2,195 research outputs found
Comparing Evolutionary Operators, Search Spaces, and Evolutionary Algorithms in the Construction of Facial Composites
Facial composite construction is one of the most successful applications of interactive evolutionary computation.
In spite of this, previous work in the area of composite construction has not investigated the
algorithm design options in detail. We address this issue with four experiments. In the first experiment a
sorting task is used to identify the 12 most salient dimensions of a 30-dimensional search space. In the second
experiment the performances of two mutation and two recombination operators for interactive genetic
algorithms are compared. In the third experiment three search spaces are compared: a 30-dimensional
search space, a mathematically reduced 12-dimensional search space, and a 12-dimensional search space
formed from the 12 most salient dimensions. Finally, we compare the performances of an interactive
genetic algorithm to interactive differential evolution. Our results show that the facial composite construction
process is remarkably robust to the choice of evolutionary operator(s), the dimensionality of the search
space, and the choice of interactive evolutionary algorithm. We attribute this to the imprecise nature of human
face perception and differences between the participants in how they interact with the algorithms.
Povzetek: Kompozitna gradnja obrazov je ena izmed najbolj uspešnih aplikacij interaktivnega evolucijskega
ra?cunanja. Kljub temu pa do zdaj na podro?cju kompozitne gradnje niso bile podrobno raziskane
možnosti snovanja algoritma. To vprašanje smo obravnavali s štirimi poskusi. V prvem je uporabljeno
sortiranje za identifikacijo 12 najbolj izstopajo?cih dimenzij 30-dimenzionalnega preiskovalnega prostora.
V drugem primerjamo u?cinkovitost dveh mutacij in dveh rekombinacijskih operaterjev za interaktivni
genetski algoritem. V tretjem primerjamo tri preiskovalne prostore: 30-dimenzionalni, matemati?cno reducirani
12-dimenzionalni in 12-dimenzionalni prostor sestavljen iz 12 najpomembnejših dimenzij. Na
koncu smo primerjali uspešnost interaktivnega genetskega algoritma z interaktivno diferencialno evolucijo.
Rezultati kažejo, da je proces kompozitne gradnje obrazov izredno robusten glede na izbiro evolucijskega
operatorja(-ev), dimenzionalnost preiskovalnega prostora in izbiro interaktivnega evolucijskega algoritma.
To pripisujemo nenatan?cni naravi percepcije in razlikam med interakcijami uporabnikov z algoritmom
Generalised action-angle coordinates defined on island chains
Straight-field-line coordinates are very useful for representing magnetic
fields in toroidally confined plasmas, but fundamental problems arise regarding
their definition in 3-D geometries because of the formation of islands and
chaotic field regions, ie non-integrability. In Hamiltonian dynamical systems
terms these coordinates are a form of action-angle variables, which are
normally defined only for integrable systems. In order to describe 3-D magnetic
field systems, a generalisation of this concept was proposed recently by the
present authors that unified the concepts of ghost surfaces and
quadratic-flux-minimising (QFMin) surfaces. This was based on a simple
canonical transformation generated by a change of variable , where and are poloidal and toroidal
angles, respectively, with a new poloidal angle chosen to give
pseudo-orbits that are a) straight when plotted in the plane and
b) QFMin pseudo-orbits in the transformed coordinate. These two requirements
ensure that the pseudo-orbits are also c) ghost pseudo-orbits. In the present
paper, it is demonstrated that these requirements do not \emph{uniquely}
specify the transformation owing to a relabelling symmetry. A variational
method of solution that removes this lack of uniqueness is proposed.Comment: 10 pages. Accepted by Plasma Physics and Controlled Fusion as part of
a cluster of refereed papers in a special issue containing papers arising
from the Joint International Stellarator & Heliotron Workshop and
Asia-Pacific Plasma Theory Conference, held in Canberra and Murramarang
Resort, Australia, 30 January - 3 February, 201
Interactions of Satellite Galaxies in Cosmological Dark Matter Halos
We present a statistical analysis of the interactions between satellite
galaxies in cosmological dark matter halos taken from fully self-consistent
high-resolution simulations of galaxy clusters. We show that the number
distribution of satellite encounters has a tail that extends to as many as 3-4
encounters per orbit. On average 30% of the substructure population had at
least one encounter (per orbit) with another satellite galaxy. However, this
result depends on the age of the dark matter host halo with a clear trend for
more interactions in younger systems. We also report a correlation between the
number of encounters and the distance of the satellites to the centre of the
cluster: satellite galaxies closer to the centre experience more interactions.
However, this can be simply explained by the radial distribution of the
substructure population and merely reflects the fact that the density of
satellites is higher in those regions.
In order to find substructure galaxies we applied (and present) a new
technique based upon the N-body code MLAPM. This new halo finder MHF
(MLAPM's-Halo-Finder) acts with exactly the same accuracy as the N-body code
itself and is therefore free of any bias and spurious mismatch between
simulation data and halo finding precision related to numerical effects.Comment: 6 pages, 4 figures, accepted by PASA (refereed contribution to the
5th Galactic Chemodynamics workshop, July 2003
Mapping Substructures in Dark Matter Halos
We present a detailed study of the real and integrals-of-motion space
distributions of a satellite obtained from a self-consistent high-resolution
simulation of a galaxy cluster and re-simulated using various analytical halo
potentials. We found that the disrupted satellite appears as a coherent
structure in integrals-of-motion space in all models (``live'' and analytical
potential) although the distribution is significantly smeared for the live host
halo. Further the primary mechanism for this smearing is the mass growth of the
host, which changes both the energy and angular momentum of the satellite
debris. Hence, this must be considered when searching for (stellar) streams
with future observational experiments such as RAVE and GAIA.Comment: 5 pages, 6 figures, MNRAS accepted - minor editing without changing
the conclusions, a high-resolution version of the paper is available from
http://astronomy.swin.edu.au/~sgill/downloads/downloads.htm
Pushing the Boundaries of Spacecraft Autonomy and Resilience with a Custom Software Framework and Onboard Digital Twin
This research addresses the high CubeSat mission failure rates caused by inadequate software and overreliance on ground control. By applying a reliable design methodology to flight software development and developing an onboard digital twin platform with fault prediction capabilities, this study provides a solution to increase satellite resilience and autonomy, thus reducing the risk of mission failure. These findings have implications for spacecraft of all sizes, paving the way for more resilient space missions
Modelling the Marginal Abatement Cost of Mitigating Nitrogen Loss from Agricultural Land
working paperWith the deadline identified by the Water Framework Directive (2000/60/EC)
approaching in 2015 there is increasing pressure on policymakers to introduce new
regulations to achieve water quality targets. Agriculture is one of the contributors of
diffuse pollution entering watercourses and will come under pressure to reduce pollutant
loads. This paper produces Marginal Abatement Cost (MAC) Curves for eight policy
measures that could potentially reduce nitrate leaching from agricultural land on Irish
dairy farms. These include: 1) reduction of fertiliser application by 10%; 2) reduction
of fertiliser application by 20%; 3) livestock unit reduction to limit organic N to 170 kg
ha-1; 4) reduction of livestock units by 20%; 5) change of feed mix to reduce cow
dietary N intake; 6) fencing off watercourses to introduce a buffer zone; 7) improved
dairy cow genetic merit by introducing higher performing dairy breeds; 8) more
efficient slurry application. Results from this study indicate that there will be reductions
in farm gross margins across nearly all policy measures. However, MAC and the
ranking of MAC vary across individual farms and aggregate MAC does not reflect the
heterogeneity of impacts across individual farms. This paper shows that any measure
introduced in a “one size fits all command-control” fashion will not yield efficient
economic results
Cosmology on a Mesh
An adaptive multi grid approach to simulating the formation of structure from
collisionless dark matter is described. MLAPM (Multi-Level Adaptive Particle
Mesh) is one of the most efficient serial codes available on the cosmological
'market' today. As part of Swinburne University's role in the development of
the Square Kilometer Array, we are implementing hydrodynamics, feedback, and
radiative transfer within the MLAPM adaptive mesh, in order to simulate
baryonic processes relevant to the interstellar and intergalactic media at high
redshift. We will outline our progress to date in applying the existing MLAPM
to a study of the decay of satellite galaxies within massive host potentials.Comment: 3 pages, 2 figures, to appear in the proceedings of "The IGM/Galaxy
Connection - The Distribution of Baryons at z=0", ed. M. Putman & J.
Rosenber
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