It was a search for the essence of things that lead to the memristor, says UC Berkeley professor Leon Chua.
This week, HP Labs announced it had made a memristor, or memory resistor, a fundamental circuit element first theorized by Chua decades ago. If they become commercially practical to make, memristors could lead to very dense, energy-efficient memory chips that don't cost much because they don't need much silicon. A memristor has a variable resistance; as a result, memristors can "remember" how much charge was applied to it. (See here for more on HP's memristor.)
While most have accepted Chua's work, it has mostly been considered theoretical. But how did Chua come up with the mathematical formula for proving memristors exist in the first place?
17 memristors in a row, freshly made by HP
(Credit: J.J. Yang, HP Labs)He started looking at what truly defined different circuit elements, similar to the approach Aristotle took when trying to define substance and essence.
"I asked, 'What is a resistor? What is a capacitor?' No one was really asking that," Chua said. If you asked someone what a resistor was, they'd say, 'It gets hot so let's make an oven out of it.' That was the mentality."
Chua then took four variables: voltage, current, charge, and flux. A resistor was defined by current plus voltage, he said. A capacitor was defined by voltage plus charge. Flux and current made an inductor. That took care of three out of four of the known circuit elements.
There was only one possible combination left, according to Chua. Flux plus charge, which he defined as a memristor.
Why did it take so long to eventually make a memristor? He gave two reasons. One, researchers chalked up evidence pointing to memristors, or effects created by memristors, as anomalies in their own experiments.
Second, material science has made huge strides. The memristors developed by HP measure 5 nanometers across. "That's the length of five sugar molecules," Chua said. "The memory effect dominates."
Leon Chua
(Credit: UC Berkeley)Chua noted that he actually made a rough prototype back when the paper first came out, but it was impractical and manufacturers weren't interested in developing it.
And, it's not the first time it's taken a while to prove something. He pointed to Aristotle's law of motion. Not familiar with it? That's because it turned out to be wrong. Aristotle said that force should be proportional to velocity. Centuries later, Newton showed that force was actually proportional to acceleration.
"They were looking at the wrong variable," he said. "The same thing happened here."
UNION CITY, Calif.--On a cool, overcast morning in the parking lot of a Lowe's hardware store, 100 UC Berkeley students lined up in rows ready to jump into a bevy of idling vehicles.
With media and VIPs from companies like Nokia, Navteq, General Motors, BMW, and CalTrans looking on, wave after wave of students left the parking lot to drive a 10-mile stretch of the nearby 880 freeway as part of a large-scale experiment to test how cell phones can monitor and predict traffic.
The test, conducted all day Friday, was put on by the California Center for Innovative Transportation (CCIT) as a joint project between Nokia, CalTrans, and Berkeley's Department of Civil and Environmental Engineering.
Each student car was issued a Nokia N95 phone with GPS and special traffic-monitoring software developed by Nokia's Palo Alto, Calif.-based research lab--plus a Bluetooth headset. As the students drove the freeway, the phone sent data about each car's speed and position back to the company's research facility. The data is compiled and used to predict traffic patterns and help drivers get where they need to be quickly. Nokia hopes that one day the system could be a significantly cheaper way to track traffic than the permanent sensors installed in roadways or next to them because it uses equipment most people already own: cell phones.
Alex Bayen, a professor of civil and environmental engineering and lead researcher on the project for Berkeley, called the experiment "a glimpse into the future of traffic information collecting and data processing."
An obvious concern is privacy, and one that Bayen was quick to address. The information sent from each phone is designed to keep each "moving traffic sensor" anonymous. When the information is sent to Nokia, Bayen says all of the personal identifying information is stripped from the data, and encryption methods on the level of what banks use is employed to keep information private. Also, the traffic monitoring software only broadcasts information when it senses the phone has entered a specific area, like a highway. It does not track the phones that are on cul-de-sacs, for example.
The data from the phones will be sent back to the Nokia Research Center where a team will analyze the usability of the data and determine what comes next.
Nokia Chief Technology Officer Bob Iannucci, who was on hand for the field test, said this particular project is moving at a more aggressive pace than most of Nokia's research because of the potential impact of the experiment. The phone maker hopes to expand the experiment from 100 to possibly 1,000 people soon. And instead of participating in a one-day test, users would be invited to use the traffic monitoring software in the course of their daily routines.
To see CNET News.com's video of the experiment, click here.
University of California at Berkeley's nanoradio might be a 100 billion times smaller than the first commercial radios, but it plays the hits that never die.
Alex Zettl, a professor of physics at the university, has made a radio out of a single carbon nanotube that's about 10,000 times thinner than a human hair. It runs on batteries and you need headphones to use it, but it tunes in stations on the FM dial.
Zettl and his team last year received their first FM broadcast, which turned out to be "Layla" from Derek and the Dominoes. They also caught "Good Vibrations." In homage to the 100th anniversary of the first voice and music transmission, they transmitted (and tuned in to) a recording of "Largo," from the Handel opera Xerxes. It was the first successful radio transmission of music in 1906.
The nanotube serves as the antenna, tuner, amplifier, and demodulator in the radio. In an ordinary radio, these are all separate components. The nanotube vibrates thousands to millions of times per second in tune with the radio wave.
Carbon nanotubes are the miracle material of the chemistry world. Stronger than steel yet very light, nanotubes can also transmit electricity faster than metals as well as emit light. Scientists speculate that nanotubes one day could be incorporated into silicon chips, power lines, medicines, bridges, and aircraft parts. Nanotubes are essentially cylinders made completely from carbon atoms; the incredibly strong bonds that can be formed between carbon atoms are what give nanotubes their unusual properties.
Right now, though, nanotubes are mostly used to make things like tennis rackets and car panels stronger without adding weight.
"The nanotube radio may lead to radical new applications, such as radio-controlled devices small enough to exist in a human's bloodstream," wrote Zettl and his team in a paper that was released online Wednesday and will be published November 6 in Nano Letters.
The nanoradio could also be used to measure the mass of atoms.
YouTube is now an important teaching tool at UC Berkeley.
The school announced on Wednesday that it has begun posting entire course lectures on the Web's No.1 video-sharing site.
Berkeley officials claimed in a statement that the university is the first to make full course lectures available on YouTube. The school said that over 300 hours of videotaped courses will be available at youtube.com/ucberkeley.
Berkeley said it will continue to expand the offering. The topics of study found on YouTube included chemistry, physics, biology and even a lecture on search-engine technology given in 2005 by Google cofounder Sergey Brin.
"UC Berkeley on YouTube will provide a public window into university life, academics, events and athletics, which will build on our rich tradition of open educational content for the larger community," said Christina Maslach, UC Berkeley's vice provost for undergraduate education in a statement.
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