86,915 research outputs found
Developments in GRworkbench
The software tool GRworkbench is an ongoing project in visual, numerical
General Relativity at The Australian National University. Recently, GRworkbench
has been significantly extended to facilitate numerical experimentation in
analytically-defined space-times. The numerical differential geometric engine
has been rewritten using functional programming techniques, enabling objects
which are normally defined as functions in the formalism of differential
geometry and General Relativity to be directly represented as function
variables in the C++ code of GRworkbench. The new functional differential
geometric engine allows for more accurate and efficient visualisation of
objects in space-times and makes new, efficient computational techniques
available. Motivated by the desire to investigate a recent scientific claim
using GRworkbench, new tools for numerical experimentation have been
implemented, allowing for the simulation of complex physical situations.Comment: 14 pages. To appear A. Moylan, S.M. Scott and A.C. Searle,
Developments in GRworkbench. Proceedings of the Tenth Marcel Grossmann
Meeting on General Relativity, editors M. Novello, S. Perez-Bergliaffa and R.
Ruffini. Singapore: World Scientific 200
Differences in intention to use educational RSS feeds between Lebanese and British students: A multiâgroup analysis based on the technology acceptance model
Really Simple Syndication (RSS) offers a means for university students to receive timely updates from virtual learning environments. However, despite its utility, only 21% of home students surveyed at a university in Lebanon claim to have ever used the technology. To investigate whether national culture could be an influence on intention to use RSS, the survey was extended to British students in the UK. Using the Technology Adoption Model (TAM) as a research framework, 437 students responded to a questionnaire containing four constructs: behavioral intention to use; attitude towards benefit; perceived usefulness; and perceived ease of use. Principle components analysis and structural equation modelling were used to explore the psychometric qualities and utility of TAM in both contexts. The results show that adoption was significantly higher, but also modest, in the British context at 36%. Configural and metric invariance were fully supported, while scalar and factorial invariance were partially supported. Further analysis shows significant differences between perceived usefulness and perceived ease of use across the two contexts studied. Therefore, it is recommended that faculty demonstrate to students how educational RSS feeds can be used effectively to increase awareness and emphasize usefulness in both contexts
General properties of cosmological models with an Isotropic Singularity
Much of the published work regarding the Isotropic Singularity is performed
under the assumption that the matter source for the cosmological model is a
barotropic perfect fluid, or even a perfect fluid with a -law equation
of state. There are, however, some general properties of cosmological models
which admit an Isotropic Singularity, irrespective of the matter source. In
particular, we show that the Isotropic Singularity is a point-like singularity
and that vacuum space-times cannot admit an Isotropic Singularity. The
relationships between the Isotropic Singularity, and the energy conditions, and
the Hubble parameter is explored. A review of work by the authors, regarding
the Isotropic Singularity, is presented.Comment: 18 pages, 1 figur
A Resource-Based View Of International Human Resources: Toward A Framework of Integrative and Creative Capabilities
Drawing on organizational learning and MNC perspectives, we extend the resource-based view to address how international human resource management provides sustainable competitive advantage. We develop a framework that emphasizes and extends traditional assumptions of the resource-based view by identifying the learning capabilities necessary for a complex and changing global environment. These capabilities address how MNCs might both create new HR practices in response to local environments and integrate existing HR practices from other parts of the firm (affiliates, regional headquarters, and global headquarters). In an effort to understand the nature of such capabilities, we discuss aspects of human capital, social capital, and organizational capital that might be linked to their development. Page
Stable and Efficient Structures for the Content Production and Consumption in Information Communities
Real-world information communities exhibit inherent structures that
characterize a system that is stable and efficient for content production and
consumption. In this paper, we study such structures through mathematical
modelling and analysis. We formulate a generic model of a community in which
each member decides how they allocate their time between content production and
consumption with the objective of maximizing their individual reward. We define
the community system as "stable and efficient" when a Nash equilibrium is
reached while the social welfare of the community is maximized. We investigate
the conditions for forming a stable and efficient community under two
variations of the model representing different internal relational structures
of the community. Our analysis results show that the structure with "a small
core of celebrity producers" is the optimally stable and efficient for a
community. These analysis results provide possible explanations to the
sociological observations such as "the Law of the Few" and also provide
insights into how to effectively build and maintain the structure of
information communities.Comment: 21 page
Quantum signatures of breather-breather interactions
The spectrum of the Quantum Discrete Nonlinear Schr\"odinger equation on a
periodic 1D lattice shows some interesting detailed band structure which may be
interpreted as the quantum signature of a two-breather interaction in the
classical case. We show that this fine structure can be interpreted using
degenerate perturbation theory.Comment: 4 pages, 4 fig
Impact of layer defects in ferroelectric thin films
Based on a modified Ising model in a transverse field we demonstrate that
defect layers in ferroelectric thin films, such as layers with impurities,
vacancies or dislocations, are able to induce a strong increase or decrease of
the polarization depending on the variation of the exchange interaction within
the defect layers. A Green's function technique enables us to calculate the
polarization, the excitation energy and the critical temperature of the
material with structural defects. Numerically we find the polarization as
function of temperature, film thickness and the interaction strengths between
the layers. The theoretical results are in reasonable accordance to
experimental datas of different ferroelectric thin films.Comment: 17 pages, 8 figure
Enhancing Practice and Achievement in Introductory Programming With a Robot Olympics
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A note on behaviour at an isotropic singularity
The behaviour of Jacobi fields along a time-like geodesic running into an
isotropic singularity is studied. It is shown that the Jacobi fields are
crushed to zero length at a rate which is the same in every direction
orthogonal to the geodesic. We show by means of a counter-example that this
crushing effect depends crucially on a technicality of the definition of
isotropic singularities, and not just on the uniform degeneracy of the metric
at the singularity.Comment: 13 pp. plain latex. To appear in Classical and Quantum Gravit
Longitude : a privacy-preserving location sharing protocol for mobile applications
Location sharing services are becoming increasingly popular. Although many location sharing services allow users to set up privacy policies to control who can access their location, the use made by service providers remains a source of concern. Ideally, location sharing providers and middleware should not be able to access usersâ location data without their consent. In this paper, we propose a new location sharing protocol called Longitude that eases privacy concerns by making it possible to share a userâs location data blindly and allowing the user to control who can access her location, when and to what degree of precision. The underlying cryptographic algorithms are designed for GPS-enabled mobile phones. We describe and evaluate our implementation for the Nexus One Android mobile phone
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