Technology

Fog can play a key role in cloaking military invasions and retreats and the actions of intruders. That’s why physical security experts seek to overcome fog, but it’s difficult to field test security cameras, sensors or other equipment in fog that is often either too thick or too ephemeral.
Until now, collecting field test data in foggy environments was time-consuming and costly. “Fog is difficult to work with because it rarely shows up when needed, it never seems to stay around long enough once you’re ready to test and its density can vary during testing,” said Rich Contreras, a systems engineer at Sandia National Laboratories.
That’s why Contreras and others started thinking about developing a controlled-fog environment for sensor testing. The sunny, high desert of New Mexico may seem an unlikely place to make fog, but Sandia has developed a fog chamber—one of the world’s largest—that meets the needs of the military, other government agencies and industry. The chamber is in a tunnel owned by the Air Force Research Laboratory.
“The ultimate goal of this whole endeavor is to defeat fog,” Contreras said. “From physical security and force protection aspects, as scientists and engineers who care about national security, we want to be able to make it so that a security force person at a site has the ability to maintain uninterrupted situational awareness.”
Researchers say the chamber will help develop and validate cameras’ and sensors’ abilities to penetrate fog, knowledge that could lead to improved surveillance at sites. The chamber also could be used to answer fundamental optics questions, which in time could lead to improved security camera lenses and medical imaging equipment, safer aircraft landings and better vision for drivers in fog.
“People need to see through fog,” said optical scientist Gabe Birch. “So much of the U.S. population is on the coastlines in places where fog exists. If you could discover an inexpensive technique to see better through it, there are a lot of people in industry who would be interested in that.”

Cloud microphysics used to characterize fog, prolong testing

This is not your Halloween party fog machine. Sandia’s fog chamber is 180 feet long, 10 feet tall and 11 feet wide. The chamber is enclosed by air curtains and rubber baffles to entrap the fog, approximating real-world conditions. Tunnel walls are painted with a special black paint to reduce reflection and improve data quality, Contreras said

Walk a few steps down the hallway when the chamber’s fog is at full strength and a sense of disorientation washes over an observer as the walls, ceiling and entranceway disappear and people only a few feet away fade first into dark, obscure silhouettes and then become invisible.
Sandia researchers use cloud microphysics to generate fog for video analytics, environmental testing and new sensor development. Currently, the chamber’s fog resembles that found in coastal regions, but output can be customized to produce fog physically similar to that found in any location, said Crystal Glen, an aerosol scientist. Researchers eventually hope to add smoke and dust to the chamber’s repertoire.
In the atmosphere, fog forms from a seed particle, such as pollen or sea salt, surrounded by layers of water. Seed particles differ based on the fog’s location. Sandia currently uses sodium chloride, or sea salt, as its seed particle to mimic the composition and particle size of coastal fog. By consulting journals or traveling to a region, researchers can measure the droplet size distribution and chemical composition of different fogs worldwide and then alter the seed particles to customize the fog.
The longer the fog’s seed particles hold onto the water layer, the longer they are visible for testing. The length of the test depends on the relative humidity in the chamber.
Glen mixes a solution of sodium chloride and water that produces the desired core particle seed diameter. The solution is sprayed into the chamber where the relative humidity is above 95 percent. The initial sprayed droplets are roughly 2.3 times their dry diameter.

The deliquescence point, or the amount of relative humidity required for a particle to take on water, happens at 72 percent relative humidity for coastal fog, primarily composed of sodium chloride. The amount of water clinging to the seed particle grows exponentially from there. This process happens naturally in the atmosphere and leads to fog and cloud formation, Glen said.
To speed up Mother Nature, Glen checks the rate at which a particle will gain or lose water in relation to the chamber’s relative humidity, termed the hysteresis curve for water interactions with sodium chloride. This information allows the team to target a specific relative humidity and obtain a desirable size for the wet particles, so the droplet size distribution is close to what is found in natural fog, she said. While the fog generated in the chamber is not identical to fog formed in nature, it is physically representative and extremely useful for research involving optical transmission and visibility.
Typically, gravity causes the fog to settle before the decrease in relative humidity takes effect. The fog density can remain constant for up to 30 minutes, allowing a test to last 10-20 minutes. Adding a 30-second blast of fog particles can prolong the testing, Glen said, adding that the fog’s density can be controlled by the amount sprayed into the chamber or the particle size.

Optics experts see potential of controlled fog

The layer of water around the fog seed particles either absorbs the photons, the elementary particles and waves that make up light, or causes them to change direction in random ways, so that by the time they reach the cameras being tested, the wavelengths being picked up create a fuzzy image, Birch said.

Optics researchers refer to fog and seeing through bodily tissue in medical imaging as “scattering environments.” Sandia optical engineer David Scrymgeour likens the photons’ movements in these environments to walking through a sunny, full parking lot and seeing glints of light bounce in every direction off windshields.

In fog, it’s the scattering of the photons that causes the car headlights or a pedestrian’s flashlight beam to illuminate an entire scene, making vision even more difficult, Scrymgeour explained.

In physical security, “the cameras are very sensitive to the sizes of fog particles and how the photons scatter. That’s why it’s so important to know the sizes of particles that we have in the environment, which is something that we in the optical field have not really had before,” Birch said. “It enables a lot of very interesting testing because you can finally characterize your system’s performance by knowing the scattering that’s happening in the environment.”

Fog chamber tests could lead to security camera improvements

For the military or any agency seeking to physically secure a site, not knowing the exact ranges that cameras can penetrate fog in a particular environment makes it difficult to choose the correct cameras and sensors and their placements, Contreras said.

Birch explained: “It’s very difficult to quantitatively compare all those modalities together with the same fog and in the same conditions because you go outside and five minutes later it could be very different.”

Once the chamber’s fog density is set, cameras or sensors mounted at one end of the tunnel are monitored to see how well they detect humans or custom targets, Contreras said.

Different types of lighting representing specific sites could be installed in the chamber to see the combined effect of fog and lighting or the desired time of day, he said.

Examples of tests include showing raw data from various cameras, characterizing how different wavelengths and polarization states are influenced by fog, comparing different optical systems in a controlled foggy environment and resolution testing to see how the optical properties and resolution degrade in a variety of foggy environments, Birch said. Polarization states describe the way electromagnetic waves oscillate as they propagate in space.

Fog chamber could provide answers for optics research

The fog chamber also could be used to answer fundamental scientific questions.

“When you look at the huge gap from the visible spectrum all the way up to the far infrared, no one can say we absolutely understand how the polarization states at all these different wavelengths behave as they go through a foggy atmosphere,” Birch said.

Recent research at Sandia has suggested that the polarization of photons could be exploited to see better through fog or other scattering environments, Scrymgeour said.

Researchers have ideas about how to use optics—for example, a filter on a camera lens—to exploit polarization, he added, but they need to be tested in a real-world environment, like the fog chamber.

Such testing could inform not only physical security camera design to better handle fog, but also medical imaging, he said, “The physics in scattering events are the same.”

References:http://phys.org/

Now even computers are going to be critical of how we look: algorithms are getting into style. New software judges outfits from a photograph and offers tips to make them look even more chic.

“Not everyone has access to an expert,” says Raquel Urtasun, a computer scientist at the University of Toronto, Canada, who developed the software with colleagues in Spain. “You can imagine something like this being used [to style photos for] dating sites and Facebook profiles.”

Fashion is as tough for machines to master Movie Cameraas it is for us, if not more so, largely because it is so subjective. What’s popular now may become passé in a few months, and what works well in a particular culture or setting could be wildly inappropriate in another: think about clothes for date night and clothes for the office. And before a computer works any of this out, it has to be able to correctly identify each item of clothing being worn.

To teach the software about fashion, Urtasun’s team showed it thousands of pictures from Chictopia, a popular style website. The more positive votes left by other users, the more “fashionable” the software perceived the look to be.

It also noted other information about the photo, such as the user’s geographic location, the date they had posted it, the background of the picture, and written descriptions of the clothing.

The resulting software uses this information to categorise outfits and make suggestions based on what was successful for others in similar situations – for example, to add black boots or try something in pastel. The team plans to hone the results further by showing it a more diverse array of photos from other sources.

Urtasun presented the work at the Computer Vision and Pattern Recognition conference in Boston, Massachusetts, earlier this month. Her team plans to improve the software so that it can automate the work of a human stylist.

Alexandra Greenawalt, a personal stylist in New York City, is understandably sceptical about computers muscling in on her patch. Looking good is about more than the latest trends, she says.

When dressing clients, she considers a wide range of factors, including their age, occupation and body shape. An effective algorithm would need to take all that into account, too.

Still, she is curious to watch the technology develop. “What will be interesting to see is if it can predict fashion before it happens or just based on likes in the past,” she says. “I would imagine the teens and 20-year-olds who are very much wanting to be in fashion would find it valuable.”

References:http://www.newscientist.com/

Stretchy batteries inspired by origami could power smartwatches and other wearable electronics, researchers say.

Increasingly, scientists worldwide are developing flexible electronics, such as video displays and solar panels, that could one day make their way into clothing and even human bodies. But one limitation of these devices is the scarcity of equally flexible batteries to power them or store energy they generate.

Although prior research has created bendable batteries, it has proven more challenging to developing ones that are stretchy versions has proven more challenging, researchers said. Now, inventors have created lithium-ion batteries that can stretch to more than 150 percent of their original size, while remaining capable of powering devices. [Top 10 Inventions that Changed the World]

Hanqing Jiang, an associate professor of mechanical and aerospace engineering at Arizona State University in Tempe, came up with the new device after “talking with an origami artist who showed me some famous origami patterns,” he said. One of these patterns, known as the Miura-ori fold, is currently used to fold large maps into small rectangles, and was originally invented to help pack solar panels efficiently on spacecraft.

One problem with using principles of origami to create electronics is that folding often produces uneven surfaces. This can make it difficult to integrate these devices with other electronics, the researchers said.

Instead, Jiang and his colleagues used a variation of origami known as kirigami to create their stretchable batteries. Whereas conventional origami uses only folding to create structures, kirigami uses both folding and cutting. The technique results in structures whose surfaces can stay even after stretching.

“We found a new approach to make stretchable structures using conventional manufacturing approaches,” Jiang said.

The batteries were created using slurries of graphite and lithium cobalt dioxide, which together can store and release electricity. These slurries were coated onto sheets of aluminum foil, and kirigami techniques were then used to fold and cut the sheets into stretchy serpentine shapes.

In experiments, the new batteries could power a Samsung Gear 2 smartwatch even when stretched, the researchers said. The batteries could easily be sewn into a stretchy wristband, which suggests they could be used in flexible wearable devices.

Another research team recently developed a battery that could stretch to 300 percent its original size. In this device, the energy-storing materials were sandwiched between thin sheets of silicon rubber. Jiang said his new battery has an advantage over this previous battery because his is compatible with commercially available manufacturing technologies.

The researchers are now working on creating microscopic origami patterns to combine stretchable batteries with microelectronics. Jiang and his colleagues detailed their findings online June 11 in the journal Scientific Reports.

References:http://www.livescience.com/

Graphene, a form of carbon famous for being stronger than steel and more conductive than copper, can add another wonder to the list: making light.

Researchers have developed a light-emitting graphene transistor that works in the same way as the filament in a light bulb.

“We’ve created what is essentially the world’s thinnest light bulb,” study co-author James Hone, a mechanical engineer at Columbia University in New York, said in a Scientists have long wanted to create a teensy “light bulb” to place on a chip, enabling what is called photonic circuits, which run on light rather than electric current. The problem has been one of size and temperature — incandescent filaments must get extremely hot before they can produce visible light. This new graphene device, however, is so efficient and tiny, the resulting technology could offer new ways to make displays or study high-temperature phenomena at small scales, the researchers said. [8 Chemical Elements You’ve Never Heard Of]

Making light

When electric current is passed through an incandescent light bulb’s filament — usually made of tungsten — the filament heats up and glows. Electrons moving through the material knock against electrons in the filament’s atoms, giving them energy. Those electrons return to their former energy levels and emit photons (light) in the process. Crank up the current and voltage enough and the filament in the light bulb hits temperatures of about 5,400 degrees Fahrenheit (3,000 degrees Celsius) for an incandescent. This is one reason light bulbs either have no air in them or are filled with an inert gas like argon: At those temperatures tungsten would react with the oxygen in air and simply burn.

In the new study, the scientists used strips of graphene a few microns across and from 6.5 to 14 microns in length, each spanning a trench of silicon like a bridge. (A micron is one-millionth of a meter, where a hair is about 90 microns thick.) An electrode was attached to the ends of each graphene strip. Just like tungsten, run a current through graphene and the material will light up. But there is an added twist, as graphene conducts heat less efficiently as temperature increases, which means the heat stays in a spot in the center, rather than being relatively evenly distributed as in a tungsten filament.

Myung-Ho Bae, one of the study’s authors, told Live Science trapping the heat in one region makes the lighting more efficient. “The temperature of hot electrons at the center of the graphene is about 3,000 K [4,940 F], while the graphene lattice temperature is still about 2,000 K [3,140 F],” he said. “It results in a hotspot at the center and the light emission region is focused at the center of the graphene, which also makes for better efficiency.” It’s also the reason the electrodes at either end of the graphene don’t melt.

As for why this is the first time light has been made from graphene, study co-leader Yun Daniel Park, a professor of physics at Seoul National University, noted that graphene is usually embedded in or in contact with a substrate.

“Physically suspending graphene essentially eliminates pathways in which heat can escape,” Park said. “If the graphene is on a substrate, much of the heat will be dissipated to the substrate. Before us, other groups had only reported inefficient radiation emission in the infrared from graphene.”

The light emitted from the graphene also reflected off the silicon that each piece was suspended in front of. The reflected light interferes with the emitted light, producing a pattern of emission with peaks at different wavelengths. That opened up another possibility: tuning the light by varying the distance to the silicon.

The principle of the graphene is simple, Park said, but it took a long time to discover.

“It took us nearly five years to figure out the exact mechanism but everything (all the physics) fit. And, the project has turned out to be some kind of a Columbus’ Egg,” he said, referring to a legend in which Christopher Columbus challenged a group of men to make an egg stand on its end; they all failed and Columbus solved the problem by just cracking the shell at one end so that it had a flat bottom.

References:http://www.livescience.com/