12,635 research outputs found
Full transmission through perfect-conductor subwavelength hole arrays
Light transmission through 2D subwavelength hole arrays in perfect-conductor
films is shown to be complete (100%) at some resonant wavelengths even for
arbitrarily narrow holes. Conversely, the reflection on a 2D planar array of
non-absorbing scatterers is shown to be complete at some wavelengths regardless
how weak the scatterers are. These results are proven analytically and
corroborated by rigorous numerical solution of Maxwell's equations. This work
supports the central role played by dynamical diffraction during light
transmission through subwavelength hole arrays and it provides a systematics to
analyze more complex geometries and many of the features observed in connection
with transmission through hole arrays.Comment: 5 pages, 4 figure
Two-sided asymmetric subduction; implications for tectonomagmatic and metallogenic evolution of the Lut Block, Eastern Iran
West directed subduction zones show common characteristics, such as low structural elevation, deep trench, steep slab and a
conjugate back-arc basin that are opposite to those of the east directed subduction zones. The tectonomagmatic and
metallogenic setting of the Lut Block is still a matter of debate and several hypotheses have been put forward. Despite some
authors denying the influence of the operation of Benioff planes, the majority propose that it occurred beneath the Afghan
Block, while others consider that oceanic lithosphere was dragged under the Lut Block. Cu-Au porphyry deposits seem to
occur in an island arc geotectonic setting during the middle Eocene while Mo-bearing deposits are coincident with the
crustal thickening during Oligocene. We introduce new trace element and isotope geochemical data for granitoids and
structural evidences testifying the two-sided asymmetric subduction beneath both Afghan and Lut Blocks, with different
rates of consumption of oceanic lithosphere
From sensorimotor dependencies to perceptual practices: making enactivism social
Proponents of enactivism should be interested in exploring what notion of action best captures the type of action-perception link that the view proposes, such that it covers all the aspects in which our doings constitute and are constituted by our perceiving. This article proposes and defends the thesis that the notion of sensorimotor dependencies is insufficient to account for the reality of human perception, and that the central enactive notion should be that of perceptual practices. Sensorimotor enactivism is insufficient because it has no traction on socially dependent perceptions, which are essential to the role and significance of perception in our lives. Since the social dimension is a central desideratum in a theory of human perception, enactivism needs a notion that accounts for such an aspect. This article sketches the main features of the Wittgenstein-inspired notion of perceptual practices as the central notion to understand perception. Perception, I claim, is properly understood as woven into a type of social practices that includes food, dance, dress, music, etc. More specifically, perceptual practices are the enactment of culturally structured, normatively rich techniques of commerce of meaningful multi- and inter-modal perceptible material. I argue that perceptual practices explain three central features of socially dependent perception: attentional focus, aspects’ saliency, and modal-specific harmony-like relations
Prospects for direct cosmic ray mass measurements through the Gerasimova-Zatsepin effect
The Solar radiation field may break apart ultra high energy cosmic nuclei,
after which both remnants will be deflected in the interplanetary magnetic
field in different ways. This process is known as the Gerasimova-Zatsepin
effect after its discoverers. We investigate the possibility of using the
detection of the separated air showers produced by a pair of remnant particles
as a way to identify the species of the original cosmic ray primary directly.
Event rates for current and proposed detectors are estimated, and requirements
are defined for ideal detectors of this phenomenon. Detailed computational
models of the disintegration and deflection processes for a wide range of
cosmic ray primaries in the energy range of 10^16 to 10^20 eV are combined with
sophisticated detector models to calculate realistic detection rates. The
fraction of Gerasimova-Zatsepin events is found to be of the order of 10^-5 of
the cosmic ray flux, implying an intrinsic event rate of around 0.07 km^-2
sr^-1 yr^-1 in the energy range defined. Event rates in any real experiment,
however, existing or under construction, will probably not exceed 10^-2 yr^-1.Comment: 4 pages, 4 figure
Directed paths on hierarchical lattices with random sign weights
We study sums of directed paths on a hierarchical lattice where each bond has
either a positive or negative sign with a probability . Such path sums
have been used to model interference effects by hopping electrons in the
strongly localized regime. The advantage of hierarchical lattices is that they
include path crossings, ignored by mean field approaches, while still
permitting analytical treatment. Here, we perform a scaling analysis of the
controversial ``sign transition'' using Monte Carlo sampling, and conclude that
the transition exists and is second order. Furthermore, we make use of exact
moment recursion relations to find that the moments always determine,
uniquely, the probability distribution $P(J)$. We also derive, exactly, the
moment behavior as a function of $p$ in the thermodynamic limit. Extrapolations
($n\to 0$) to obtain for odd and even moments yield a new signal for
the transition that coincides with Monte Carlo simulations. Analysis of high
moments yield interesting ``solitonic'' structures that propagate as a function
of . Finally, we derive the exact probability distribution for path sums
up to length L=64 for all sign probabilities.Comment: 20 pages, 12 figure
One-Dimensional Turbulence Simulations for Reactive Flows in Open and Closed Systems
The One-Dimensional Turbulence (ODT) model is applied to reactive flows in open and closed systems represented by a lifted jet flame in a vitiated coflow, and a constant volume autoignition configuration, respectively. ODT is a one-dimensional model for turbulent flow simulations, which uses a stochastic formulation to represent the effects of turbulent advection. Diffusion and reaction effects along the ODT domain are considered by deterministic evolution equations. This work is an effort to verify the applicability and efficiency of the model for open and closed systems. In the open system case, ODT results are compared against experimental results of a lifted methane/air jet flame detailed in the work of Cabra et al. (2005). In the closed system case, a periodic, constant volume domain is used to investigate the sensitivity of the ignition evolution to initial temperature and composition inhomogeneities of a lean n-heptane/air mixture. In the latter context, ODT results are compared to DNS results from Luong et al. (2015). The results for the jet and constant volume configuration show a reasonable match with the experimental and DNS data, considering the reduced order of the model and the underlying assumptions for each case. At the jet configuration, a dependence of the flame evolution on the turbulence intensity parameter can be seen. For the closed system, initial temperature and composition inhomogeneities allow a mitigation of the undesirable rapid pressure rise due to locally different ignition delay times
Composite mirror facets for ground based gamma ray astronomy
Composite mirrors for gamma-ray astronomy have been developed to fulfill the
specifications required for the next generation of Cherenkov telescopes
represented by CTA (Cherenkov Telescope Array). In addition to the basic
requirements on focus and reflection efficiency, the mirrors have to be stiff,
lightweight, durable and cost efficient. In this paper, the technology
developed to produce such mirrors is described, as well as some tests that have
been performed to validate them. It is shown that these mirrors comply with the
needs of CTA, making them good candidates for use on a significant part of the
array.Comment: 16 pages, 13 figures, accepted to be published on NIM
Absence of a fuzzy phase in the dimensionally reduced 5d Yang-Mills-Chern-Simons model
We perform nonperturbative studies of the dimensionally reduced 5d
Yang-Mills-Chern-Simons model, in which a four-dimensional fuzzy manifold,
``fuzzy S'', is known to exist as a classical solution. Although the
action is unbounded from below, Monte Carlo simulations provide an evidence for
a well-defined vacuum, which stabilizes at large , when the coefficient of
the Chern-Simons term is sufficiently small. The fuzzy S prepared as an
initial configuration decays rapidly into this vacuum in the process of
thermalization. Thus we find that the model does not possess a ``fuzzy S
phase'' in contrast to our previous results on the fuzzy S.Comment: 11 pages, 2 figures, (v2) typos correcte
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