Researchers at the Institute of Acoustics (IOA) of the Chinese Academy of Sciences have designed and fabricated an underwater acoustic carpet cloak using transformation acoustics, a scientific first.
The research was published online in Scientific Reports on April 6.
An acoustic cloak is a material shell that can control the propagation direction of sound waves to make a target undetectable in an acoustic system. The carpet cloak modifies the acoustic signature of the target and mimics the acoustic field obtained from a reflecting plane, so that the cloaked target is indistinguishable from the reflecting surface.
The field of transformation acoustics focuses on the design of new acoustic structures. It shows how to control the propagation of acoustic waves. The parameters of the cloak shell can be given by transformation acoustics.
However, in most cases, these parameters are too complex for practical use. To solve this problem, YANG Jun and his IOA team adopted a scaling factor and simplified the structure of the carpet cloak with only modest impedance mismatch.
The research team then used layers of brass plates featuring small channels filled with water to construct the model cloak. This material possesses effective anisotropic mass density in long-wavelength regimes.
The structure of the carpet cloak, comprised of layered brass plates, is therefore simplified at the cost of some impedance match. "The carpet cloak has a unit cell size of about 1/40 of the wavelength, making it able to control underwater acoustic waves in the deep subwavelength scale," said YANG Jun.
The proposed carpet cloak has shown good performance in experimental results across a wide frequency range. In tests, a short Gaussian pulse propagates towards a target bump covered with the carpet cloak; the scattered wave then returns in the backscattering direction.
The cloaked object successfully mimics the reflecting plane and is imperceptible to sound detection.
Previously, the IOA researchers had designed and fabricated a carpet cloak in air. The results of this earlier research were published in the Journal of Applied Physics (Volume 113, Issue 2, January 2013).
YANG Jun | EurekAlert!
Watching atoms move in hybrid perovskite crystals reveals clues to improving solar cells
22.11.2017 | University of California - San Diego
Fine felted nanotubes: CAU research team develops new composite material made of carbon nanotubes
22.11.2017 | Christian-Albrechts-Universität zu Kiel
Heat from the friction of rocks caused by tidal forces could be the “engine” for the hydrothermal activity on Saturn's moon Enceladus. This presupposes that...
The WHO reports an estimated 429,000 malaria deaths each year. The disease mostly affects tropical and subtropical regions and in particular the African continent. The Fraunhofer Institute for Silicate Research ISC teamed up with the Fraunhofer Institute for Molecular Biology and Applied Ecology IME and the Institute of Tropical Medicine at the University of Tübingen for a new test method to detect malaria parasites in blood. The idea of the research project “NanoFRET” is to develop a highly sensitive and reliable rapid diagnostic test so that patient treatment can begin as early as possible.
Malaria is caused by parasites transmitted by mosquito bite. The most dangerous form of malaria is malaria tropica. Left untreated, it is fatal in most cases....
The formation of stars in distant galaxies is still largely unexplored. For the first time, astron-omers at the University of Geneva have now been able to closely observe a star system six billion light-years away. In doing so, they are confirming earlier simulations made by the University of Zurich. One special effect is made possible by the multiple reflections of images that run through the cosmos like a snake.
Today, astronomers have a pretty accurate idea of how stars were formed in the recent cosmic past. But do these laws also apply to older galaxies? For around a...
Just because someone is smart and well-motivated doesn't mean he or she can learn the visual skills needed to excel at tasks like matching fingerprints, interpreting medical X-rays, keeping track of aircraft on radar displays or forensic face matching.
That is the implication of a new study which shows for the first time that there is a broad range of differences in people's visual ability and that these...
Computer Tomography (CT) is a standard procedure in hospitals, but so far, the technology has not been suitable for imaging extremely small objects. In PNAS, a team from the Technical University of Munich (TUM) describes a Nano-CT device that creates three-dimensional x-ray images at resolutions up to 100 nanometers. The first test application: Together with colleagues from the University of Kassel and Helmholtz-Zentrum Geesthacht the researchers analyzed the locomotory system of a velvet worm.
During a CT analysis, the object under investigation is x-rayed and a detector measures the respective amount of radiation absorbed from various angles....
15.11.2017 | Event News
15.11.2017 | Event News
30.10.2017 | Event News
23.11.2017 | Information Technology
23.11.2017 | Physics and Astronomy
23.11.2017 | Life Sciences