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Category: materials

A full-scale demonstrator of the thrust chamber for an upper-stage rocket engine incorporating the newest propulsion technologies is being prepared for its first hot firing.

The Expander-cycle Technology Integrated Demonstrator, or ETID, has arrived at the DLR German Aerospace Center test facility in Lampoldshausen for tests. It will help to prove new technologies, materials and manufacturing techniques that offer higher performance at lower cost for Europe’s future launchers.

ETID is a precursor of the next generation of 10-tonne rocket engines. Some of the technologies could also be used on upgrades to the existing Vinci, which powers the upper stage of Ariane 6.

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Piezoelectric materials, which generate an electric current when compressed or stretched, are familiar and widely used: think of lighters that spark when you press a switch, but also microphones, sensors, motors and all kinds of other devices. Now a group of physicists has found a material with a similar property, but for magnetism. This “piezomagnetic” material changes its magnetic properties when put under mechanical strain.

“Piezomagnetic materials are rarely found in nature, as far as I’m aware,” said Nicholas Curro, professor of physics at UC Davis and senior author of a paper on the discovery published March 13 in the journal Nature Communications.

Curro and colleagues were studying a barium-iron-arsenic compound, BaFe2As2, that can act as a superconductor at temperatures of about 25 Kelvin when doped with small amounts of other elements. This type of iron-based superconductor is interesting because although it has to be kept pretty cold to work, it could be stretched into wires or cables.

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Virtual assistants and chatbots don’t have a lot of common sense. It’s because these types of machine learning rely on specific situations they have encountered before, rather than using broader knowledge to answer a question. However, researchers at the Allen Institute for AI (Ai2) have devised a new test, the Arc Reasoning Challenge (ARC) that can test an artificial intelligence on its understanding of the way our world operates.

Humans use common sense to fill in the gaps of any question they are posed, delivering answers within an understood but non-explicit context. Peter Clark, the lead researcher on ARC, explained in a statement, “Machines do not have this common sense, and thus only see what is explicitly written, and miss the many implications and assumptions that underlie a piece of text.”

The test asks basic multiple-choice questions that draw from general knowledge. For example, one ARC question is: “Which item below is not made from a material grown in nature?” The possible answers are a cotton shirt, a wooden chair, a plastic spoon and a grass basket.

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As hemp makes a comeback in the U.S. after a decades-long ban on its cultivation, scientists are reporting that fibers from the plant can pack as much energy and power as graphene, long-touted as the model material for supercapacitors. They’re presenting their research, which a Canadian start-up company is working on scaling up, at the 248th National Meeting & Exposition of the American Chemical Society (ACS).

David Mitlin, Ph.D., explains that are energy storage devices that have huge potential to transform the way future electronics are powered. Unlike today’s rechargeable batteries, which sip up energy over several hours, supercapacitors can charge and discharge within seconds. But they normally can’t store nearly as much energy as batteries, an important property known as energy density. One approach researchers are taking to boost supercapacitors’ energy density is to design better electrodes. Mitlin’s team has figured out how to make them from certain fibers—and they can hold as much energy as the current top contender: graphene.

“Our device’s electrochemical performance is on par with or better than graphene-based devices,” Mitlin says. “The key advantage is that our electrodes are made from biowaste using a simple process, and therefore, are much cheaper than graphene.”

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A new study has revealed that the optical waves or light waves can be turned upside down when they are allowed to propagate through specifically structured surfaces. Normally what happens is that the optical waves emerging out from a point source propagate circularly. That means the optical waves traveling away from a point source characteristically display circular, or convex, wavefronts.

The scientists compared these circular wavefronts to the waves seen on the water surface when a stone is dropped into the water. But the latest study revealed that these circularly propagating light waves’ wavefronts can be turned upside down with the help of a special surface. They developed a new material having a hyperbolic metasurface and successfully inverted the optical waves.

The study was led by Peining Li, an EU Marie Sklodowska-Curie fellow at nanoGUNE. According to him, the reason behind this circular propagation of optical waves is because of the fact that the medium through which light waves propagate is isotropic and homogenous. If the waves are isotropic in nature then their propagation is uniform in all direction and being homogenous means they carry the same characteristics throughout the propagation. But these optical waves can be inverted using specifically structured surfaces like the hyperbolic metasurfaces.

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Using a type of graphene called Graphair, scientists from Australia have created a water filter that can make highly polluted seawater drinkable after just one pass.

The technology could be used to cheaply provide safe drinking water to regions of the world without access to it.

“Almost a third of the world’s population, some 2.1 billion people, don’t have clean and safe drinking water,” said lead author Dong Han Seo.

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(Left) Superatomic structure and (right) exfoliated 15-nm-thick flakes of the material Re6Se8Cl2. Credit: Zhong et al. ©2018 American Chemical Society Atoms are the basic building blocks of all matter—at least, that is the conventional picture. In a new study, researchers have fabricated the first superatomic 2-D semiconductor, a material whose basic units aren’t atoms but superatoms—atomic clusters that exhibit some of the properties of one or more individual atoms. The researchers expect that the new material is just the first member of what will become a new family of 2-D semiconductors…

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