21,346 research outputs found
Topological Modelling of Grammatical and Lexical Aspect in English
It is assumed that aspect in both cases â as a process-profiling category â is analogous to the profiling of things and atemporal relations (in the sense of Langacker 1987, 1990, 2000), given the maximisation of the temporal domain in the characterisation of processes (perfective and imperfective, hence: dynamic and stative), and minimalisation of the temporal domain during the conceptualisation of things (conceptually independent entities) and atemporal relations (conceptually dependent atemporal configurations). The analogy between nouns and verbs in terms of âgranularityâ has been so far variously addressed by Langacker (1990), Jackendoff (1991) and Talmy (2001), and also constitutes the core assumption in my research on topological modelling
Bridging the gap: building better tools for game development
The following thesis is about questioning how we design game making tools, and how developers may build easier tools to use. It is about the highlighting the inadequacies of current game making programs as well as introducing Goal-Oriented Design as a possible solution. It is also about the processes of digital product development, and reflecting on the necessity for both design and development methods to work cohesively for meaningful results. Interaction Design is in essence the abstracting of key relations that matter to the contextual environment. The result of attempting to tie the Interaction Design principles, Game Design issues together with Software Development practices has led to the production of the User-Centred game engine, PlayBoard
Specification and Construction of Control Flow Semantics
In this paper we propose a visual language CFSL for specifying control flow semantics of programming languages. We also present a translation from CFSL to graph production systems (GPS) for flow graph construction; that is, any CFSL specification, say for a language L, gives rise to a GPS that constructs from any L-program (represented as an abstract syntax graph) the corresponding flow graph. The specification language is rich enough to capture complex language constructs, including all of Java
Analysis of urban sprawl at mega city Cairo, Egypt using multisensoral remote sensing data, landscape metrics and gradient analysis
This paper is intended to highlight the capabilities
of synergistic usage of remote sensing, landscape metrics and
gradient analysis. We aim to improve the understanding of
spatial characteristics and effects of urbanization on city level.
Multisensoral and multitemporal remotely sensed data sets
from the Landsat and TerraSAR-X sensor enable monitoring
a long time period with area-wide information on the spatial
urban expansion over time. Landscape metrics aim to quantify
patterns on urban footprint level complemented by gradient
analysis giving insight into the spatial developing of spatial
parameters from the urban center to the periphery. The
results paint a characteristic picture of the emerging spatial
urban patterns at mega city Cairo, Egypt since the 1970s
The Connection between Supernova Remnants and the Galactic Magnetic Field: A Global Radio Study of the Axisymmetric Sample
The study of supernova remnants (SNRs) is fundamental to understanding the
chemical enrichment and magnetism in galaxies, including our own Milky Way. In
an effort to understand the connection between the morphology of SNRs and the
Galactic magnetic field (GMF), we have examined the radio images of all known
SNRs in our Galaxy and compiled a large sample that have an "axisymmetric"
morphology, which we define to mean SNRs with a "bilateral" or "barrel"-shaped
morphology, in addition to one-sided shells. We selected the cleanest examples
and model each of these at their appropriate Galactic position using two GMF
models, those of Jansson & Farrar (2012a), which includes a vertical halo
component, and Sun et al. (2008) that is oriented entirely parallel to the
plane. Since the magnitude and relative orientation of the magnetic field
changes with distance from the sun, we analyse a range of distances, from 0.5
to 10 kpc in each case. Using a physically motivated model of a SNR expanding
into the ambient GMF, we find the models using Jansson & Farrar (2012a) are
able to reproduce observed morphologies of many SNRs in our sample. These
results strongly support the presence of an off-plane, vertical component to
the GMF, and the importance of the Galactic field on SNR morphology. Our
approach also provides a potential new method for determining distances to
SNRs, or conversely, distances to features in the large-scale GMF if SNR
distances are known.Comment: 24 pages, 8 figures plus one 5-page appendix figure, 3 tables,
accepted to A&
Finite-Difference and Pseudospectral Time-Domain Methods Applied to Backwards-Wave Metamaterials
Backwards-wave (BW) materials that have simultaneously negative real parts of
their electric permittivity and magnetic permeability can support waves where
phase and power propagation occur in opposite directions. These materials were
predicted to have many unusual electromagnetic properties, among them
amplification of the near-field of a point source, which could lead to the
perfect reconstruction of the source field in an image [J. Pendry, Phys. Rev.
Lett. \textbf{85}, 3966 (2000)]. Often systems containing BW materials are
simulated using the finite-difference time-domain technique. We show that this
technique suffers from a numerical artifact due to its staggered grid that
makes its use in simulations involving BW materials problematic. The
pseudospectral time-domain technique, on the other hand, uses a collocated grid
and is free of this artifact.
It is also shown that when modeling the dispersive BW material, the linear
frequency approximation method introduces error that affects the frequency of
vanishing reflection, while the auxiliary differential equation, the Z
transform, and the bilinear frequency approximation method produce vanishing
reflection at the correct frequency. The case of vanishing reflection is of
particular interest for field reconstruction in imaging applications.Comment: 9 pages, 8 figures, accepted by IEEE Transactions on Antennas and
Propagatio
The orientation and kinematics of inner tidal tails around dwarf galaxies orbiting the Milky Way
Using high-resolution collisionless N-body simulations we study the
properties of tidal tails formed in the immediate vicinity of a two-component
dwarf galaxy evolving in a static potential of the Milky Way (MW). The stellar
component of the dwarf is initially in the form of a disk and the galaxy is
placed on an eccentric orbit motivated by CDM-based cosmological simulations.
We measure the orientation, density and velocity distribution of the stars in
the tails. Due to the geometry of the orbit, in the vicinity of the dwarf,
where the tails are densest and therefore most likely to be detectable, they
are typically oriented towards the MW and not along the orbit. We report on an
interesting phenomenon of `tidal tail flipping': on the way from the pericentre
to the apocentre the old tails following the orbit are dissolved and new ones
pointing towards the MW are formed over a short timescale. We also find a tight
linear relation between the velocity of stars in the tidal tails and their
distance from the dwarf. Using mock data sets we demonstrate that if dwarf
spheroidal (dSph) galaxies in the vicinity of the MW are tidally affected their
kinematic samples are very likely contaminated by tidally stripped stars which
tend to artificially inflate the measured velocity dispersion. The effect is
stronger for dwarfs on their way from the peri- to the apocentre due to the
formation of new tidal tails after pericentre. Realistic mass estimates of dSph
galaxies thus require removal of these stars from kinematic samples.Comment: 8 pages, 7 figures, accepted for publication in MNRA
Dynamic state reconciliation and model-based fault detection for chemical processes
In this paper, we present a method for the fault detection based on the residual generation. The main idea is to reconstruct the outputs of the system from the measurements using the extended Kalman filter. The estimations are compared to the values of the reference model and so, deviations are interpreted as possible faults. The reference model is simulated by the dynamic hybrid simulator, PrODHyS. The use of this method is illustrated through an application in the field of chemical processe
ROAM: a Rich Object Appearance Model with Application to Rotoscoping
Rotoscoping, the detailed delineation of scene elements through a video shot,
is a painstaking task of tremendous importance in professional post-production
pipelines. While pixel-wise segmentation techniques can help for this task,
professional rotoscoping tools rely on parametric curves that offer the artists
a much better interactive control on the definition, editing and manipulation
of the segments of interest. Sticking to this prevalent rotoscoping paradigm,
we propose a novel framework to capture and track the visual aspect of an
arbitrary object in a scene, given a first closed outline of this object. This
model combines a collection of local foreground/background appearance models
spread along the outline, a global appearance model of the enclosed object and
a set of distinctive foreground landmarks. The structure of this rich
appearance model allows simple initialization, efficient iterative optimization
with exact minimization at each step, and on-line adaptation in videos. We
demonstrate qualitatively and quantitatively the merit of this framework
through comparisons with tools based on either dynamic segmentation with a
closed curve or pixel-wise binary labelling
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