapsulated Nuclear Heat-Source (ENHS) reactor design, a "nuclear battery" developed by professor Ehud Greenspan in collaboration with Vujic and others, promises an overall increase in fuel utilization nearly 50 times that of the once-through cycle.
The Berkeley research focuses on the development of so-called Generation IV nuclear energy systems. Members of the U.S. Department of Energy-led Generation IV International Forum (GIF) identified six nuclear systems that they believe could offer advantages in sustainability, safety, economic competitiveness, and proliferation resistance.
Vujic is not only confident that nuclear energy could help solve our electricity woes, but she also believes that the Generation IV reactors would drive a shift from oil to hydrogen.
"Besides electricity, one of the outputs of a nuclear power plant is heat," she says. "And with some of the new designs, those high temperatures could be used for efficient production of hydrogen."
Even with seemingly so many pluses, and support from the current presidential administration, a nuclear revival could be a tough sell to the public. Vujic, however, is optimistic that many people are slowly beginning to see the brighter side of nuclear energy. She cites a 2001 statewide Field Poll in California showing that 59 percent of those surveyed support the construction of new nuclear power plants in the state. The pro-nuke number in 1984, the last time the Field Poll posed the question, was only 33 percent.
"The moment you try to turn on your light and there is no power, you have a different perspective," Vujic says.
Students Sell New Cell Phone Technology
by David Pescovitz
Harmonic Devices, winners of the UC Berkeley Business Plan Competition. From left to right: Justin Black, John Hwang, Gianluca Piazza, Phil Stephanou, and Kenny Miller. |
For two years, UC Berkeley Engineering graduate students Gianluca Piazza, Phil Stephanou, and Justin Black were developing an atomic clock far tinier and cheaper than today's technology. They hoped that in the future, their sugarcube-sized device, accurate down to ten quandrillionths of a second per day, might improve data encryption, speed up computer networking, and boost the accuracy of the Global Positioning System (GPS). Then opportunity rang. The students realized that one of their clock components also had the potential to revolutionize cellular telephone electronics. In the last few months, their idea has brought them gold in three major business plan competitions. Now it's time to start a company.
"There are probably a few hundred thousand atomic clocks that our technology could replace," says Piazza, who hopes to earn his PhD in electrical engineering later this year. "Compare that to 700 million cell phones sold last year. The potential impact is much greater."
A scanning electron micrograph (SEM) showing a circular ring resonator with an inner radius of just 90 microns, less than the diameter of a human hair. (courtesy the researchers) |
Already, mobile phones are bursting with features, from cameras to video playback capabilities. At the same time, various cellular networks around the globe operate on different frequencies, or bands, yet we want our phones to work wherever we are, preferably with Internet connectivity . The problem is that as new features emerge, and our demand grows for tri-band and even quad-band phones, the number of components that must be packed into each handset also increases. The students' invention enables manufacturers to add more functionality to phones while keeping the price down and the form factor svelt.
Wireless radios depend on crystal oscillator clocks to provide an accurate timing pulse and frequency reference. Meanwhile, two types of filters ensure that only the intended bit of the scarce frequency spectrum is used for each call. Unfortunately, these types of components are usually bulky, power-hungry, and expensive. While integrated circuits are fabricated on silicon, the quartz crystal and filter are built on more exotic materials. This means they can't be manufactured as part of the main integrated circuit that handles a phone's wireless tasks.
"Right now, you have to package these things separately and solder them on to the circuit board," says Stephanou, a mechanical engineering PhD candidate. "Our technology is compatible with the same fabrication techniques used to make the RF circuits, so you can just build them on the silicon right next to the phone electronics."
An array of circular- and square-shaped MEMS resonators function as filters for a wireless transceiver. (courtesy the researchers) |
The main ingredient in the new device is a tiny resonator, the heart of the atomic clock that the students developed with professor Albert Pisano, chair of the Department of Mechanical Engineering and a director of the Berkeley Sensor and Actuator Center (BSAC). Pisano is Piazza and Stephanou's faculty adviser while Black conducts his resonator research with BSAC co-director, electrical engineering and computer sciences professor Richard White. The MEMS (micro-electromechanical Systems) resonator is like a microscopic guitar string that vibrates only at a specific frequency when it's plucked. That frequency can be used as a reference by both the clock and the filters.
Unlike other MEMS resonators that are long and narrow, the students' device is shaped like a donut with a radius thinner than a human hair. It's fashioned from aluminum nitride, a material that resonates in the presence of an electric field. The resonant frequency is determined by the width of the ring.
"Rather than a linear resonator, the ring structure provides a larger area so the structure can vibrate radially and that improves the performance," Stephanou says.
Another benefit is that several resonators of various sizes can be fabricated onto a single integrated circuit. That way, a phone can operate on multiple bands without the additional cost or space requirements of multiple off-chip filters.
Late last year, the three engineers teamed up with Berkeley MBA students Kenny Miller and John Hwang to explore the business potential of their idea. Patents were filed and a company, Harmonic Devices, was born. This spring, their collaborative business plan won first place in the Berkeley Nanotechnology Club's Nano Opportunity Challenge, the University of San Francisco 's International Business Plan Competition, and the UC Berkeley Business Plan Competition. As the students work to complete their PhDs, Harmonic Devices is actively seeking venture capital to take their device to market.
"Business is a protocol that allows you to take what you've learned in the lab and apply it in society," Stephanou says. "Otherwise, these kinds of things would remain research projects and academic papers. The only way we're going to get this into people's cell phones is to make a business case for it."
In April, Sehat Sutardja and Weili Dai spoke to Berkeley students about engineering and entrepreneurship. [View webcast] |
In the sixth grade, Sehat Sutardja (M.S.'83, Ph.D.'88 EECS) told his parents he wanted a career in electronics. This was the 1970s, and that meant repairing TVs and radios. His parents wanted him to be a medical doctor, not a TV repairman. But Sutardja loved electronics. At night, he dreamed about the wonderful things electronics could do. Thirty years later, Sutardja still loves the field. Together with two other Berkeley alumni, he's parlayed his passion and dreams into a wildly successful technology company, Marvell (pronounced mar-VELL) Technology Group, for which he serves as CEO.
It has taken Sunnyvale-based Marvell only ten years to grow from a three-person, family-funded startup to a 1,800-employee, billion-dollar technology company. Some would consider that extraordinary, given Silicon Valley 's tough times and the maturity of the semiconductor industry.
As Berkeley students, Sutardja and his brother Pantas (B.S.'83, M.S.'85, Ph.D.'88 EECS) studied hard. Sehat worked under former EECS professor and now executive vice chancellor and provost Paul Gray, an expert in analog integrated circuit design. "By being close to the top professors, it pushed all of us to work harder," says Sehat. "We had to come up with results that were better than the other guys."
After graduation, the two brothers and Sehat's wife Weili Dai (B.A.'84 CS) went to work in the industry. Sutardja concentrated on analog signal processing; seven years later both he and his brother were focusing on digital, although at separate companies. After a few years, they realized it wasn't just a black-and-white choice between analog or digital. "You need both to solve future problems of communications," says Sutardja. The two decided to combine analog and digital into a single company, drawing on the combination of their expertise.
In 1995, the three partners formed Marvell. The early years were hard, says Sutardja. They worked all the time, nights and weekends, struggling to perfect their product. They didn't pay themselves salaries and lived on the cheap. They hardly saw their families. Even when their first product came out, they struggled to convince customers to buy it.
"We were too small, way too risky," recalls Sutardja. "That really got to us. It was just luck getting our customers, but we were able to build the products that our competitors couldn't. After three or four years, we got one customer. The next year, another."
The three entrepreneurs made it. Two summers ago, Dai and the Sutardjas were recognized for their collective passion for innovation, technology leadership, and business success with Ernst & Young's coveted Entrepreneur of the Year Award.
With all his success and experience, Sutardja has some advice for students. "Learn as much as possible, in software, biology, advanced physics, all the fields. It's not sufficient to know a single field of knowledge. A lot of people stop learning when they want to become a businessperson. That's the biggest mistake they can make."
