#See through Walls by the Glow of Your Wi-fi It used to be that a bad guy besieged by police could just shoot out the lights and hide in the dark.
As if it weren enough that today cornered malefactors have to worry about night vision goggles, tomorrow thugs may also have to worry about the soft radio glow of wireless routers and mobile communications towers.
Researchers at University college London (UCL) have devised a system for detecting the Doppler shifts of ubiquitous Wi-fi
and mobile telephone signals to eepeople moving, even behind masonry walls 25 centimeters thick. The method
which could be useful in situations from hostage-takings to traffic control, won the Engineering Impact Award in the RF and Communications category at this National Instrument NI Week 2015 meeting
(which convened in Austin, Tex.,3-9 august. Other researchersotably Dina Katabi and Fadel Adib of MITAVE built through-wall radars in the household communication bands,
but these are active radars that transmit as well as receive. The UCL technique uses only passive radiationrom Wi-fi routers (using emissions in any of the IEEE 802.11 b, g, n, ac), ambient GSM and LTE mobile signals,
and other sourceso there is nothing to betray the surveillance. The system calculates the positions of hidden target by comparing two signals:
a reference channel, receiving the baseline signal from the Wi-fi access point or other RF source,
and a surveillance channel, which picks up Doppler-shifted waves reflecting from the moving subject.
Tan and company built their igh Doppler resolution passive Wi-fi radaron two multi-frequency, software-defined, FPGA-based transceivers (National Instrumentsusrp,
or Universal Software Radio Peripheral. The system compares the reference and surveillance signals, interprets the very small frequency shifts,
and reveals the hidden subject location and motion. By tweaking the processing parametersncreasing signal-integration time
along with a variety of signal data. The system is described in more detail in a paper that Tan and UCL colleagues Qingchao Chen, Karl Woodbridge,
and Kevin Chetty presented at the 2015 IEEE International Conference on Acoustics, Speech and Signal processing (ICASSP), held 19-24 april in South Brisbane, Australia
#Graphene"Decorated"With Lithium Becomes a Superconductor Graphene is a conductor unlike anything seen before.
promising a new approach to electronics. It even been engineered to act like a semiconductor with a band gap for stopping
and starting the flow of electrons, thus offering an alternative to silicon in electronics. Despite these properties,
and a host of others that seem to sprout up regularly, nobody had been able to make graphene behave as a superconductor, until now.
An international research team from Canada and Germany has been able to demonstrate that graphene can be made to behave as a superconductor
when it doped with lithium atoms. The researchers believe that this new property could lead to a new generation of superconducting nanoscale devices.
Superconductors are materials that conduct electricity without resistance and without dissipating energy. In ordinary materials, electrons repel each other,
but in superconductors the electrons form pairs known as Cooper pairs, which together flow through the material without resistance.
Phonons, the mechanism that facilitates these electronsalliances are vibrations in lattice crystalline structures. Graphene is not naturally a superconductor,
and neither is its three-dimensional sourceraphite. However, it was demonstrated a decade ago that graphite could be induced into behaving like a superconductor.
If it possible with graphite it should be with graphene, right? Other research groups believed
so and developed computer models demonstrating that combining graphene with lithium might do the trick. Lithium, they predicted,
could contribute a lot of phonons to the graphene electrons. In a research paper available on arxiv, the researchers demonstrated in physical experiments that the computer models were indeed correct in their predictions.
Andrea Damascelli at the University of British Colombia in Vancouver, together with collaborators in Europe, grew layers of graphene on silicon-carbide substrates,
then deposited lithium atoms onto the graphene in a vacuum at 8 K, creating a version of graphene known as ecoratedgraphene.
In the testing and measuring of their material the researchers found that the electrons slowed down as they travelled through the lattice,
The key observation was increased that this number of coupled pairs led to superconductivity, which the researchers measured by identifying an energy gap between the material's conducting and nonconducting electrons.
That energy gap is equal to the amount of energy needed to break Cooper pairs. The researchers who demonstrated last year the role phonons played in the superconductivity of graphite and calcium, Patrick Kirchmann and Shuolong Yang of the SLAC National Accelerator Laboratory
believe this latest work could usher in the fabrication of nanoscale superconducting quantum interference devices and single-electron superconductor quantum dots u
#A Driving App That Crowdsources the Weather It a cold day in winter and youe driving on dry pavement when your dashboard flashes a warning:
black ice up ahead. You slow down, engage your four-wheel drive and start watching for other drivers who might not be informed so well as you.
That scene, straight out of the connected car playbook, would seem to require a few more years of public investment in smart roads,
but in fact this very service was announced today. It comes from Inrix, a road-data provider based near Seattle,
and from its partner in the service, Global Weather Corporation. Up until now, Inrix had gathered basic data from hundreds of millions of moving objects throughout the worldostly cell phones
cars and fleet vehiclesnd sold it to fleet operators and car makers like Porsche. Those companies, in turn, typically made it available through smartphone apps or dashboard consoles.
The new service, called INRIX Road Weather, adds data gleaned from the actions of the caror instance,
the switching of its windshield wipershich would imply that it has started to rain. f several cars in a location show that a low temperature is kicking in,
we take in their position from GPS signals, data from our weather partner, and then say that at that spotithin 500 metershere is black ice,
says Steve Banfield, chief marketing officer for Inrix. t a much more focused warning than before,
not only for drivers but for the folks in charge of sanding the roads, safety patrols and law enforcement. he most important data come from a handful of car functions:
the time of day, the GPS coordinates, the temperature outside the car, what the brakes are doing (particularly automatic braking systems),
and whether the fog lights are on. Auxiliary data might include barometric pressure, the temperature of the road itself (taken by infrared sensors), barometric pressure,
and of course the stage of those windshield wipers. e are pioneering the connected car, Banfield says. oday we are alerting a human driver,
but it will be of incredible value to automated driving when that comes. anfield wouldn say how much Inrix charges fleets and car makers,
only that it was a minuscule sum compared to the overall cost of operating a vehicle. he charge for the service will be paid by the OEMS original equipment manufacturers for the first few years;
after that, if customer wants to continue, then he might pay for an extended subscription. i
#Graphene and Perovskite Lead to Inexpensive and Highly Efficient Solar cells Perovskite is the new buzzword in photovoltaics.
And graphene is the buzzword for just about every other high-tech application, including photovoltaics. Now researchers at Hong kong Polytechnic University have combined these two materials to make a semitransparent solar cell capable of power conversion efficiencies around 12 percent, a significant improvement over the roughly 7-percent efficiency of traditional
semitransparent solar cells. The semitransparent design of these solar cells means that they can absorb light from both sides
and could allow them to be used as windows that serve the dual function of letting light into a building
and generating electricity. In the design of the Hong kong researcherssolar cell, the perovskite serves as active layer for harvesting the light,
and the graphene acts as the transparent electrode material. Graphene has long been pursued as a potential replacement for indium tin oxide (ITO) as a transparent electrode material for displays.
Here again, graphene transparency, high conductivity, and potentially low cost seemed attractive to the researchers. The researchers improved on the conductivity of the graphene by coating it with a thin layer of a polymer that also served as an adhesion layer to the perovskite active layer during the lamination process.
The researchers were able to improve the energy conversion capability of the solar cells by employing a multi-layer chemical vapor deposition process in
which the graphene formed the top transparent electrodes. This approach maintained the transparency of the electrodes
while increasing their sheet resistance. A big concern for the researchers was lowering costs. They claim that their solar cells cost less than US$. 06/watt,
which they reckon is more than a 50 percent reduction in the costs of silicon solar cells. They believe that the whole process is ripe for scaling up
because the mechanical flexibility of the graphene enables the possibility of roll-to-roll processing o
#Graphene and Perovskite Lead to Inexpensive and Highly Efficient Solar cells Perovskite is the new buzzword in photovoltaics.
And graphene is the buzzword for just about every other high-tech application, including photovoltaics. Now researchers at Hong kong Polytechnic University have combined these two materials to make a semitransparent solar cell capable of power conversion efficiencies around 12 percent, a significant improvement over the roughly 7-percent efficiency of traditional
semitransparent solar cells. The semitransparent design of these solar cells means that they can absorb light from both sides
and could allow them to be used as windows that serve the dual function of letting light into a building
and generating electricity. In the design of the Hong kong researcherssolar cell, the perovskite serves as active layer for harvesting the light,
and the graphene acts as the transparent electrode material. Graphene has long been pursued as a potential replacement for indium tin oxide (ITO) as a transparent electrode material for displays.
Here again, graphene transparency, high conductivity, and potentially low cost seemed attractive to the researchers. The researchers improved on the conductivity of the graphene by coating it with a thin layer of a polymer that also served as an adhesion layer to the perovskite active layer during the lamination process.
The researchers were able to improve the energy conversion capability of the solar cells by employing a multi-layer chemical vapor deposition process in
which the graphene formed the top transparent electrodes. This approach maintained the transparency of the electrodes
while increasing their sheet resistance. A big concern for the researchers was lowering costs. They claim that their solar cells cost less than US$. 06/watt,
which they reckon is more than a 50 percent reduction in the costs of silicon solar cells. They believe that the whole process is ripe for scaling up
because the mechanical flexibility of the graphene enables the possibility of roll-to-roll processing i
#Japanese Paper Cutting Trick for Moving Solar cells To maximize the amount of electricity that solar cells generate,
solar panels can be tilted to track the position of the sun over the course of a day.
Conventional solar trackers can increase yearly energy generation by 20 to 40 percent, but they can be costly,
heavy and bulky, limiting their widespread implementation. Now materials scientist Max Shtein and his colleagues at the University of Michigan at Ann arbor have developed novel solar cells that integrate tracking into their design.
The design involves a variation of origami known as kirigami which uses both folding and cutting to create unique structures.
They detailed their findings in the 8 september online edition of the journal Nature Communications. The scientists cut kirigami designs into a 3-micron-thick flexible crystalline gallium arsenide solar cells mounted on plastic sheets.
A solar cell array of this type can tilt in three dimensions in a highly controllable manner
when its edges are tugged. So a quick pull can make it flex so that it is at the best angle for catching rays.
The researchers found that their new devices could generate roughly as much power as solar cells mounted on conventional trackers.
Moreover the kirigami trackers proved to be electrically and mechanically robust, with no appreciable decrease in performance after more than 300 cycles of activity.
Shtein and his colleagues suggest that kirigami solar panels could be simple, inexpensive and lightweight, and have widespread rooftop, mobile,
and spaceborne applications. They added that kirigami systems might also be phased useful for array radar and optical beam steering.
The scientists are now exploring whether mounting solar cells onto more durable materials such as spring steel could make kirigami systems even more robust t
#Graphene's Killer App? Measuring Electrical resistance Graphene merits in electronic devices and as a light bulb coating are still being debated.
But new results suggest the atom-thick carbon sheet has one clear advantage: precise but practical calibrations of electrical resistance.
This might seem like a minor use for the world most celebrated wonder material, but it one that sits at the very base of the electrical engineering pyramid.
A more practical calibration could help national standards laboratories and industries that depend on those standards.
It may also help disseminate the International system of Units (SI), which could be overhauled as early as 2018.
The most exacting metrology laboratories calibrate their electrical units based on quantum mechanical phenomena. The ohm, the SI unit of electrical resistance, is calibrated by taking advantage of the quantum Hall effect.
The Hall effect occurs when a magnetic field is applied perpendicular to the flow of current. The resulting force on electrons causes them to migrate to the side,
which in turn raises a voltage perpendicular to the flow of current. In the quantum version of the Hall effect,
which occurs in a thin layer of material, the voltage and resulting resistance are uantizedand so take on discrete integer values.
Conveniently, the quantum Hall resistance is expected to be completely independent of the kind of device that built.
Instead it depends only on two unvarying constants of nature: the fundamental charge of the electron and a quantum mechanical measure dubbed the Planck constant.
Unfortunately, the physical conditions required to take advantage of the quantum resistance standard are exacting. State-of-the-art measurements,
which are taken using a device made of thin layers of gallium arsenide and aluminum gallium arsenide, can require a 10-Tesla magnetic field (and so a massive superconducting magnet) and temperatures within a few degrees of absolute zero.
Researchers have suspected long that the unique behavior of electrons in graphene, namely the big spacing between electron energy levels when the material is exposed to a magnetic field,
could be exploited to produce precise measurements of resistance under less extreme physical conditions. Several recent results support that idea.
In August, Jan-Theodoor Janssen at the UK National Physical Laboratory and colleagues reported a way to build a graphene resistance standard that can operate at a higher temperature and lower magnetic field.
This week, a team based at France National Metrology and Testing Laboratory and various departments at the National Center for Scientific research extended those operational conditions even further.
The french team constructed its resistance device from a high-quality sheet of graphene grown on a silicon carbide wafer.
The resulting 100-by-420-micrometer all barcontained a source and drain to raise a voltage across the device
The team found they could measure resistance with a level of accuracy rivaling those yielded by gallium arsenide devices,
but with a magnetic field one-third as strong, with a temperature as high as 10 Kelvin,
The french team wrote this week this week in Nature Nanotechnology. Graphene could also help bring about the realization of a simplified ampere, one of the seven SI base units.
#Peering Into Nanoparticles One at a time Reveals Hidden World Imagine you could single out individuals in a large group
This is essentially what researchers at Chalmers University in Sweden have been able to achieve with a new microscopy technique that is capable of looking at a single nanoparticle rather than just a mass of them all clumped together. e were able to show that you gain deeper insights into the physics
of how nanomaterials interact with molecules in their environment by looking at the individual nanoparticle as opposed to looking at many of them at the same time,
which is what is done usually, said Associate professor Christoph Langhammer, who led the project, in a press release.
The researchers applied the experimental spectroscopy technique to examine hydrogen absorption in single palladium nanoparticles.
despite various nanoparticles having the same size and shape, they would absorb hydrogen at pressures as different as 40 millibars.
this observation could help lead to more sensitive hydrogen sensors for detecting leaks in fuel-cell-powered vehicles. ne main challenge
when working on hydrogen sensors is to design materials whose response to hydrogen is as linear and reversible as possible.
While others have been able to image single nanoparticles previously, those efforts came at a rather high cost of heating the nanoparticles up,
or impacting them in some other way that eliminates the ability to observe them accurately. hen studying individual nanoparticles you have to send some kind of probe to ask the particle hat are you doing?
said Langhammer. his usually means focusing a beam of high-energy electrons or photons or a mechanical probe onto a very tiny volume.
You then quickly get very high energy densities, which might perturb the process you want to look at.
so that it is possible to study nanoparticles one at a time in their actual environments. This ability to observe nanoparticles outside the lab could prove to be a key development for studies on the impact of nanoparticles in the environment e
#An Electric car Heater Can't Be Too Thin or Too Economical Just about every electrical device seems to want to slim down to a thin filmf possible,
one that includes carbon nanotubes. Now Fraunhofer has accomplished both feats, and with the most basic device imaginable:
a heating element. It is very thin and very economical with power. Its first application will likely be as a heater in an electric car,
which, unlike conventional vehicles, can exploit the warmth of air that been passed over an internal combustion engine.
But standard car heaters, which use a matrix with embedded copper wire (often in seats or in the steering wheel), are power-hungry.
That why today drivers of e-cars must either shiver or drain their car already stressed-out batteries. n the most unfavorable case,
you can only drive half the usual distance with the carwhen using the heater, says Serhat Sahakalkan,
who managing the project for Fraunhofer lab in Stuttgart. The idea is to mix nanotubes into a fluid to create a slurry,
lay down a film just a few micrometers thick on a suitable substrate, and run a current through it.
The heat-generating resistance comes mainly from the passage of current through gaps between the nanotubes.
Because the tubes conduct heat so well, they store very little of it, and thus can begin to radiate comforting infrared rays right away.
That feature would be particularly welcome during short trips. And, because the tubes form a vast network
a local defect wouldn shut down operation the way it would in a heater that used copper wire.
Right now, Fraunhofer is putting the film on small panels that can be glued to the inside of a car door,
#3-D Printing Software Turns Heart Scans into Surgical Models A new 3-D printing system can transform medical scans of a patient heart into a physical models that help
plan surgeries. The efficient system relies on a computer algorithm that requires just a pinch of human guidance to figure out a patient heart structure from MRI scans.
The process begins with an MRI scan of a patient heart that shows the organ as hundreds of cross-sectional slices.
The new software developed by MIT and the Boston Children Hospital, can correctly identify an individual heart anatomical structures by following the lead of a human expert who interprets a small patch equivalent to just one-ninth of the area of each cross section, according to an MIT press release.
One of the best results came from a human expert interpreting just 14 patches and allowing the computer algorithm to infer the rest of the patient heart structure across the rest of the MRI scan 200 cross sections.
The software results were in agreement with human experts interpreting all 200 cross sections 90 percent of the time.
A few tweaks allowed the egmentationor digital recreation of a virtual 3-D heart model. think that
if somebody told me that I could segment the whole heart from eight slices out of 200,
said Polina Golland, a professor of electrical engineering and computer science at MIT and leader of the project,
The group worked with high-precision MRI scans developed by Medhi Moghari, a physicist at Boston Children Hospital.
Interpreting all the features of 200 such highly-detailed cross sections would typically take human experts between 8 and 10 hours.
But the new software from a team led by Danielle Pace, an MIT graduate student in electrical engineering and computer science, managed to create a fairly accurate digital 3-D model of each patient heart in just an hour.
The 3-D printing process takes several additional hours. The researchers plan to report on their system at the International Conference on Medical Image Computing and Computer Assisted Intervention in October.
They hope to improve the software accuracy by examining patches that appear in several MRI cross sections.
Seven cardiac surgeons at Boston Children Hospital will also test the usefulness of 3-D printed heart models in a clinical study this fall.
They will draw up surgical plans for 10 patients who have undergone already surgery at Boston Children hospital
and compare the plans with the documented surgeries that were performed. Such surgical plans will either be based on physical 3-D printed models or virtual 3-D models, with the models based on either human expertise or the computer software.
Virtual models of hearts have already proven their worth in basic research. But separate clinical trials aim to test how a personalized computer model for each individual patient could improve medical care,
as previously reported by Natalia Trayanova for IEEE Spectrum. The MIT and Boston Children Hospital research represents yet another promising step forward in this area
#Reseachers Create First Integrated Circularly Polarized Light detector on a Silicon chip What do you get when you combine some biomimicry, metamaterials and nanowires?
It turns out to be integrated the first circularly polarized light detector on a silicon chip. Its development could usher in a new generation of portable sensors that can use polarized light for applications ranging from drug screening to quantum computing.
Researchers at Vanderbilt University have used silver nanowires to fabricate a metamaterial that is capable of detecting polarized light in a way not unlike the way cuttlefish, bees,
or mantis shrimp do it. lthough it is largely invisible to human vision, the polarization state of light can provide a lot of valuable information,
said assistant professor Jason Valentine in a press release. owever, the traditional way of detecting it requires several optical elements that are quite bulky and difficult to miniaturize.
We have managed to get around this limitation by the use of etamaterials? materials engineered to have properties that are not found in nature. olarized light comes in basically two formsinear or circular.
In contrast to non-polarized light, in which the electric fields of the photons are oriented in random directions,
polarized light, whether linear or circular, features electric fields oriented in a single plane. With circularly polarized light,
the plane is continually rotating through 360 degrees.)One of the distinguishing capabilities of circularly polarized light (CPL) is that it can discern the difference between right-handed and left-handed versions of molecules property known as chirality.
or right handed determines their biological activity. For instance, there is the famous case of thalidomide, which in one chirality alleviates morning sickness in pregnant women and in the other causes birth defects.
Having a portable sensor capable of detecting a drug chirality could be a game changer. nexpensive CPL detectors could be integrated into the drug production process to provide real time sensing of drugs
said Vanderbilt University doctoral student Wei Li, in a press release. ortable detectors could be used to determine drug chirality in hospitals
and in the field. n research published in the journal Nature Communications, the researchers fabricated the portable CPL sensors by laying down nanowires in a zigzag pattern over a thin sheet of acrylic affixed to a thick silver plate.
This material is affixed to the bottom of a silicon wafer with the nanowire side up.
The nanowires create a sea of electrons that produces lasmondensity waves, the oscillations in the density of electrons that are generated
when photons hit a metal surface. These plasmon density waves absorb energy from the photons that pass through the silicon wafer.
The absorption of the energy produces otor energetic electrons, which generate a detectable electrical current.
The researchers found that they could make the zigzag pattern of nanowires with a right-or left-handed orientation.
When they arranged the nanowires in right-handed pattern, the surface absorbed right circularly polarized light
and reflected left circularly polarized light. When arranged in a left-handed pattern, the opposite effect occurred.
And when they arranged the nanowires to have both left-and right-handed patterns, the sensor could discern between left
and right circularly polarized light. The researchers concede that their current prototype is not efficient enough to be commercially viable.
However they have a few tricks up their sleeves that they believe will improve that efficiency in the next generation of their devices e
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