472 research outputs found
17 ways to say yes:Toward nuanced tone of voice in AAC and speech technology
People with complex communication needs who use speech-generating devices have very little expressive control over their tone of voice. Despite its importance in human interaction, the issue of tone of voice remains all but absent from AAC research and development however. In this paper, we describe three interdisciplinary projects, past, present and future: The critical design collection Six Speaking Chairs has provoked deeper discussion and inspired a social model of tone of voice; the speculative concept Speech Hedge illustrates challenges and opportunities in designing more expressive user interfaces; the pilot project Tonetable could enable participatory research and seed a research network around tone of voice. We speculate that more radical interactions might expand frontiers of AAC and disrupt speech technology as a whole
Realistic clocks, universal decoherence and the black hole information paradox
Ordinary quantum mechanics is formulated on the basis of the existence of an
ideal classical clock external to the system under study. This is clearly an
idealization. As emphasized originally by Salecker and Wigner and more recently
by other authors, there exist limits in nature to how ``classical'' even the
best possible clock can be. When one introduces realistic clocks, quantum
mechanics ceases to be unitary and a fundamental mechanism of decoherence of
quantum states arises. We estimate the rate of universal loss of unitarity
using optimal realistic clocks. In particular we observe that the rate is rapid
enough to eliminate the black hole information puzzle: all information is lost
through the fundamental decoherence before the black hole can evaporate. This
improves on a previous calculation we presented with a sub-optimal clock in
which only part of the information was lost by the time of evaporation.Comment: 3 Pages, RevTex, no figure
Canonical quantization of general relativity in discrete space-times
It has long been recognized that lattice gauge theory formulations, when
applied to general relativity, conflict with the invariance of the theory under
diffeomorphisms. Additionally, the traditional lattice field theory approach
consists in fixing the gauge in a Euclidean action, which does not appear
appropriate for general relativity. We analyze discrete lattice general
relativity and develop a canonical formalism that allows to treat constrained
theories in Lorentzian signature space-times. The presence of the lattice
introduces a ``dynamical gauge'' fixing that makes the quantization of the
theories conceptually clear, albeit computationally involved. Among other
issues the problem of a consistent algebra of constraints is automatically
solved in our approach. The approach works successfully in other field theories
as well, including topological theories like BF theory. We discuss a simple
cosmological application that exhibits the quantum elimination of the
singularity at the big bang.Comment: 4 pages, RevTeX, no figures, final version to appear in Physical
Review Letter
Fatigue strength of austempered ductile iron-to-steel dissimilar arc-welded joints
Nowadays, the use of different classes of materials in the same structure is increased to keep pace with innovation and high structural performances. In this context, structural components made of different materials need to be joined together and a possible solution is given by arc welding. Dissimilar welded joints must often be able to withstand fatigue loads; however, Design Standards provide fatigue strength categories only for homogeneous welded joints. The aim of the present paper is to compare the fatigue behaviour of EN-GJS-1050 austempered ductile iron-to-S355J2 steel dissimilar joints to the categories of the corresponding homogeneous steel welded joints, as suggested in International Standards and Recommendations. For this purpose, experimental fatigue tests were performed on a selection of dissimilar welded details. First, the microstructure was identified by metallographic analysis; micro-hardness measurements were collected and residual stress profiles were obtained by using the X-ray diffraction technique on a selection of joints. Misalignments were quantified for all specimens. Then, experimental fatigue tests have been performed on a number of joint geometries subject to axial or bending fatigue loadings and tested in the as-welded conditions. The fracture surfaces of the joints have been analysed to locate fatigue crack nucleation sites
Evaluation of design recommendations for the development of wheelchair rugby sports-wear
Currently, wheelchair rugby athletes face the challenges of playing the sport without specifically designed sports-wear kit. A few designs and recommendations have already been proposed by researchers but none have made it to market yet. The purpose of this study was to evaluate a set of design recommendations for the development of wheelchair rugby sports-wear. This was done so that the products to be created are developed in collaboration with their potential users, responding to their particular needs and requirements. The evaluation was done through an online survey, where the athletes were presented with a visual representation of the design recommendations. The results indicate that the people questioned agree with the majority of the proposed designs and would be happy to have these improvements made to their current sports-wear. The most criticised recommendations were for the gloves, as they are the most important part of the kit, so it is important that they are adequate and allow for a good performance
Close limit evolution of Kerr-Schild type initial data for binary black holes
We evolve the binary black hole initial data family proposed by Bishop {\em
et al.} in the limit in which the black holes are close to each other. We
present an exact solution of the linearized initial value problem based on
their proposal and make use of a recently introduced generalized formalism for
studying perturbations of Schwarzschild black holes in arbitrary coordinates to
perform the evolution. We clarify the meaning of the free parameters of the
initial data family through the results for the radiated energy and waveforms
from the black hole collision.Comment: 8 pages, RevTex, four eps figure
Loop Quantum Geometry: A primer
This is the written version of a lecture given at the ``VI Mexican School of
Gravitation and Mathematical Physics" (Nov 21-27, 2004, Playa del Carmen,
Mexico), introducing the basics of Loop Quantum Geometry. The purpose of the
written contribution is to provide a Primer version, that is, a first entry
into Loop Quantum Gravity and to present at the same time a friendly guide to
the existing pedagogical literature on the subject. This account is geared
towards graduate students and non-experts interested in learning the basics of
the subject.Comment: 25 pages. Contribution for the Proceedings of the VI Mexican School
of Gravitation and Mathematical Physics. Corrected typo
No black hole information puzzle in a relational universe
The introduction of a relational time in quantum gravity naturally implies
that pure quantum states evolve into mixed quantum states. We show, using a
recently proposed concrete implementation, that the rate at which pure states
naturally evolve into mixed ones is faster than that due to collapsing into a
black hole that later evaporates. This is rather remarkable since the
fundamental mechanism for decoherence is usually very weak. Therefore the
``black hole information puzzle'' is rendered de-facto unobservable.Comment: 4 pages, no figures, revte
Perturbative evolution of conformally flat initial data for a single boosted black hole
The conformally flat families of initial data typically used in numerical
relativity to represent boosted black holes are not those of a boosted slice of
the Schwarzschild spacetime. If such data are used for each black hole in a
collision, the emitted radiation will be partially due to the ``relaxation'' of
the individual holes to ``boosted Schwarzschild'' form. We attempt to compute
this radiation by treating the geometry for a single boosted conformally flat
hole as a perturbation of a Schwarzschild black hole, which requires the use of
second order perturbation theory. In this we attempt to mimic a previous
calculation we did for the conformally flat initial data for spinning holes. We
find that the boosted black hole case presents additional subtleties, and
although one can evolve perturbatively and compute radiated energies, it is
much less clear than in the spinning case how useful for the study of
collisions are the radiation estimates for the ``spurious energy'' in each
hole. In addition to this we draw some lessons on which frame of reference
appears as more favorable for computing black hole collisions in the close
limit approximation.Comment: 11 pages, RevTex, 4 figures included with psfig, to appear in PR
The Lazarus Project. II. Spacelike extraction with the quasi-Kinnersley tetrad
The Lazarus project was designed to make the most of limited 3D binary
black-hole simulations, through the identification of perturbations at late
times, and subsequent evolution of the Weyl scalar via the Teukolsky
formulation. Here we report on new developments, employing the concept of the
``quasi-Kinnersley'' (transverse) frame, valid in the full nonlinear regime, to
analyze late-time numerical spacetimes that should differ only slightly from
Kerr. This allows us to extract the essential information about the background
Kerr solution, and through this, to identify the radiation present. We
explicitly test this procedure with full numerical evolutions of Bowen-York
data for single spinning black holes, head-on and orbiting black holes near the
ISCO regime. These techniques can be compared with previous Lazarus results,
providing a measure of the numerical-tetrad errors intrinsic to the method, and
give as a by-product a more robust wave extraction method for numerical
relativity.Comment: 17 pages, 10 figures. Journal version with text changes, revised
figures. [Note updated version of original Lazarus paper (gr-qc/0104063)
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