528 research outputs found
Combining Models of Approximation with Partial Learning
In Gold's framework of inductive inference, the model of partial learning
requires the learner to output exactly one correct index for the target object
and only the target object infinitely often. Since infinitely many of the
learner's hypotheses may be incorrect, it is not obvious whether a partial
learner can be modifed to "approximate" the target object.
Fulk and Jain (Approximate inference and scientific method. Information and
Computation 114(2):179--191, 1994) introduced a model of approximate learning
of recursive functions. The present work extends their research and solves an
open problem of Fulk and Jain by showing that there is a learner which
approximates and partially identifies every recursive function by outputting a
sequence of hypotheses which, in addition, are also almost all finite variants
of the target function.
The subsequent study is dedicated to the question how these findings
generalise to the learning of r.e. languages from positive data. Here three
variants of approximate learning will be introduced and investigated with
respect to the question whether they can be combined with partial learning.
Following the line of Fulk and Jain's research, further investigations provide
conditions under which partial language learners can eventually output only
finite variants of the target language. The combinabilities of other partial
learning criteria will also be briefly studied.Comment: 28 page
A Map of Update Constraints in Inductive Inference
We investigate how different learning restrictions reduce learning power and
how the different restrictions relate to one another. We give a complete map
for nine different restrictions both for the cases of complete information
learning and set-driven learning. This completes the picture for these
well-studied \emph{delayable} learning restrictions. A further insight is
gained by different characterizations of \emph{conservative} learning in terms
of variants of \emph{cautious} learning.
Our analyses greatly benefit from general theorems we give, for example
showing that learners with exclusively delayable restrictions can always be
assumed total.Comment: fixed a mistake in Theorem 21, result is the sam
Oscillator Strengths for B-X, C-X, and E-X Transitions in Carbon Monoxide
Band oscillator strengths for electronic transitions in CO were obtained at
the Synchrotron Radiation Center of the University of Wisconsin-Madison. Our
focus was on transitions that are observed in interstellar spectra with the Far
Ultraviolet Spectroscopic Explorer; these transitions are also important in
studies of selective isotope photodissociation where fractionation among
isotopomers can occur. Absorption from the ground state (X ^1Sigma^+ v'' = 0)
to A ^1Pi (v'= 5), B ^1Sigma^+ (v' = 0, 1), C ^1Sigma^+ (v' = 0, 1), and E ^1Pi
(v' = 0) was measured. Fits to the A - X (5, 0) band, whose oscillator strength
is well known, yielded the necessary column density and excitation temperature.
These parameters were used in a least-squares fit of the observed profiles for
the transitions of interest to extract their band oscillator strengths. Our
oscillator strengths are in excellent agreement with results from recent
experiments using a variety of techniques. This agreement provides the basis
for a self-consistent set of f-values at far ultraviolet wavelengths for
studies of interstellar (and stellar) CO.Comment: 22 pages, 3 figures, ApJS (in press
Physical Activity and Immunity in HIV-Infected Individuals
The purpose of this study was to determine what relationship exists among physical activity levels and viral load and CD4+ cell count in HIV-infected individuals. Increased viral load is associated with disease progression and symptom severity. A convenience sample of 66 male and female subjects between the ages of 18 and 64 years of age (mean 399/8) was recruited from a hospital-based HIV/AIDS clinic. Components of PA were assessed for three continuous days using a mini-motion logger wrist actigraph. These components included mean PA level, and PA index and acceleration index. Pearson’s correlational analysis was used to test the strength of association between PA components and viral load or CD4+ cell count. A significant inverse relationship was found between mean PA level and viral load (p=0.047). An inverse relationship was also observed between PA index and viral load (p=0.0061). Neither mean PA nor PA index scores correlated with CD4+ cell counts. Acceleration index, a measure of PA intensity, showed no correlation to viral load or CD4+ cell counts. These findings suggest that increasing levels of physical activity might have beneficial effects on viral load in HIV-infected individuals
An examination of the effects of self-regulatory focus on the perception of the media richness: the case of email
Communication is a key element in organizations’ business success. The media richness theory and the channel expansion theory are two of the most influential theories regarding the selection and use of communication media in organizations; however, literature has focused little on the effects of self-regulation by managers and employees in these theories. To analyze these topics, this study develops an empirical investigation by gathering data from 600 managers and employees using a questionnaire. The results suggest that the perception of media richness is positively affected when the individual shows a promotion focus or strategy.Peer ReviewedPostprint (author’s final draft
Requirements for IT Governance in Organizations Experiencing Decentralization
International audienceDecentralization of organizations and subsequent change of their management and operation styles require changes in organization's processes and heavily involve IT. Enterprise Architecture (EA) frameworks fit to primarily centralized organizational structures, and as such have shortcomings when used in decentralized organizations. We illustrate this idea on the example of one organization in the Higher Education sector that faces decentralization of its structure and has to adapt to it. Overcoming these challenges requires some new principles to be introduced and incorporated into the EA knowledge. In particular for IT governance, in this study we argue that peer-to-peer principles can offer more suitable governance over current EA frameworks as they are able to better align with decentralized components of an organizational structure
Emergent organization and responsive technologies in crisis: Creating connections or enabling divides
I articulate and employ a situational boundary-making approach to study the emergence of organization and technology at a shelter during Hurricane Katrina. My analysis of qualitative data shows how emergent organization occurred at the shelter as situational entanglements consisting of three main elements: a salient moment in time, key actors, and boundary-making practices. Key actors' responses to salient moments in time enacted both distinction and dependency between organizational and technological actors, resulting in a divided organization. This analysis extends emergent approaches by showing how organization and technology are situationally organized and emerges through the (in)determinacy of meaning. Implications are also discussed for disaster managers to assess the success and failure of technology during a response. © The Author(s) 2012
On the accumulation of planetesimals near disc gaps created by protoplanets
We have performed three-dimensional two-fluid (gas-dust) hydrodynamical
models of circumstellar discs with embedded protoplanets (3 - 333 M\oplu) and
small solid bodies (radii 10cm to 10m). We find that high mass planets (\gtrsim
Saturn mass) open sufficiently deep gaps in the gas disc such that the density
maximum at the outer edge of the gap can very efficiently trap metre-sized
solid bodies. This allows the accumulation of solids at the outer edge of the
gap as solids from large radii spiral inwards to the trapping region. This
process of accumulation occurs fastest for those bodies that spiral inwards
most rapidly, typically metre-sized boulders, whilst smaller and larger objects
will not migrate sufficiently rapidly in the discs lifetime to benefit from the
process. Around a Jupiter mass planet we find that bound clumps of solid
material, as large as several Earth masses, may form, potentially collapsing
under self-gravity to form planets or planetesimals. These results are in
agreement with Lyra et al. (2009), supporting their finding that the formation
of a second generation of planetesimals or of terrestrial mass planets may be
triggered by the presence of a high mass planet.Comment: 14 pages, 10 figures. Accepted for publication in MNRA
Information and Communication Technology (ICT) and International Business Travel: Mobility Allies?
Like forecasts about the paperless office, technological solutions to the problem of international business travel continue to be deferred. As with the increased use of office paper, international business travel is defying predictions of its decline. There is growing evidence to suggest that business sectors which seem ideally placed to substitute information and communication technology (ICT) for travel, are actually generating more physical travel than other sectors. This paper develops a case study of the Irish software industry to exemplify why international travel is not diminishing in importance how and the ICT and business travel relationship is changing in this sector. The paper presents research findings that suggest that a cycle of substitution, generation and modification relationships have occurred as mobility interdependencies have developed.Peer Reviewe
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