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By Admin (from 12/03/2011 @ 11:00:27, in en - Science and Society, read 1640 times)

Physicists are closer than ever to finding the source of the Universe's mysterious dark matter, following a better than expected year of research at the Compact Muon Solenoid (CMS) particle detector, part of the Large Hadron Collider (LHC) at CERN in Geneva.

The scientists have now carried out the first full run of experiments that smash protons together at almost the speed of light. When these sub-atomic particles collide at the heart of the CMS detector, the resultant energies and densities are similar to those that were present in the first instants of the Universe, immediately after the Big Bang some 13.7 billion years ago. The unique conditions created by these collisions can lead to the production of new particles that would have existed in those early instants and have since disappeared.

The researchers say they are well on their way to being able to either confirm or rule out one of the primary theories that could solve many of the outstanding questions of particle physics, known as Supersymmetry (SUSY). Many hope it could be a valid extension for the Standard Model of particle physics, which describes the interactions of known subatomic particles with astonishing precision but fails to incorporate general relativity, dark matter and dark energy.

Dark matter is an invisible substance that we cannot detect directly but whose presence is inferred from the rotation of galaxies. Physicists believe that it makes up about a quarter of the mass of the Universe whilst the ordinary and visible matter only makes up about 5% of the mass of the Universe. Its composition is a mystery, leading to intriguing possibilities of hitherto undiscovered physics.

Professor Geoff Hall from the Department of Physics at Imperial College London, who works on the CMS experiment, said: "We have made an important step forward in the hunt for dark matter, although no discovery has yet been made. These results have come faster than we expected because the LHC and CMS ran better last year than we dared hope and we are now very optimistic about the prospects of pinning down Supersymmetry in the next few years."

The energy released in proton-proton collisions in CMS manifests itself as particles that fly away in all directions. Most collisions produce known particles but, on rare occasions, new ones may be produced, including those predicted by SUSY – known as supersymmetric particles, or 'sparticles'. The lightest sparticle is a natural candidate for dark matter as it is stable and CMS would only 'see' these objects through an absence of their signal in the detector, leading to an imbalance of energy and momentum.

In order to search for sparticles, CMS looks for collisions that produce two or more high-energy 'jets' (bunches of particles travelling in approximately the same direction) and significant missing energy.

Dr Oliver Buchmueller, also from the Department of Physics at Imperial College London, but who is based at CERN, explained: "We need a good understanding of the ordinary collisions so that we can recognise the unusual ones when they happen. Such collisions are rare but can be produced by known physics. We examined some 3 trillion proton-proton collisions and found 13 'SUSY-like' ones, around the number that we expected. Although no evidence for sparticles was found, this measurement narrows down the area for the search for dark matter significantly."

The physicists are now looking forward to the 2011 run of the LHC and CMS, which is expected to bring in data that could confirm Supersymmetry as an explanation for dark matter.

The CMS experiment is one of two general purpose experiments designed to collect data from the LHC, along with ATLAS (A Toroidal LHC ApparatuS). Imperial’s High Energy Physics Group has played a major role in the design and construction of CMS and now many of the members are working on the mission to find new particles, including the elusive Higgs boson particle (if it exists), and solve some of the mysteries of nature, such as where mass comes from, why there is no anti-matter in our Universe and whether there are more than three spatial dimensions.

Source: PhysOrg - More Info at: CMS

 
By Admin (from 13/03/2011 @ 11:00:22, in en - Science and Society, read 2057 times)

An ant colony is the last place you'd expect to find a maths whiz, but University of Sydney researchers have shown that the humble ant is capable of solving difficult mathematical problems.

These findings, published in the Journal of Experimental Biology, deepen our understanding of how even simple animals can overcome complex and dynamic problems in nature, and will help computer scientists develop even better software to solve logistical problems and maximise efficiency in many human industries.

Using a novel technique, Chris Reid and Associate Professor Madeleine Beekman from the School of Biological Sciences, working with Professor David Sumpter of Uppsala University, Sweden, tested whether Argentine ants (Linepithema humile) could solve a dynamic optimisation problem by converting the classic Towers of Hanoi maths puzzle into a maze.

Finding the most efficient path through a busy network is a common challenge faced by delivery drivers, telephone routers and engineers. To solve these optimisation problems using software, computer scientists have often sought inspiration from ant colonies in nature - creating algorithms that simulate the behaviour of ants who find the most efficient routes from their nests to food sources by following each other's volatile pheromone trails. The most widely used of these ant-inspired algorithms is known as Ant Colony Optimisation (ACO).

"Although inspired by nature, these computer algorithms often do not represent the real world because they are static and designed to solve a single, unchanging problem," says lead author Chris Reid, a doctoral student from the Behaviour and Genetics of Social Insects Laboratory.

"But nature is full of unpredictability and one solution does not fit all. So we turned to ants to see how well their problem solving skills respond to change. Are they fixed to a single solution or can they adapt?"

The researchers tested the ants using the three-rod, three-disk version of the Towers of Hanoi problem - a toy puzzle that requires players to move disks between rods while obeying certain rules and using the fewest possible moves. But since ants cannot move disks, the researchers converted the puzzle into a maze where the shortest path corresponds to the solution with fewest moves in the toy puzzle. The ants at the entry point of the maze could chose between 32,768 possible paths to get to the food source on the other side, with only two of the paths being the shortest path and thus the optimal solution.

The ants were given one hour to solve the maze by creating a high traffic path between their nest and the food source, after which time the researchers blocked off paths and opened up new areas of the maze to test the ants' dynamic problem solving ability.

After an hour, the ants solved the Towers of Hanoi by finding the shortest path around the edge of the maze. But when that path was blocked off, the ants responded first by curving their original path around the obstacle and establishing a longer, suboptimal, route. But after a further hour, the ants had successfully resolved the maze by abandoning their suboptimal route and establishing a path that traversed through the centre of the maze on the new optimal route.

But not all the colonies' problem solving skills were equal: ants that were allowed to explore the maze without food for an hour prior to the test made fewer mistakes and were faster at resolving the maze compared to the ants that were naive. This result suggests that the "exploratory pheromone" laid down by ants searching a new territory is key in helping them adapt to changing conditions.

"Even simple mass-recruiting ants have much more complex and labile problem solving skills than we ever thought. Contrary to previous belief, the pheromone system of ants does not mean they get stuck in a particular path and can't adapt. Having at least two separate pheromones gives them much more flexibility and helps them to find good solutions in a changing environment. Discovering how ants are able to solve dynamic problems can provide new inspiration for optimisation algorithms, which in turn can lead to better problem-solving software and hence more efficiency for human industries."

Source: PhysOrg

 
By Admin (from 14/03/2011 @ 14:00:47, in en - Science and Society, read 1709 times)

Light-emitting diodes (LEDs) are an increasingly popular technology for use in energy-efficient lighting. Researchers from North Carolina State University have now developed a new technique that reduces defects in the gallium nitride (GaN) films used to create LEDs, making them more efficient.

LED lighting relies on GaN thin films to create the diode structure that produces light. The new technique reduces the number of defects in those films by two to three orders of magnitude. “This improves the quality of the material that emits light,” says Dr. Salah Bedair, a professor of electrical and computer engineering at NC State and co-author, with NC State materials science professor Nadia El-Masry, of a paper describing the research. “So, for a given input of electrical power, the output of light can be increased by a factor of two – which is very big.” This is particularly true for low electrical power input and for LEDs emitting in the ultraviolet range.

The researchers started with a GaN film that was two microns, or two millionths of a meter, thick and embedded half of that thickness with large voids – empty spaces that were one to two microns long and 0.25 microns in diameter. The researchers found that defects in the film were drawn to the voids and became trapped – leaving the portions of the film above the voids with far fewer defects.

Defects are slight dislocations in the crystalline structure of the GaN films. These dislocations run through the material until they reach the surface. By placing voids in the film, the researchers effectively placed a “surface” in the middle of the material, preventing the defects from traveling through the rest of the film.

The voids make an impressive difference.

“Without voids, the GaN films have approximately 10[to the 10th power] defects per square centimeter,” Bedair says. “With the voids, they have 10[to the 7th power] defects. This technique would add an extra step to the manufacturing process for LEDs,  but it would result in higher quality, more efficient LEDs.”

The paper, “Embedded voids approach for low defect density in epitaxial GaN films,” was published online Jan. 17 by Applied Physics Letters. The paper was co-authored by Bedair; Pavel Frajtag, a Ph.D. student at NC State; Dr. Nadia El-Masry, a professor of material science and engineering at NC State; and Dr. N. Nepal, a former post-doctoral researcher at NC State now working at the Naval Research Laboratory. The research was funded by the U.S. Army Research Office.

Source: NCSU News

 

A little disorder goes a long way, especially when it comes to harnessing the sun's energy. Scientists from the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) jumbled the atomic structure of the surface layer of titanium dioxide nanocrystals, creating a catalyst that is both long lasting and more efficient than all other materials in using the sun's energy to extract hydrogen from water.

Their photocatalyst, which accelerates light-driven chemical reactions, is the first to combine durability and record-breaking efficiency, making it a contender for use in several clean-energy technologies.

It could offer a pollution-free way to produce hydrogen for use as an energy carrier in fuel cells. Fuel cells have been eyed as an alternative to combustion engines in vehicles. Molecular hydrogen, however, exists naturally on Earth only in very low concentrations. It must be extracted from feedstocks such as natural gas or water, an energy-intensive process that is one of the barriers to the widespread implementation of the technology.

"We are trying to find better ways to generate hydrogen from water using sunshine," says Samuel Mao, a scientist in Berkeley Lab's Environmental Energy Technologies Division who led the research. "In this work, we introduced disorder in titanium dioxide nanocrystals, which greatly improves its light absorption ability and efficiency in producing hydrogen from water."

Mao is the corresponding author of a paper on this research that was published online Jan. 20, 2011 in Science Express with the title "Increasing Solar Absorption for Photocatalysis with Black, Hydrogenated Titanium Dioxide Nanocrystals." Co-authoring the paper with Mao are fellow Berkeley Lab researchers Xiaobo Chen, Lei Liu, and Peter Yu.

Mao and his research group started with nanocrystals of titanium dioxide, which is a semiconductor material that is used as a photocatalyst to accelerate chemical reactions, such as harnessing energy from the sun to supply electrons that split water into oxygen and hydrogen. Although durable, titanium dioxide isn't a very efficient photocatlayst. Scientists have worked to increase its efficiency by adding impurities and making other modifications.

The Berkeley Lab scientists tried a new approach. In addition to adding impurities, they engineered disorder into the ordinarily perfect atom-by-atom lattice structure of the surface layer of titanium dioxide nanocrystals. This disorder was introduced via hydrogenation.

The result is the first disorder-engineered nanocrystal. One transformation was obvious: the usually white titanium dioxide nanocrystals turned black, a sign that engineered disorder yielded infrared absorption.

The scientists also surmised disorder boosted the photocatalyst's performance. To find out if their hunch was correct, they immersed disorder-engineered nanocrystals in water and exposed them to simulated sunlight. They found that 24 percent of the sunlight absorbed by the photocatalyst was converted into hydrogen, a production rate that is about 100 times greater than the yields of most semiconductor photocatalysts.

In addition, their photocatalyst did not show any signs of degradation during a 22-day testing period, meaning it is potentially durable enough for real-world use.

Its landmark efficiency stems largely from the photocatalyst's ability to absorb infrared light, making it the first titanium dioxide photocatalyst to absorb light in this wavelength. It also absorbs visible and ultraviolet light. In contrast, most titanium dioxide photocatalysts only absorbs ultraviolet light, and those containing defects may absorb visible light. Ultraviolet light accounts for less than ten percent of solar energy.

"The more energy from the sun that can be absorbed by a photocatalyst, the more electrons can be supplied to a chemical reaction, which makes black titanium dioxide a very attractive material," says Mao, who is also an adjunct engineering professor in the University of California at Berkeley.

The team's intriguing experimental findings were further elucidated by theoretical physicists Peter Yu and Lei Liu, who explored how jumbling the latticework of atoms on the nanocrystal's surface via hydrogenation changes its electronic properties. Their calculations revealed that disorder, in the form of lattice defects and hydrogen, makes it possible for incoming photons to excite electrons, which then jump across a gap where no electron states can exist. Once across this gap, the electrons are free to energize the chemical reaction that splits water into hydrogen and oxygen.

"By introducing a specific kind of disorder, mid-gap electronic states are created accompanied by a reduced band gap," says Yu, who is also a professor in the University of California at Berkeley's Physics Department. "This makes it possible for the infrared part of the solar spectrum to be absorbed and contribute to the photocatalysis."

This research was supported by the Department of Energy's Office of Energy Efficiency and Renewable Energy. Transmission electron microscopy imaging used to study the nanocrystals at the atomic scale was performed at the National Center for Electron Microscopy, a national user facility located at Berkeley Lab.

Source: ScienceDaily

 
By Admin (from 21/03/2011 @ 11:00:12, in en - Science and Society, read 1584 times)

Solar cells are made from semiconductors whose ability to respond to light is determined by their band gaps (energy gaps). Different colors have different energies, and no single semiconductor has a band gap that can respond to sunlight's full range, from low-energy infrared through visible light to high-energy ultraviolet.

Although full-spectrum solar cells have been made, none yet have been suitable for manufacture at a consumer-friendly price. Now Wladek Walukiewicz, who leads the Solar Energy Materials Research Group in the Materials Sciences Division (MSD) at the U.S. Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab), and his colleagues have demonstrated a solar cell that not only responds to virtually the entire solar spectrum, it can also readily be made using one of the semiconductor industry's most common manufacturing techniques.

The new design promises highly efficient solar cells that are practical to produce. The results are reported in a recent issue of Physical Review Letters.

How to make a full-spectrum solar cell

"Since no one material is sensitive to all wavelengths, the underlying principle of a successful full-spectrum solar cell is to combine different semiconductors with different energy gaps," says Walukiewicz.

One way to combine different band gaps is to stack layers of different semiconductors and wire them in series. This is the principle of current high-efficiency solar cell technology that uses three different semiconductor alloys with different energy gaps. In 2002, Walukiewicz and Kin Man Yu of Berkeley Lab's MSD found that by adjusting the amounts of indium and gallium in the same alloy, indium gallium nitride, each different mixture in effect became a different kind of semiconductor that responded to different wavelengths. By stacking several of the crystalline layers, all closely matched but with different indium content, they made a photovoltaic device that was sensitive to the full solar spectrum.

However, says Walukiewicz, "Even when the different layers are well matched, these structures are still complex -- and so is the process of manufacturing them. Another way to make a full-spectrum cell is to make a single alloy with more than one band gap."

In 2004 Walukiewicz and Yu made an alloy of highly mismatched semiconductors based on a common alloy, zinc (plus manganese) and tellurium. By doping this alloy with oxygen, they added a third distinct energy band between the existing two -- thus creating three different band gaps that spanned the solar spectrum. Unfortunately, says Walukiewicz, "to manufacture this alloy is complex and time-consuming, and these solar cells are also expensive to produce in quantity."

The new solar cell material from Walukiewicz and Yu and their colleagues in Berkeley Lab's MSD and RoseStreet Labs Energy, working with Sumika Electronics Materials in Phoenix, Arizona, is another multiband semiconductor made from a highly mismatched alloy. In this case the alloy is gallium arsenide nitride, similar in composition to one of the most familiar semiconductors, gallium arsenide. By replacing some of the arsenic atoms with nitrogen, a third, intermediate energy band is created. The good news is that the alloy can be made by metalorganic chemical vapor deposition (MOCVD), one of the most common methods of fabricating compound semiconductors.

How band gaps work

Band gaps arise because semiconductors are insulators at a temperature of absolute zero but inch closer to conductivity as they warm up. To conduct electricity, some of the electrons normally bound to atoms (those in the valence band) must gain enough energy to flow freely -- that is, move into the conduction band. The band gap is the energy needed to do this.

When an electron moves into the conduction band it leaves behind a "hole" in the valence band, which also carries charge, just as the electrons in the conduction band; holes are positive instead of negative.

A large band gap means high energy, and thus a wide-band-gap material responds only to the more energetic segments of the solar spectrum, such as ultraviolet light. By introducing a third band, intermediate between the valence band and the conduction band, the same basic semiconductor can respond to lower and middle-energy wavelengths as well.

This is because in a multiband semiconductor, there is a narrow band gap that responds to low energies between the valence band and the intermediate band. Between the intermediate band and the conduction band is another relatively narrow band gap, one that responds to intermediate energies. And finally, the original wide band gap is still there to take care of high energies.

"The major issue in creating a full-spectrum solar cell is finding the right material," says Kin Man Yu. "The challenge is to balance the proper composition with the proper doping."

In solar cells made of some highly mismatched alloys, a third band of electronic states can be created inside the band gap of the host material by replacing atoms of one component with a small amount of oxygen or nitrogen. In so -- called II-VI semiconductors (which combine elements from these two groups of Mendeleev's original periodic table), replacing some group VI atoms with oxygen produces an intermediate band whose width and location can be controlled by varying the amount of oxygen. Walukiewicz and Yu's original multiband solar cell was a II-VI compound that replaced group VI tellurium atoms with oxygen atoms. Their current solar cell material is a III-V alloy. The intermediate third band is made by replacing some of the group V component's atoms -- arsenic, in this case -- with nitrogen atoms.

Finding the right combination of alloys, and determining the right doping levels to put an intermediate band right where it's needed, is mostly based on theory, using the band anticrossing model developed at Berkeley Lab over the past 10 years.

"We knew that two-percent nitrogen ought to do the job," says Yu. "We knew where the intermediate band ought to be and what to expect. The challenge was designing the actual device."

Passing the test

Using their new multiband material as the core of a test cell, the researchers illuminated it with the full spectrum of sunlight to measure how much current was produced by different colors of light. The key to making a multiband cell work is to make sure the intermediate band is isolated from the contacts where current is collected.

"The intermediate band must absorb light, but it acts only as a stepping stone and must not be allowed to conduct charge, or else it basically shorts out the device," Walukiewicz explains.

The test device had negatively doped semiconductor contacts on the substrate to collect electrons from the conduction band, and positively doped semiconductor contacts on the surface to collect holes from the valence band. Current from the intermediate band was blocked by additional layers on top and bottom.

For comparison purposes, the researchers built a cell that was almost identical but not blocked at the bottom, allowing current to flow directly from the intermediate band to the substrate.

The results of the test showed that light penetrating the blocked device efficiently yielded current from all three energy bands -- valence to intermediate, intermediate to conduction, and valence to conduction -- and responded strongly to all parts of the spectrum, from infrared with an energy of about 1.1 electron volts (1.1 eV), to over 3.2 eV, well into the ultraviolet.

By comparison, the unblocked device responded well only in the near infrared, declining sharply in the visible part of the spectrum and missing the highest-energy sunlight. Because it was unblocked, the intermediate band had essentially usurped the conduction band, intercepting low-energy electrons from the valence band and shuttling them directly to the contact layer.

Further support for the success of the multiband device and its method of operation came from tests "in reverse" -- operating the device as a light emitting diode (LED). At low voltage, the device emitted four peaks in the infrared and visible light regions of the spectrum. Primarily intended as a solar cell material, this performance as an LED may suggest additional possibilities for gallium arsenide nitride, since it is a dilute nitride very similar to the dilute nitride, indium gallium arsenide nitride, used in commercial "vertical cavity surface-emitting lasers" (VCSELs), which have found wide use because of their many advantages over other semiconductor lasers.

With the new, multiband photovoltaic device based on gallium arsenide nitride, the research team has demonstrated a simple solar cell that responds to virtually the entire solar spectrum -- and can readily be made using one of the semiconductor industry's most common manufacturing techniques. The results promise highly efficient solar cells that are practical to produce.

Source: ScienceDaily

 

Any city will find that a logistics system that effectively supports flow of goods from one point to another is a crucial point in keeping things running. Fleets of vehicles currently travel around the country delivering food, clothing and other stock, but at the cost of heavy emissions. While there are plans to increase the use of rail freight, inner-city deliveries are still plagued with carbon heavy emissions. So what’s the solution? Enter the eStar Electric Vehicle, a green delivery vehicle that boasts an impressive 4,000 pound payload and can travel 100 miles on a single charge.

Designed by green vehicles specialist Navistar, the eStar aims to press companies to re-evaluate how they outfit their fleets. Navistar says of their ‘peppy’ little vehicle that it is “designed from the ground up to be electric, eStar is more efficient and effective than typical electric conversions.”

It is also easy to charge as the eStar offers a simple 220 volt split phase electrical charging process that’s quick and efficient. This means that the eStar can recharge overnight in approximately 8 hours and be ready for work in the morning.

Spec-wise the eStar runs on a 80kWhr Li-ion cassette battery providing 102 horsepower and 70kw of power. With a top speed of 50 mph and zero emissions, the eStar is ideal for inner-city work. The vehicle’s size also gives it room to move. Its 36-foot turning diameter helps in navigating small spaces, while the open view from the cab gives the driver a clear 180 degree view.

If you run a business in a big city, be it flower deliveries or catering, and are looking to green up your fleet, this could provide the answer.

Beyond the transport of passengers, to ensure that we are reducing our carbon footprint, we need to consider clean automotive in all applications, even in the local delivery of goods.

Source: Inhabitat

 
By Admin (from 25/03/2011 @ 14:00:10, in en - Science and Society, read 3208 times)

Excessive packaging is responsible for a lot of waste.

Because of this we were really inspired by this flat cardboard sheet that is capable of conforming to the shape of any object, saving a bundle on wasteful filler. Designed by Patrick Sung, the packaging design concept features triangulated perforations that allow it to bend around odd forms. This could also save on fuel for shipping, since all of that wasted box filler is eliminated.

We could see how the concept would not be the most practical for all applications, but it could be really great for mailing a surprise gift to a friend! Soft items like clothing or shoes, or even products that are rigid, like a funky reusable water bottle, could be perfect for this packaging. Not to mention that the perforated lines give the package an interesting graphic pattern style. There is something to be said about the efficiency of boxes that stack, which is why it is great that the sheet can also be folded into standard 6-sided boxes.

Sung has branded his concept the UPACKS (Universal Packaging System).

Source: Inhabitat

 
By Admin (from 27/03/2011 @ 08:00:53, in en - Science and Society, read 2557 times)

There are very few urban design solutions that address housing the tide of displaced people that could arise as oceans swell under global warming. Certainly few are as spectacular as this one.

 

 

 

 

 

The Lilypad, by Vincent Callebaut, is a concept for a completely self-sufficient floating city intended to provide shelter for future climate change refugees. The intent of the concept itself is laudable, but it is Callebaut’s phenomenal design that has captured our imagination.

Biomimicry was clearly the inspiration behind the design. The Lilypad, which was designed to look like a waterlily, is intended to be a zero emission city afloat in the ocean. Through a number of technologies (solar, wind, tidal, biomass), it is envisioned that the project would be able to not only produce it’s own energy, but be able to process CO2 in the atmosphere and absorb it into its titanium dioxide skin.

Each of these floating cities are designed to hold approximately around 50,000 people. A mixed terrain man-made landscape, provided by an artificial lagoon and three ridges, create a diverse environment for the inhabitants. Each Lilypad is intended to be either near a coast, or floating around in the ocean, traveling from the equator to the northern seas, according to where the gulf stream takes it.

The project isn’t even close to happening anytime soon, but there is value in future forward designs like the Lilypad. They inspire creative solutions, which at some point, may actually provide a real solutions to various problems.

The oceans take up roughly 70% of the earth's surface. That being said, the land left to live on is scattered through mountains, desserts and ice caps. This has prevented humans from settling at many places. The oceans however, are flat and full of life, space & energy. These factors could provide us with all the necessities for a future life at at sea...

Source: inhabitat

 
By Admin (from 28/03/2011 @ 08:00:27, in en - Science and Society, read 1218 times)

Many trees disperse their seeds by releasing "helicopters," those single-winged seeds that are also called "samaras." As these seeds fall to the ground, their wing causes them to swirl and spin in a process called autorotation, similar to man-made helicopters. In a new study, researchers have designed and built a mechanical samara whose dynamics are very similar to those of nature’s samaras. After testing the mechanical samara, the researchers then built a variety of remote-controlled robotic samaras with onboard power sources.
The researchers, Evan Ulrich, Darryll Pines, and Sean Humbert from the University of Maryland, have published their study on the robotic samaras in a recent issue of Bioinspiration & Biomimetics. The idea for building a flying robotic device based on samaras originated several years ago, after researchers attempted to scale down full-size helicopters.

“Full-scale helicopters have a high aerodynamic efficiency,” Ulrich, a PhD candidate, told PhysOrg.com. “But the aerodynamic efficiency is disproportionate, so a scaled-down helicopter has stability issues and is unfeasible. Dr. Pines, my advisor, realized that the simplest system in nature that achieves vertical flight and can autorotate like a helicopter is the samara, which is a naturally stable system.”

After further investigating the samara in order to better understand its flight dynamics, the researchers found that the winged seed is also one of nature’s most efficient fliers. The samara is a monocopter, meaning it has a single wing. For this reason, the samara has no stationary frame of reference, unlike a two-winged helicopter, and appears to fall in a complex way. However, through free-fall testing, the researchers could quantitatively measure the samara’s flight dynamics and use this information to control the samara’s autorotation and flight path.

After designing and building a mechanical samara, the researchers measured its flight dynamics in free-fall by dropping it from a height of 12 meters. Then the scientists used this data to develop three different designs of powered robotic samaras, ranging in size from 7.5 cm to 0.5 m. In flight tests, they demonstrated that the carbon fiber-based robotic samaras could be remotely steered to a desired location by altering the wing pitch, which changes the radius at which the vehicles turn. The robotic samaras could also hover, climb, and translate.

The researchers noted that the concept of a single-wing rotating aircraft is not new, with the first such vehicle being flown in 1952 by Charles McCutchen near Lake Placid, New York. Since then, several other single-winged rotating aircraft have been developed, but none of these designs has used autorotation or been based on the samara.
The samara-inspired autorotation process has several advantages compared to other small-scale aircraft that perform vertical take-off and landing. For instance, the robotic samaras are extremely damage-tolerant. If they lose power while flying, they can autorotate down and land without sustaining any damage due to their flexible structure that deflects upon impact. The robotic samaras are also passively stable, inexpensive, mechanically simple, and have a high payload capacity. Flight time is around 30 minutes, but depends on the battery size.

In the future, Ulrich plans to start a company to license and develop the technology for commercialization. In addition to developing the robotic samara into a toy, he said that the device could also have applications in satellite communications and 3D mapping.

“We want to take advantage of the autorotation mode since it doesn’t require power for flight,” he said. “If we can find a vertical column of air, it can stay aloft indefinitely. One possibility is using it as an autorotating communications platform to carry small components for satellites, without the requirement of a huge launch cost.”
In addition, since the device is continuously spinning, an onboard camera could be used to take 360° images and build a 3D map. The robotic samara spins about 15 times per second and can navigate through small areas and avoid obstacles, giving it advantages over larger vehicles such as helicopters and airplanes.

Source: PhysOrg

 
By Admin (from 29/03/2011 @ 11:00:50, in en - Science and Society, read 1659 times)

The Double Chooz collaboration recently completed its neutrino detector which will see anti-neutrinos coming from the Chooz nuclear power plant in the French Ardennes. The experiment is now ready to start collecting data in order to measure fundamental neutrino properties with important consequences for particle and astro-particle physics.

Neutrinos are electrically neutral elementary particles, three of a kind plus their antiparticles. Though already postulated in 1930 their first experimental observation was made in 1956. Because of their weak interaction with other particles, matter is almost completely transparent to neutrinos and large sensitive detectors are needed to capture them.

Neutrino oscillations were a major discovery in the late 1990s with the corresponding experiments being included in the 2002 Nobel Prize. Oscillations describe in-flight transformations of different neutrino species into each other and the observation of this effect implies that neutrinos do have mass. The oscillations depend on three mixing parameters, of which two are large and have already been measured. The third one is called theta13 and is known to be smaller with an upper limit coming from a previous experiment at Chooz. The new Double Chooz detector is the first of a new generation of reactor neutrino experiments with the aim of measuring this fundamental parameter in neutrino physics which is a key area of particle physics research. The results will also have important consequences for the feasibility of future neutrino facilities which will aim for even more precise measurements.

Double Chooz consists of two identical detectors. The first one, at a distance of about 1km from the reactor cores, has now been filled and started to collect data. The number of neutrinos measured compared to the expected flux from the reactors will allow considerably improvement in the sensitivity for theta13 already in 2011. The second detector, located at a distance of 400 metres, will start operating in 2012. At this distance no significant transformation into another neutrino species is expected. By comparing the results from both detectors, theta13 can be determined with even higher precision.

Both detectors use an organic liquid scintillator, which was developed specifically for this experiment. The neutrino target in the core of the detector consists of 10 cubic metres of Gadolinium doped scintillator which can be used to tag neutrons from inverse beta decays which are induced by anti-neutrinos emitted by the reactors. The target is surrounded by three layers of other liquids in order to protect against other particles and to dampen environmental radioactivity. These liquids are contained in very thin vessels so as to minimize inactive volumes inside the detector. The target is observed by 390 immersed photomultipliers which convert the interactions into electrical signals. These signals are processed in a data acquisition system which can collect data over the next five years. The new detectors will ensure that neutrino physics will stay one the most fruitful areas of particle physics, as it has been for the past 50 years.

An essential contribution to the project was the development of the gadolinium-doped liquid scintillator by the researchers at the Max Planck Institute for Nuclear Physics in Heidelberg. Their task was to find, test, produce and purify a gadolinium compound which is solvable in an organic liquid and chemically stable for many years. In collaboration with their colleagues from Japan they checked the photomultipliers in a specially built test-bed. These central contributions will also play a crucial role for the interpretation and data analysis. Universities and research institutes from Brazil, England, France, Germany, Japan, Russia, Spain and USA comprise the Double Chooz collaboration.

Source: PhysOrg

 
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Titolo
en - Global Observatory (605)
en - Science and Society (594)
en - Video Alert (346)
it - Osservatorio Globale (503)
it - Scienze e Societa (555)
it - Video Alerta (132)
ro - Observator Global (399)
ro - Stiinta si Societate (467)
ro - TV Network (149)
z - Games Giochi Jocuri (68)

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Ultimi commenti - Last comments - Ultimele comentarii:
Hi, it's Nathan!Pretty much everyone is using voice search with their Siri/Google/Alexa to ask for services and products now, and next year, it'll be EVERYONE of your customers. Imagine what you are ...
15/01/2019 @ 17:58:25
By Nathan
Now Colorado is one love, I'm already packing suitcases;)
14/01/2018 @ 16:07:36
By Napasechnik
Nice read, I just passed this onto a friend who was doing some research on that. And he just bought me lunch since I found it for him smile So let me rephrase that Thank you for lunch! Whenever you ha...
21/11/2016 @ 09:41:39
By Anonimo


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27/07/2021 @ 11:33:49
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