7,875 research outputs found
Virtual audio reproduced in a headrest
When virtual audio reproduction is simultaneously required in many seats, such as in aircraft or
cinemas, it may be convenient to use loudspeakers mounted inside each seat's headrest. In
this preliminary study, the feasibility of virtual audio reproduction in the headrest of a single seat
is explored using an inversion technique to compensate for crosstalk and the synthesis of head
related transfer functions. Although large changes in the magnitude of the signals reproduced
at the listener's ears are observed as the listener moves their head within the headrest, informal
listening tests indicate that the reproduced acoustic images are surprisingly stable in about an
eighth of an arc either side of the loudspeaker positions. Not surprisingly, frontal images are
more difficult to reproduce with headrest loudspeakers
Direct neutron capture cross sections of 62Ni in the s-process energy range
Direct neutron capture on 62Ni is calculated in the DWBA and the cross
sections in the energy range relevant for s-process nucleosynthesis are given.
It is confirmed that the thermal value of the capture cross section contains a
subthreshold resonance contribution. Contrary to previous investigations it is
found that the capture at higher energies is dominated by p-waves, thus leading
to a considerably increased cross section at s-process energies and a modified
energy dependence.Comment: 10 pages, 1 figure, corrected typos in Eq. 6 and subsequent paragrap
The light curve of the companion to PSR B1957+20
We present a new analysis of the light curve for the secondary star in the
eclipsing binary millisecond pulsar system PSR B1957+20. Combining previous
data and new data points at minimum from the Hubble Space Telescope, we have
100% coverage in the R-band. We also have a number of new K_s-band data points,
which we use to constrain the infrared magnitude of the system. We model this
with the Eclipsing Light Curve code (ELC). From the modelling with the ELC code
we obtain colour information about the secondary at minimum light in BVRI and
K. For our best fit model we are able to constrain the system inclination to 65
+/- 2 degrees for pulsar masses ranging from 1.3 -- 1.9 M_sun. The pulsar mass
is unconstrained. We also find that the secondary star is not filling its Roche
lobe. The temperature of the un-irradiated side of the companion is in
agreement with previous estimates and we find that the observed temperature
gradient across the secondary star is physically sustainable.Comment: 6 pages, 4 figures & 3tables. Accepted for publication in MNRA
Attractor Metadynamics in Adapting Neural Networks
Slow adaption processes, like synaptic and intrinsic plasticity, abound in
the brain and shape the landscape for the neural dynamics occurring on
substantially faster timescales. At any given time the network is characterized
by a set of internal parameters, which are adapting continuously, albeit
slowly. This set of parameters defines the number and the location of the
respective adiabatic attractors. The slow evolution of network parameters hence
induces an evolving attractor landscape, a process which we term attractor
metadynamics. We study the nature of the metadynamics of the attractor
landscape for several continuous-time autonomous model networks. We find both
first- and second-order changes in the location of adiabatic attractors and
argue that the study of the continuously evolving attractor landscape
constitutes a powerful tool for understanding the overall development of the
neural dynamics
Excitons in Electrostatic Traps
We consider in-plane electrostatic traps for indirect excitons in coupled
quantum wells, where the traps are formed by a laterally modulated gate
voltage. An intrinsic obstacle for exciton confinement in electrostatic traps
is an in-plane electric field that can lead to exciton dissociation. We propose
a design to suppress the in-plane electric field and, at the same time, to
effectively confine excitons in the electrostatic traps. We present
calculations for various classes of electrostatic traps and experimental proof
of principle for trapping of indirect excitons in electrostatic traps.Comment: 4 pages, 3 figure
A Possible Hidden Population of Spherical Planetary Nebulae
We argue that relative to non-spherical planetary nebulae (PNs), spherical
PNs are about an order of magnitude less likely to be detected, at distances of
several kiloparsecs. Noting the structure similarity of halos around
non-spherical PNs to that of observed spherical PNs, we assume that most
unobserved spherical PNs are also similar in structure to the spherical halos
around non-spherical PNs. The fraction of non-spherical PNs with detected
spherical halos around them, taken from a recent study, leads us to the claim
of a large (relative to that of non-spherical PNs) hidden population of
spherical PNs in the visible band. Building a toy model for the luminosity
evolution of PNs, we show that the claimed detection fraction of spherical PNs
based on halos around non-spherical PNs, is compatible with observational
sensitivities. We use this result to update earlier studies on the different PN
shaping routes in the binary model. We estimate that ~30% of all PNs are
spherical, namely, their progenitors did not interact with any binary
companion. This fraction is to be compared with the ~3% fraction of observed
spherical PNs among all observed PNs. From all PNs, ~15% owe their moderate
elliptical shape to the interaction of their progenitors with planets, while
\~55% of all PNs owe their elliptical or bipolar shapes to the interaction of
their progenitors with stellar companions.Comment: AJ, in pres
Distribution-free stochastic model updating with staircase density functions
In stochastic model updating, hybrid uncertainties are typically characterized by the distributional p-box. It assigns a certain probability distribution to model parameters and assumes its hyper-parameters as interval values. Thus, regardless of the updating method employed, the distribution family needs to be known a priori to parameterize the distribution. Meanwhile, a novel class of the random variable, called staircase random variable, can discretely approximate a wide range of distributions by solving moment-matching optimization problem. The first author and his co-workers have recently developed a distribution-free stochastic updating framework, in which model parameters are considered as staircase random variables and their hyper-parameters are inferred in a Bayesian fashion. This framework can explore an optimal distribution from a broad range of potential distributions according to the available data. This study aims to further demonstrate the capability of this framework through a simple numerical example with a parameter following various types of distributions
The eventization of leisure and the strange death of alternative Leeds
The communicative potential of city spaces as leisure spaces is a central assumption of political activism and the creation of alternative, counter-cultural and subcultural scenes. However, such potential for city spaces is limited by the gentrification, privatization and eventization of city centres in the wake of wider societal and cultural struggles over leisure, work and identity formation. In this paper, we present research on alternative scenes in the city of Leeds to argue that the eventization of the city centre has led to a marginalization and of alternative scenes on the fringes of the city. Such marginalization has not caused the death of alternative Leeds or political activism associated with those scenesâbut it has changed the leisure spaces (physical, political and social) in which alternative scenes contest the mainstream
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