New silicon memory chip developed
May 18, 2012
The first purely silicon oxide-based ‘Resistive RAM’ memory chip that can operate in ambient conditions – opening up the possibility of new super-fast memory – has been developed by researchers at UCL.
Resistive RAM (or ‘ReRAM’) memory chips are based on materials, most often oxides of metals, whose electrical resistance changes when a voltage is applied – and they “remember” this change even when the power is turned off.
ReRAM chips promise significantly greater memory storage than current technology, such as the Flash memory used on USB sticks, and require much less energy and space.
The UCL team have developed a novel structure composed of silicon oxide, described in a recent paper in the Journal of Applied Physics, which performs the switch in resistance much more efficiently than has been previously achieved. In their material, the arrangement of the silicon atoms changes to form filaments of silicon within the solid silicon oxide, which are less resistive. The presence or absence of these filaments represents a ‘switch’ from one state to another.
Unlike other silicon oxide chips currently in development, the UCL chip does not require a vacuum to work, and is therefore potentially cheaper and more durable. The design also raises the possibility of transparent memory chips for use in touch screens and mobile devices.
The team have been backed by UCLB, UCL’s technology transfer company, and have recently filed a patent on their device. Discussions are ongoing with a number of leading semiconductor companies.
Dr Tony Kenyon, UCL Electronic and Electrical Engineering, said: “Our ReRAM memory chips need just a thousandth of the energy and are around a hundred times faster than standard Flash memory chips. The fact that the device can operate in ambient conditions and has a continuously variable resistance opens up a huge range of potential applications.
“We are also working on making a quartz device with a view to developing transparent electronics.”
For added flexibility, the UCL devices can also be designed to have a continuously variable resistance that depends on the last voltage that was applied. This is an important property that allows the device to mimic how neurons in the brain function. Devices that operate in this way are sometimes known as ‘memristors’.
This technology is currently of enormous interest, with the first practical memristor, based on titanium dioxide, demonstrated in just 2008. The development of a silicon oxide memristor is a huge step forward because of the potential for its incorporation into silicon chips.
The team’s new ReRAM technology was discovered by accident whilst engineers at UCL were working on using the silicon oxide material to produce silicon-based LEDs. During the course of the project, researchers noticed that their devices appeared to be unstable.
UCL PhD student, Adnan Mehonic, was asked to look specifically at the material’s electrical properties. He discovered that the material wasn’t unstable at all, but flipped between various conducting and non-conducting states very predictably.
Adnan Mehonic, also from the UCL Department of Electronic and Electrical Engineering, said: “My work revealed that a material we had been looking at for some time could in fact be made into a memristor.
“The potential for this material is huge. During proof of concept development we have shown we can programme the chips using the cycle between two or more states of conductivity. We’re very excited that our devices may be an important step towards new silicon memory chips”
The technology has promising applications beyond memory storage. The team are also exploring using the resistance properties of their material not just for use in memory but also as a computer processor.
The work was funded by the Engineering and Physical Sciences Research Council.
Notes for Editors
1. For more information or to interview Dr Tony Kenyon, please contact Clare Ryan in the UCL Media Relations Office on tel: +44 (0)20 3108 3846, mobile: +44 07747 565 056, out of hours +44 (0)7917 271 364, e-mail: clare.ryan@ucl.ac.uk.
2. ‘Resistive switching in silicon suboxide films” is published online in the Journal of Applied Physics. The paper is available for download here: http://jap.aip.org/resource/1/japiau/v111/i7/p074507_s1
3. Journalists can also obtain copies of the paper by contacting UCL Media Relations.
4. Images of the silicon chip described here are available to journalists on request from UCL Media Relations.
About UCL (University College London)
Founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. We are among the world’s top universities, as reflected by performance in a range of international rankings and tables. UCL currently has 24,000 students from almost 140 countries, and more than 9,500 employees. Our annual income is over £800 million.
www.ucl.ac.uk | Follow us on Twitter @uclnews
About UCLB
UCLB is a leading technology transfer company that supports and commercialises research and innovations arising from UCL, one of the UK’s top research-led universities. UCLB has a successful track record and a strong reputation for identifying and protecting promising new technologies and innovations from UCL academics. It invests directly in development projects to maximise the potential of the research and manages the commercialisation process of technologies from the laboratory to market. UCLB supports UCL’s Grand Challenges of increasing UCL’s positive impact on and contribution to Global Health, Sustainable Cities, Intercultural Interaction and Human Wellbeing. For further information, please visit www.uclb.com
Contact: Clare Ryan
clare.ryan@ucl.ac.uk
44-203-108-3846
University College London
Computing experts unveil superefficient ‘inexact’ chip
May 17, 2012
Researchers have unveiled an “inexact” computer chip that challenges the industry’s dogmatic 50-year pursuit of accuracy. The design improves power and resource efficiency by allowing for occasional errors. Prototypes unveiled this week at the ACM International Conference on Computing Frontiers in Cagliari, Italy, are at least 15 times more efficient than today’s technology.
The research, which earned best-paper honors at the conference, was conducted by experts from Rice University in Houston, Singapore’s Nanyang Technological University (NTU), Switzerland’s Center for Electronics and Microtechnology (CSEM) and the University of California, Berkeley.
“It is exciting to see this technology in a working chip that we can measure and validate for the first time,” said project leader Krishna Palem, who also serves as director of the Rice-NTU Institute for Sustainable and Applied Infodynamics (ISAID). “Our work since 2003 showed that significant gains were possible, and I am delighted that these working chips have met and even exceeded our expectations.”
ISAID is working in partnership with CSEM to create new technology that will allow next-generation inexact microchips to use a fraction of the electricity of today’s microprocessors.
“The paper received the highest peer-review evaluation of all the Computing Frontiers submissions this year,” said Paolo Faraboschi, the program co-chair of the ACM Computing Frontiers conference and a distinguished technologist at Hewlett Packard Laboratories. “Research on approximate computation matches the forward-looking charter of Computing Frontiers well, and this work opens the door to interesting energy-efficiency opportunities of using inexact hardware together with traditional processing elements.”
The concept is deceptively simple: Slash power use by allowing processing components — like hardware for adding and multiplying numbers — to make a few mistakes. By cleverly managing the probability of errors and limiting which calculations produce errors, the designers have found they can simultaneously cut energy demands and dramatically boost performance.
One example of the inexact design approach is “pruning,” or trimming away some of the rarely used portions of digital circuits on a microchip. Another innovation, “confined voltage scaling,” trades some performance gains by taking advantage of improvements in processing speed to further cut power demands.
In their initial simulated tests in 2011, the researchers showed that pruning some sections of traditionally designed microchips could boost performance in three ways: The pruned chips were twice as fast, used half as much energy and were half the size. In the new study, the team delved deeper and implemented their ideas in the processing elements on a prototype silicon chip.
“In the latest tests, we showed that pruning could cut energy demands 3.5 times with chips that deviated from the correct value by an average of 0.25 percent,” said study co-author Avinash Lingamneni, a Rice graduate student. “When we factored in size and speed gains, these chips were 7.5 times more efficient than regular chips. Chips that got wrong answers with a larger deviation of about 8 percent were up to 15 times more efficient.”
Project co-investigator Christian Enz, who leads the CSEM arm of the collaboration, said, “Particular types of applications can tolerate quite a bit of error. For example, the human eye has a built-in mechanism for error correction. We used inexact adders to process images and found that relative errors up to 0.54 percent were almost indiscernible, and relative errors as high as 7.5 percent still produced discernible images.”
Palem, the Ken and Audrey Kennedy Professor of Computing at Rice, who holds a joint appointment at NTU, said likely initial applications for the pruning technology will be in application-specific processors, such as special-purpose “embedded” microchips like those used in hearing aids, cameras and other electronic devices.
The inexact hardware is also a key component of ISAID’s I-slate educational tablet. The low-cost I-slate is designed for Indian classrooms with no electricity and too few teachers. Officials in India’s Mahabubnagar District announced plans in March to adopt 50,000 I-slates into middle and high school classrooms over the next three years.
The hardware and graphic content for the I-slate are being developed in tandem. Pruned chips are expected to cut power requirements in half and allow the I-slate to run on solar power from small panels similar to those used on handheld calculators. Palem said the first I-slates and prototype hearing aids to contain pruned chips are expected by 2013.
Contact: Jade Boyd
jadeboyd@rice.edu
713-348-6778
Rice University
New protocol enables wireless and secure biometric acquisition with web services
May 5, 2012
Researchers at the National Institute of Standards and Technology (NIST) have developed and published a new protocol for communicating with biometric sensors over wired and wireless networks – using some of the same technologies that underpin the web.
The new protocol, called WS-Biometric Devices (WS-BD), allows desktops, laptops, tablets and smartphones to access sensors that capture biometric data such as fingerprints, iris images and face images using web services. Web services themselves are not new; for example, video-on-demand services use web services to stream videos to mobile devices and televisions.
The WS-Biometric Devices protocol will greatly simplify setting up and maintaining secure biometric systems for verifying identity because such biometric systems will be easier to assemble with interoperable components compared to current biometrics systems that generally have proprietary device-specific drivers and cables. WS-BD enables interoperability by adding a device-independent web-services layer in the communication protocol between biometric devices and systems.
Remember the last time you bought a new computer only to learn that you then had to upgrade your printer and find the appropriate drivers? For system owners, the difficulty of upgrading devices on a biometric system can mean significant costs. Using the WS-BD protocol eliminates that problem.
“This would be useful to many organizations that house biometric systems, including border control and customs agencies,” explained computer scientist Kevin Mangold. Using current biometric systems, when one biometric sensor breaks, it can be expensive and time-consuming to find a replacement because manufacturers often change product lines and phase out previous generation devices. A few broken devices could entail having to rebuild the entire system, upgrade devices and drivers that may be incompatible with host operating systems, and retrain personnel, he said.
Biometrics are playing an increasing role in security, access control and identity management. And their use is expanding – for example, some theme parks use biometrics for access control. Fingerprints are used in conjunction with passwords for computer security. Many jobs require employees to provide biometrics; using WS-BD equipment could potentially reduce costs by facilitating interoperability in biometrics devices.
A 2010 National Academies study, Biometric Recognition: Challenges and Opportunities, recognized that “Biometric systems should be designed to anticipate the development and adoption of new advances and standards, modularizing components that are likely to become obsolete, such as biometric sensors, and matcher systems, so that they can be easily replaced.”
NIST researchers recognized this need several years ago and developed a solution with the support of the Department of Homeland Security Science and Technology Directorate, the Federal Bureau of Investigation’s Biometric Center of Excellence and NIST’s Comprehensive National Cybersecurity Initiative. NIST also is working with industry through the Small Business Innovation Research Program to help bring these plug-and-play biometric devices to market.
Two NIST researchers recently demonstrated the NIST-developed WS-BD system in their lab using a tablet and two biometric sensors (see video). A tap on the tablet signals the web-enabled fingerprint sensor to capture four fingerprints from the individual whose hand is on the scanner and send it back to the tablet. A tap on another button controls a camera to take a photo for facial recognition.
The new protocol, Specification for WS-Biometric Devices (NIST Special Publication 500-288) can be found at www.nist.gov/manuscript-publication-search.cfm?pub_id=910334. Additional information on this and related projects can be found at http://bws.nist.gov.
While this is a final document, NIST welcomes your feedback, comments and questions for considerations for future updates. Send your comments to the WS-BD teams by emailing 500-288comments@nist.gov.
Watch presentation on YouTube at http://www.youtube.com/watch?v=VTxIA-wkmo0&feature=player_embedded
Contact: Evelyn Brown
evelyn.brown@nist.gov
301-975-5661
National Institute of Standards and Technology (NIST)
First ‘microsubmarines’ designed to help clean up oil spills
May 2, 2012
Scientists are reporting development and successful testing of the first self-propelled “microsubmarines” designed to pick up droplets of oil from contaminated waters and transport them to collection facilities. The report concludes that these tiny machines could play an important role in cleaning up oil spills, like the 2010 Deepwater Horizon incident in the Gulf of Mexico. It appears in the journal ACS Nano.
Joseph Wang and colleagues explain that different versions of microengines have been developed, including devices that could transport medications through the bloodstream to diseased parts of the body. But no one has ever shown that these devices – which are about 10 times smaller than the width of a human hair – could help clean up oil spills. There is an urgent need for better ways of separating oil from water in the oceans and inside factories to avoid releasing oil-contaminated water to the environment. Wang’s team developed so-called microsubmarines, which require very little fuel and move ultrafast, to see whether these small engines could help clean up oil.
Tests showed that the cone-shaped microsubmarines can collect droplets of olive oil and motor oil in water and transport them through the water. The microsubs have a special surface coating, which makes them “superhydrophobic,” or extremely water-repellent and oil-absorbent. “These results demonstrate the potential of the superhydrophobic-modified microsubmarines for facile, rapid and highly efficient collection of oils in oil-contaminated water samples,” say the researchers.
The authors acknowledge funding from the National Science Foundation, NATO Science for Peace and Security Program, Spanish MICINN, Beatriu de Pinós (Government of Catalonia) and University of Alcalá (Madrid).
The American Chemical Society is a nonprofit organization chartered by the U.S. Congress. With more than 164,000 members, ACS is the world’s largest scientific society and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.
Contact: Michael Bernstein
m_bernstein@acs.org
202-872-6042
American Chemical Society
Redefining time
April 30, 2012
Atomic clocks based on the oscillations of a cesium atom keep amazingly steady time and also define the precise length of a second. But cesium clocks are no longer the most accurate. That title has been transferred to an optical clock housed at the U.S. National Institute of Standards and Technology (NIST) in Boulder, Colo. that can keep time to within 1 second in 3.7 billion years. Before this newfound precision can redefine the second, or lead to new applications like ultra-precise navigation, the system used to communicate time around the globe will need an upgrade. Recently scientists from the Max Planck Institute of Quantum Optics, in the south of Germany, and the Federal Institute of Physical and Technical Affairs in the north have taken a first step along that path, successfully sending a highly accurate clock signal across the many hundreds of kilometers of countryside that separate their two institutions.
The researchers will present their finding at Conference on Lasers and Electro Optics (CLEO: 2012), taking place May 6 -11 in San Jose, Calif.
“Over the last decade a new kind of frequency standard has been developed that is based on optical transitions, the so-called optical clock,” says Stefan Droste, a researcher at the Max Planck Institute of Quantum Optics. The NIST optical clock, for example, is more than one hundred times more accurate than the cesium clock that serves as the United States’ primary time standard.
Extremely precise time keeping – and the ability to communicate the world time standard across long distances – is vital to myriad applications, including in navigation, international commerce, seismology, and fundamental quantum physics. Unfortunately, the satellite-based links currently used to communicate that standard are not up to the task of transmitting such a stable signal, so the second retains its less precise measure. Optical fiber links could work better, but had previously been tested only over short distances, such as those separating buildings on the same campus or within the same urban area.
“The average distance between institutes that operate frequency standards in Europe is on the order of a few thousand kilometers,” notes Droste. “Spanning these great distances with an optical link is challenging not only because of the additional degradation of the transferred signal, but also because multiple signal conditioning stations need to be installed and operated continuously along the link path.” Droste and his colleagues were able to overcome the challenges by installing nine signal amplifiers along a 920-kilometer-long fiber link. They successfully transferred a frequency signal with more than 10 times the accuracy than would be required for today’s most precise optical clocks.
CLEO: 2012 presentation CTh4A.1. “Optical Frequency Transfer via 920 km Fiber Link with 10−19 Relative Accuracy” by Stefan Droste et al. is at 4:30 p.m. on Thursday, May 10 in the San Jose Convention Center.
Press Registration
A Press Room for credentialed press and analysts will be located on-site in the San Jose Convention Center, May 6 – May 11. Media interested in attending the conference should register on the CLEO website or contact Angela Stark at 202.416.1443, astark@osa.org.
About CLEO
With a distinguished history as the industry’s leading event on laser science, the Conference on Lasers and Electro-Optics (CLEO) is where laser technology was first introduced. CLEO unites the field of lasers and electro-optics by bringing together all aspects of laser technology, with content stemming from basic research to industry application. CLEO: Expo showcases the latest products and applications from more than 300 participating companies from around the world, providing hands-on demonstrations of the latest market innovations and applications. The Expo also offers valuable on-floor programming, including Market Focus and the Technology Transfer program.
Sponsored by the American Physical Society’s (APS) Laser Science Division, the Institute of Electronic Engineers (IEEE) Photonics Society and the Optical Society (OSA), CLEO provides the full range of critical developments in the field, showcasing the most significant milestones from laboratory to marketplace. With an unparalleled breadth and depth of coverage, CLEO connects all of the critical vertical markets in lasers and electro-optics. For more information, visit the conference’s website at www.cleoconference.org.
Contact: Angela Stark
astark@osa.org
202-416-1443
Optical Society of America
Quantum computer built inside a diamond
April 4, 2012
Diamonds are forever – or, at least, the effects of this diamond on quantum computing may be.
A team that includes scientists from USC has built a quantum computer in a diamond, the first of its kind to include protection against “decoherence” – noise that prevents the computer from functioning properly.
The demonstration shows the viability of solid-state quantum computers, which – unlike earlier gas- and liquid-state systems – may represent the future of quantum computing because they can be easily scaled up in size. Current quantum computers are typically very small and – though impressive – cannot yet compete with the speed of larger, traditional computers.
The multinational team included USC Professor Daniel Lidar and USC postdoctoral researcher Zhihui Wang, as well as researchers from the Delft University of Technology in the Netherlands, Iowa State University and the University of California, Santa Barbara. Their findings will be published on April 5 in Nature.
The team’s diamond quantum computer system featured two quantum bits (called “qubits”), made of subatomic particles.
As opposed to traditional computer bits, which can encode distinctly either a one or a zero, qubits can encode a one and a zero at the same time. This property, called superposition, along with the ability of quantum states to “tunnel” through energy barriers, will some day allow quantum computers to perform optimization calculations much faster than traditional computers.
Like all diamonds, the diamond used by the researchers has impurities – things other than carbon. The more impurities in a diamond, the less attractive it is as a piece of jewelry, because it makes the crystal appear cloudy.
The team, however, utilized the impurities themselves.
A rogue nitrogen nucleus became the first qubit. In a second flaw sat an electron, which became the second qubit. (Though put more accurately, the “spin” of each of these subatomic particles was used as the qubit.)
Electrons are smaller than nuclei and perform computations much more quickly, but also fall victim more quickly to “decoherence.” A qubit based on a nucleus, which is large, is much more stable but slower.
“A nucleus has a long decoherence time – in the milliseconds. You can think of it as very sluggish,” said Lidar, who holds a joint appointment with the USC Viterbi School of Engineering and the USC Dornsife College of Letters, Arts and Sciences.
Though solid-state computing systems have existed before, this was the first to incorporate decoherence protection – using microwave pulses to continually switch the direction of the electron spin rotation.
“It’s a little like time travel,” Lidar said, because switching the direction of rotation time-reverses the inconsistencies in motion as the qubits move back to their original position.
The team was able to demonstrate that their diamond-encased system does indeed operate in a quantum fashion by seeing how closely it matched “Grover’s algorithm.”
The algorithm is not new – Lov Grover of Bell Labs invented it in 1996 – but it shows the promise of quantum computing.
The test is a search of an unsorted database, akin to being told to search for a name in a phone book when you’ve only been given the phone number.
Sometimes you’d miraculously find it on the first try, other times you might have to search through the entire book to find it. If you did the search countless times, on average, you’d find the name you were looking for after searching through half of the phone book.
Mathematically, this can be expressed by saying you’d find the correct choice in X/2 tries – if X is the number of total choices you have to search through. So, with four choices total, you’ll find the correct one after two tries on average.
A quantum computer, using the properties of superposition, can find the correct choice much more quickly. The mathematics behind it are complicated, but in practical terms, a quantum computer searching through an unsorted list of four choices will find the correct choice on the first try, every time.
Though not perfect, the new computer picked the correct choice on the first try about 95 percent of the time – enough to demonstrate that it operates in a quantum fashion.
This research was funded by the National Science Foundation and the US Army Research Office’s Multidisciplinary University Research Initiative.
Contact: Robert Perkins
perkinsr@usc.edu
213-740-9226
University of Southern California
Honeycombs of magnets could lead to new type of computer processing
March 30, 2012
Scientists have taken an important step forward in developing a new material using nano-sized magnets that could ultimately lead to new types of electronic devices, with greater capacity than is currently feasible, in a study published today in the journal Science.
Many modern data storage devices, like hard disk drives, rely on the ability to manipulate the properties of tiny individual magnetic sections, but their overall design is limited by the way these magnetic ‘domains’ interact when they are close together.
Now, researchers from Imperial College London have demonstrated that a honeycomb pattern of nano-sized magnets, in a material known as spin ice, introduces competition between neighbouring magnets, and reduces the problems caused by these interactions by two-thirds. They have shown that large arrays of these nano-magnets can be used to store computable information. The arrays can then be read by measuring their electrical resistance.
The scientists have so far been able to ‘read’ and ‘write’ patterns in the magnetic fields, and a key challenge now is to develop a way to utilise these patterns to perform calculations, and to do so at room temperature. At the moment, they are working with the magnets at temperatures below minus 223oC.
Research author Dr Will Branford and his team have been investigating how to manipulate the magnetic state of nano-structured spin ices using a magnetic field and how to read their state by measuring their electrical resistance. They found that at low temperatures (below minus 223oC) the magnetic bits act in a collective manner and arrange themselves into patterns. This changes their resistance to an electrical current so that if one is passed through the material, this produces a characteristic measurement that the scientists can identify.
The scientists have so far been able to ‘read’ and ‘write’ patterns at room temperature. However, at the moment the collective behaviour is only seen at temperatures below minus 223oC. A key challenge now is to develop a way to utilise these patterns to perform calculations, and to do so at room temperature.
Current technology uses one magnetic domain to store a single bit of information. The new finding suggests that a cluster of many domains could be used to solve a complex computational problem in a single calculation. Computation of this type is known as a neural network, and is more similar to how our brains work than to the way in which traditional computers process information.
Dr Branford, who is an EPSRC Career Acceleration Fellow in the Department of Physics at Imperial College London, said: “Electronics manufacturers are trying all the time to squeeze more data into the same devices, or the same data into a tinier space for handheld devices like smart phones and mobile computers. However, the innate interaction between magnets has so far limited what they can do. In some new types of memory, manufacturers try to avoid the limitations of magnetism by avoiding using magnets altogether, using things like ferroelectric (flash) memory, memristors or antiferromagnets instead. However, these solutions are slow, expensive or hard to read out. Our philosophy is to harness the magnetic interactions, making them work in our favour.”
Although today’s research represents a key step forward, the researchers say there are many hurdles to overcome before scientists will be able to create prototype devices based on this technique such as developing an algorithm to control the computation. The nature of this algorithm will determine whether the room temperature state can be used or if the low temperature collective behaviour is required. However, they are optimistic that if these challenges can be tackled successfully, new technology using magnetic honeycombs might be available in ten to fifteen years.
In experiments, Dr Branford applied an electrical current across a continuous honeycomb mesh, made from cobalt magnetic bars each 1 micrometer long and 100 nanometres wide, and covering an area 100 square micrometers (as pictured). A single unit of the honeycomb mesh is like three bar magnets meeting in the centre of a triangle. There is no way to arrange them without having either two north poles or two south poles touching and repelling each other, this is called a ‘frustrated’ magnetic system. In a single triangular unit there are six ways to arrange the magnets such that they have exactly the same level of frustration, and as you increase the number of triangular units in the honeycomb, the number of possible arrangements of magnets increases exponentially, increasing the complexity of possible patterns.
Previous studies have shown that external magnetic fields can cause the magnetic domain of each bar to change state. This in turn affects the interaction between that bar and its two neighbouring bars in the honeycomb, and it is this pattern of magnetic states that Dr Branford says could be computer data.
Dr Branford said: “The strong interaction between neighbouring magnets allows us to subtly affect how the patterns form across the honeycomb. This is something we can take advantage of to compute complex problems because many different outcomes are possible, and we can differentiate between them electronically. Our next big challenge is to make an array of nano-magnets that can be ‘programmed’ without using external magnetic fields.”
Contact: Simon Levey
s.levey@imperial.ac.uk
44-020-759-46702
Imperial College London
A camera that peers around corners
March 21, 2012
In December, MIT Media Lab researchers caused a stir by releasing a slow-motion video of a burst of light traveling the length of a plastic bottle. But the experimental setup that enabled that video was designed for a much different application: a camera that can see around corners.
In a paper appearing this week in the journal Nature Communications, the researchers describe using their system to produce recognizable 3-D images of a wooden figurine and of foam cutouts outside their camera’s line of sight. The research could ultimately lead to imaging systems that allow emergency responders to evaluate dangerous environments or vehicle navigation systems that can negotiate blind turns, among other applications.
The principle behind the system is essentially that of the periscope. But instead of using angled mirrors to redirect light, the system uses ordinary walls, doors or floors – surfaces that aren’t generally thought of as reflective.
The system exploits a device called a femtosecond laser, which emits bursts of light so short that their duration is measured in quadrillionths of a second. To peer into a room that’s outside its line of sight, the system might fire femtosecond bursts of laser light at the wall opposite the doorway. The light would reflect off the wall and into the room, then bounce around and re-emerge, ultimately striking a detector that can take measurements every few picoseconds, or trillionths of a second. Because the light bursts are so short, the system can gauge how far they’ve traveled by measuring the time it takes them to reach the detector.
The system performs this procedure several times, bouncing light off several different spots on the wall, so that it enters the room at several different angles. The detector, too, measures the returning light at different angles. By comparing the times at which returning light strikes different parts of the detector, the system can piece together a picture of the room’s geometry.
Off the bench
Previously, femtosecond lasers had been used to produce extremely high-speed images of biochemical processes in a laboratory setting, where the trajectories of the laser pulses were carefully controlled. “Four years ago, when I talked to people in ultrafast optics about using femtosecond lasers for room-sized scenes, they said it was totally ridiculous,” says Ramesh Raskar, an associate professor at the MIT Media Lab, who led the new research.
Andreas Velten, a former postdoc in Raskar’s group who is now at the University of Wisconsin at Madison, conducted the experiments reported in Nature Communications using hardware in the lab of MIT chemist Moungi Bawendi, who’s collaborating on the project. Velten fired femtosecond bursts of laser light at an opaque screen, which reflected the light onto objects suspended in front of another opaque panel standing in for the back wall of a room.
The data collected by the ultrafast sensor were processed by algorithms that Raskar and Velten developed in collaboration with Otkrist Gupta, a graduate student in Raskar’s group; Thomas Willwacher, a mathematics postdoc at Harvard University; and Ashok Veeraraghavan, an assistant professor of electrical engineering and computer science at Rice University. The 3-D images produced by the algorithms were blurry but easily recognizable.
Raskar envisions that a future version of the system could be used by emergency responders – firefighters looking for people in burning buildings or police determining whether rooms are safe to enter – or by vehicle navigation systems, which could bounce light off the ground to look around blind corners. It could also be used with endoscopic medical devices, to produce images of previously obscure regions of the human body.
In its work so far, Raskar says, his group has discovered that the problem of peering around a corner has a great deal in common with that of using multiple antennas to determine the direction of incoming radio signals. Going forward, Raskar hopes to use that insight to improve the quality of the images the system produces and to enable it to handle visual scenes with a lot more clutter.
Written by Larry Hardesty, MIT News Office
Contact: Caroline McCall
cmccall5@mit.edu
Massachusetts Institute of Technology
Is bioethanol a more environmentally benign option to petroleum-derived fuels?
February 25, 2012
A life cycle assessment of growing crops for fuel as opposed to refining and using fossil fuels has revealed that substitution of gasoline by bioethanol converted from energy crops has considerable potential for rendering our society more sustainable, according to a Japanese study published in the International Journal of Foresight and Innovation Policy.
Kiyotada Hayashi of the National Agriculture and Food Research Organisation in Tsukuba and colleagues explain how biomass derived from sugarcane, sugar beet and other crops, has emerged as one of the most promising renewable energy sources. Some observers suggest that it makes an excellent substitute for oil-derived fuels and it is being used widely in certain parts of the world already. However, there are concerns about land use and the overall life-cycle impact on raising fuel crops and the energy required to process and exploit biomass compared with fossil fuels. The Japanese team has now put to rest some of those concerns in a life cycle assessment of energy crop production for bioethanol in Japan.
The team hoped to clarify the potential of biomass utilisation while taking into account the cumulative fossil energy demand and climate change impact. They looked at two scenarios: one in which cultivation technologies improves and breeding of new crop varieties is made possible. The second scenario looked at how the establishment of regional biomass utilisation systems that used biomass resources from various industries might function mutually and effectively and again reduce fossil fuel demand and reduce carbon emissions.
“We proved that the improvement in cultivation technologies and the establishment of regional biomass utilisation systems have large potential for saving fossil fuel resources and reducing greenhouse gas emissions,” the team concludes. The researchers concede that their results largely depend on scenarios including the lifetime and coverage area of agricultural machinery, and types of biomass utilisation, but point out that the substitution of gasoline with bioethanol converted from energy crops has considerable potential for rendering our society more sustainable.
“Life cycle assessment of energy crop production with special attention to the establishment of regional biomass utilisation systems” in Int. J. Foresight and Innovation Policy, 2012, 8, 143-172
Contact: Kiyotada Hayashi
hayashi@affrc.go.jp
81-298-388-850
Inderscience Publishers
Computer scientist developing intersections of the future with fully autonomous vehicles
February 20, 2012
Intersections of the future will not need stop lights or stop signs, but will look like a somewhat chaotic flow of driverless, autonomous cars slipping past one another as they are managed by a virtual traffic controller, says computer scientist Peter Stone.
“A future where sitting in the backseat of the car reading our newspaper while it drives us effortlessly through city streets and intersections is not that far away,” says Stone, a professor of computer science at The University of Texas at Austin.
Stone’s research focuses on creating artificially intelligent (AI) computing systems, and he is developing some of the systems that are needed to make autonomous driving a reality. For example, Stone and his students created an autonomous car, named Marvin, in cooperation with Austin Robot Technology that competed in the 2007 DARPA Urban Challenge competition.
This week, Stone presents his research on autonomous intersection management at the American Association for the Advancement of Science (AAAS) annual meeting in Vancouver, British Columbia.
“Computers can already fly a passenger jet much like a trained human pilot, but people still face the dangerous task of driving automobiles,” he says. “Vehicles are being developed that will be able to handle most of the driving tasks themselves. But once autonomous vehicles become popular, we need to coordinate those vehicles on the streets.”
To that end, Stone is developing virtual intersection systems that will make auto travel safer and faster.
In his newest system, AI driver agents (the autonomous vehicles) “call ahead” and reserve space and a time at an intersection. Then an arbiter agent, called an “intersection manager,” approves the request, and the vehicles move through. There is little stopped traffic. (Watch a simulation video: http://youtu.be/j0fYERuJ2vw)
For now, the action takes place mainly as a simulation on a computer, or with a single real car (for example, Marvin) interacting with many other simulated cars. But Stone says the day is near when we’ll start seeing autonomous vehicles on the streets, and the benefits of controlling the cars – and traffic – will be realized.
Contact: Peter Stone
pstone@cs.utexas.edu
512-471-9796
University of Texas at Austin