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Multimodal and ubiquitous computing systems: supporting independent-living older users
We document the rationale and design of a multimodal interface to a pervasive/ubiquitous computing system that supports independent living by older people in their own homes. The Millennium Home system involves fitting a residentâs home with sensors â these sensors can be used to trigger sequences of interaction with the resident to warn them about dangerous events, or to check if they need external help. We draw lessons from the design process and conclude the paper with implications for the design of multimodal interfaces to ubiquitous systems developed for the elderly and in healthcare, as well as for more general ubiquitous computing applications
Asymmetric scattering by non-hermitian potentials
The scattering of quantum particles by non-hermitian (generally nonlocal)
potentials in one dimension may result in asymmetric transmission and/or
reflection from left and right incidence. Eight generalized symmetries based on
the discrete Klein's four-group (formed by parity, time reversal, their
product, and unity) are used together with generalized unitarity relations to
determine the possible and/or forbidden scattering asymmetries. Six basic
device types are identified when the scattering coefficients (squared moduli of
scattering amplitudes) adopt zero/one values, and transmission and/or
reflection are asymmetric. They can pictorially be described as a one-way
mirror, a one-way barrier (a Maxwell pressure demon), one-way (transmission or
reflection) filters, a mirror with unidirectional transmission, and a
transparent, one-way reflector. We design potentials for these devices and also
demonstrate that the behavior of the scattering coefficients can be extended to
a broad range of incident momenta
Text Production in Bebo: a study of three children's text production in online social networking sites
Full version unavailable due to 3rd party copyright restrictionsFull version unavailable due to 3rd party copyright restrictions.This thesis aims to explore three pre-teenage childrenâs text production in online social networking sites. Social networking is a mainstream youth activity in the UK, conducted by (at the time of writing) almost 50% of 10-12 year old internet users (Ofcom, 2011, p.44). While social networking has been the subject of much interest amongst scholars and policy-makers, little has been published that documents the use of social networking amongst pre-teenage children. The literature that does exist is largely concerned with documenting usage (Ofcom, 2011; Livingstone and Haddon, 2010), and childrenâs safety in these contexts (Department for Children, Schools and Families (DCSF)/Byron 2010; DCSF/Byron, 2008; Livingstone et al., 2011a). This study aims to explore childrenâs text production in social networking sites with rightful regard for this concern, but with a focus on how children behave as text producers in these contexts.
Working from an interpretive qualitative research paradigm, a purposive sample of three children who used (at the time) the popular social networking site Bebo was selected. The children were interviewed using a semi-structured interview schedule three times between June 2008 and May 2009. Interviews were transcribed using a line by line coding method. To support these data and contextualise analysis, screenshots of the childrenâs profile pages were also collected at each interview. Using a constructivist grounded theory approach (Charmaz, 2006), these data were analysed within data sets around each interview incident, and then synthesised to build a case study for each participant. This recursive process involved initial and focused coding, where following the construction of key codes for each data set, the codes were organised under thematic headings and finally used to construct tentative categories that described how the children behaved as text producers. Four tentative categories were constructed to describe the participantsâ behaviour: text production to achieve social positioning; text production to achieve social control; text production to enact a text producing role; and text production for pleasure. Based upon the elaboration of these categories, a model of text production as mastery is proposed. In this model, childrenâs text production is regarded in relation two spectrums of mastery: a spectrum of social control and a spectrum of textual crafting. This study concludes by recommending that the social networking context must be recognised by educators as a meaningful context in which childrenâs mastery of these critical skills can be developed in order that they can they learn to be critical and masterful text producers in the new digital age (Gee, 2011 and Hayes, 2011)
The mass of the b-quark from lattice NRQCD and lattice perturbation theory
We present a determination of the b-quark mass accurate through O(\alpha_s^2)
in perturbation theory and including partial contributions at O(\alpha_s^3).
Nonperturbative input comes from the calculation of the Upsilon and B_s
energies in lattice QCD including the effect of u, d and s sea quarks. We use
an improved NRQCD action for the b-quark. This is combined with the heavy quark
energy shift in NRQCD determined using a mixed approach of high-beta simulation
and automated lattice perturbation theory. Comparison with experiment enables
the quark mass to be extracted: in the MS bar scheme we find m_b(m_b) =
4.166(43) GeV.Comment: v2 - corrected some typos and an error in the summary plo
B-meson decay constants: a more complete picture from full lattice QCD
We extend the picture of -meson decay constants obtained in lattice QCD
beyond those of the , and to give the first full lattice QCD
results for the , and . We use improved NonRelativistic QCD
for the valence quark and the Highly Improved Staggered Quark (HISQ) action
for the lighter quarks on gluon field configurations that include the effect of
, and quarks in the sea with quark masses going down to
physical values. For the ratio of vector to pseudoscalar decay constants, we
find = 0.941(26), = 0.953(23) (both
less than 1.0) and = 0.988(27). Taking correlated
uncertainties into account we see clear indications that the ratio increases as
the mass of the lighter quark increases. We compare our results to those using
the HISQ formalism for all quarks and find good agreement both on decay
constant values when the heaviest quark is a and on the dependence on the
mass of the heaviest quark in the region of the . Finally, we give an
overview plot of decay constants for gold-plated mesons, the most complete
picture of these hadronic parameters to date.Comment: 20 pages, 9 figures. Minor updates to the discussion in several
places and some additional reference
Direct determination of the strange and light quark condensates from full lattice QCD
We determine the strange quark condensate from lattice QCD for the first time and compare its value to that of the light quark and chiral condensates. The results come from a direct calculation of the expectation value of the trace of the quark propagator followed by subtraction of the appropriate perturbative contribution, derived here, to convert the non-normal-ordered mÏÌ
Ï to the MSÌ
scheme at a fixed scale. This is then a well-defined physical ânonperturbativeâ condensate that can be used in the operator product expansion of current-current correlators. The perturbative subtraction is calculated through O(αs) and estimates of higher order terms are included through fitting results at multiple lattice spacing values. The gluon field configurations used are âsecond generationâ ensembles from the MILC collaboration that include 2+1+1 flavors of sea quarks implemented with the highly improved staggered quark action and including u/d sea quarks down to physical masses. Our results are âšsÌ
sâ©MSÌ
(2ââGeV)=-(290(15)ââMeV)3, âšlÌ
lâ©MSÌ
(2ââGeV)=-(283(2)ââMeV)3, where l is a light quark with mass equal to the average of the u and d quarks. The strange to light quark condensate ratio is 1.08(16). The light quark condensate is significantly larger than the chiral condensate in line with expectations from chiral analyses. We discuss the implications of these results for other calculations
Lorentzian spin foam amplitudes: graphical calculus and asymptotics
The amplitude for the 4-simplex in a spin foam model for quantum gravity is
defined using a graphical calculus for the unitary representations of the
Lorentz group. The asymptotics of this amplitude are studied in the limit when
the representation parameters are large, for various cases of boundary data. It
is shown that for boundary data corresponding to a Lorentzian simplex, the
asymptotic formula has two terms, with phase plus or minus the Lorentzian
signature Regge action for the 4-simplex geometry, multiplied by an Immirzi
parameter. Other cases of boundary data are also considered, including a
surprising contribution from Euclidean signature metrics.Comment: 30 pages. v2: references now appear. v3: presentation greatly
improved (particularly diagrammatic calculus). Definition of "Regge state"
now the same as in previous work; signs change in final formula as a result.
v4: two references adde
Effective action and semiclassical limit of spin foam models
We define an effective action for spin foam models of quantum gravity by
adapting the background field method from quantum field theory. We show that
the Regge action is the leading term in the semi-classical expansion of the
spin foam effective action if the vertex amplitude has the large-spin
asymptotics which is proportional to an exponential function of the vertex
Regge action. In the case of the known three-dimensional and four-dimensional
spin foam models this amounts to modifying the vertex amplitude such that the
exponential asymptotics is obtained. In particular, we show that the ELPR/FK
model vertex amplitude can be modified such that the new model is finite and
has the Einstein-Hilbert action as its classical limit. We also calculate the
first-order and some of the second-order quantum corrections in the
semi-classical expansion of the effective action.Comment: Improved presentation, 2 references added. 15 pages, no figure
Canonical path integral measures for Holst and Plebanski gravity. I. Reduced Phase Space Derivation
An important aspect in defining a path integral quantum theory is the
determination of the correct measure. For interacting theories and theories
with constraints, this is non-trivial, and is normally not the heuristic
"Lebesgue measure" usually used. There have been many determinations of a
measure for gravity in the literature, but none for the Palatini or Holst
formulations of gravity. Furthermore, the relations between different resulting
measures for different formulations of gravity are usually not discussed.
In this paper we use the reduced phase technique in order to derive the
path-integral measure for the Palatini and Holst formulation of gravity, which
is different from the Lebesgue measure up to local measure factors which depend
on the spacetime volume element and spatial volume element.
From this path integral for the Holst formulation of GR we can also give a
new derivation of the Plebanski path integral and discover a discrepancy with
the result due to Buffenoir, Henneaux, Noui and Roche (BHNR) whose origin we
resolve. This paper is the first in a series that aims at better understanding
the relation between canonical LQG and the spin foam approach.Comment: 27 pages, minor correction
- âŠ