5,500 research outputs found
Twisted Radio Waves and Twisted Thermodynamics
We present and analyze a gedanken experiment and show that the assumption
that an antenna operating at a single frequency can transmit more than two
independent information channels to the far field violates the Second Law of
Thermodynamics. Transmission of a large number of channels, each associated
with an angular momentum "twisted wave" mode, to the far field in free space is
therefore not possible.Comment: Final version, accepted for publication in PLoS ON
Decision support model for the selection of asphalt wearing courses in highly trafficked roads
The suitable choice of the materials forming the wearing course of highly trafficked roads is a delicate task because of their direct interaction with vehicles. Furthermore, modern roads must be planned according to sustainable development goals, which is complex because some of these might be in conflict. Under this premise, this paper develops a multi-criteria decision support model based on the analytic hierarchy process and the technique for order of preference by similarity to ideal solution to facilitate the selection of wearing courses in European countries. Variables were modelled using either fuzzy logic or Monte Carlo methods, depending on their nature. The views of a panel of experts on the problem were collected and processed using the generalized reduced gradient algorithm and a distance-based aggregation approach. The results showed a clear preponderance by stone mastic asphalt over the remaining alternatives in different scenarios evaluated through sensitivity analysis. The research leading to these results was framed in the European FP7 Project DURABROADS (No. 605404).The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007–2013) under Grant Agreement No. 605404
Carbon Nanotube Based Bearing for Rotational Motions
We report the fabrication of a nanoelectromechanical system consisting of a
plate rotating around a multiwalled nanotube bearing. The motion is possible
thanks to the low intershell friction. Indeed, the nanotube has been engineered
so that the sliding happens between different shells. The plate rotation is
activated electrostatically with stator electrodes. The static friction force
is estimated at N/\AA.Comment: 4 pages, 3 figure
Diffraction of Ultrasonic Waves by Elliptical Cracks in Metals
Ultrasonic spectrum analysis is used to study the frequency and angular behavior of diffracted longitudinal waves from elliptical cracks with arbitrary orientation in diffusion bonded titanium alloy. The aspect ratio of the cracks (ratio of major to minor axis) ranged from 1 to 8 and the bandwidth of the input signal was such that the scattering diameter was ka ≥ l. The experimental data are analyzed based on a recently developed elastodynamic diffraction theory (by Achenbach et al.). Some of the key parameters of the scattering data are identified to address the inverse problem
Early occipital sensitivity to syntactic category is based on form typicality
Syntactic factors can rapidly affect behavioral and neural responses during language processing; however, the mechanisms that allow this rapid extraction of syntactically relevant information remain poorly understood. We addressed this issue using magnetoencephalography and found that an unexpected word category (e.g., “The recently princess . . . ”) elicits enhanced activity in visual cortex as early as 120 ms after exposure, and that this activity occurs as a function of the compatibility of a word’s form with the form properties associated with a predicted word category. Because no sensitivity to linguistic factors has been previously reported for words in isolation at this stage of visual analysis, we propose that predictions about upcoming syntactic categories are translated into form-based estimates, which are made available to sensory cortices. This finding may be a key component to elucidating the mechanisms that allow the extreme rapidity and efficiency of language comprehension
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