8,199 research outputs found
On the use of bianisotropic huygens' metasurfaces to build leaky-wave antennas
The Electromagnetics AcademyHuygens' metasurfaces are considered a powerful tool to achieve anomalous electromagnetic field transformations. They consist of an artifcial surface built of pairs of collocated electric and magetic dipoles that force the boundary conditions for the desired transformation to be ful lled [1]. Despite their possibilities, the achievable transformations must ful l some conditions. In [2] it was
shown that Huygens' metasurfaces with passive and lossless particles can achieve an arbitrary field transformation provided that the power is conserved at each point of the metasurface and there is wave impedance matching. However, it was shown in [3], that by introducing bianisotropy of the omega-type, the matching condition can be suppressed, which allows the control of both the transmission and rejection coe cients on the metasurface.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech
Experimental Verification of a Leaky-Wave Antenna Based on Bianisotropic Huygens’ Metasurface
Abstract—In this communication, the experimental verification of a leaky-wave antenna that uses a Huygens’ metasurface to have a control on the radiation parameters is addressed. The antenna consists of a parallel-plate waveguide in which the top plate has been replaced by an omega-type bianisotropic Huygens’ metasurface, in order to transform the guided mode into the desired leaky-mode with arbitrary choice of the leakage rates, pointing direction and waveguide height. The physical implementation of the metasurface is explained. Two design examples, radiating at broadside with different leakage factors, are implemented, manufactured and measured. Simulated and experimental results of the achieved directivity, scanning performance and radiation patterns are provided, experimentally corroborating the conceptUniversidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech.
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 706334
Ambiguity, risk and asset returns in continuous time
Existing models in stochastic continuous-time settings assume that beliefs are represented by a probability measure. As illustrated by the Ellsberg Paradox, this feature rules out a priori any concern with ambiguity. This paper formulates a continuous-time intertemporal version of multiple-priors utility, where aversion to ambiguity is admissible. When applied to a representative agent asset market setting, the model delivers restrictions on excess returns that admit interpretations reflecting a premium for risk and a seperate premium for ambiguity.ambiguity, risk, continuous-time, asset returns, Knightian uncertainty, backward stochastic differential equation
Oops! Predicting Unintentional Action in Video
From just a short glance at a video, we can often tell whether a person's
action is intentional or not. Can we train a model to recognize this? We
introduce a dataset of in-the-wild videos of unintentional action, as well as a
suite of tasks for recognizing, localizing, and anticipating its onset. We
train a supervised neural network as a baseline and analyze its performance
compared to human consistency on the tasks. We also investigate self-supervised
representations that leverage natural signals in our dataset, and show the
effectiveness of an approach that uses the intrinsic speed of video to perform
competitively with highly-supervised pretraining. However, a significant gap
between machine and human performance remains. The project website is available
at https://oops.cs.columbia.eduComment: 11 pages, 9 figure
Electrical spin injection from an organic-based ferrimagnet in a hybrid organic/inorganic heterostructure
We report the successful extraction of spin polarized current from the
organic-based room temperature ferrimagnetic semiconductor V[TCNE]x (x~2, TCNE:
tetracyanoethylene; TC ~ 400 K, EG ~ 0.5 eV, s ~ 10-2 S/cm) and its subsequent
injection into a GaAs/AlGaAs light-emitting diode (LED). The spin current
tracks the magnetization of V[TCNE]x~2, is weakly temperature dependent, and
exhibits heavy hole / light hole asymmetry. This result has implications for
room temperature spintronics and the use of inorganic materials to probe spin
physics in organic and molecular systems
A Central Limit Theorem, Loss Aversion and Multi-Armed Bandits
This paper establishes a central limit theorem under the assumption that
conditional variances can vary in a largely unstructured history-dependent way
across experiments subject only to the restriction that they lie in a fixed
interval. Limits take a novel and tractable form, and are expressed in terms of
oscillating Brownian motion. A second contribution is application of this
result to a class of multi-armed bandit problems where the decision-maker is
loss averse
Investment under ambiguity with the best and worst in mind
Recent literature on optimal investment has stressed the difference between the impact of risk and the impact of ambiguity - also called Knightian uncertainty - on investors' decisions. In this paper, we show that a decision maker's attitude towards ambiguity is similarly crucial for investment decisions. We capture the investor's individual ambiguity attitude by applying alpha-MEU preferences to a standard investment problem. We show that the presence of ambiguity often leads to an increase in the subjective project value, and entrepreneurs are more eager to invest. Thereby, our investment model helps to explain differences in investment behavior in situations which are objectively identical
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