160 research outputs found
Simulating the use of macro-actions through action reordering
The use of macro-actions in planning introduces a trade-off.. Macro-actions can offer search guidance by suggesting sequences of actions; but can potentially make search more expensive by increasing the branching factor. In this paper we present a technique for simulating the use of macro actions by altering the order in which actions are considered for application during enforced hill-climbing search. Actions are ordered based on the number of times they have occurred, in past solution plans, following the last action added to the plan. We demonstrate that the action-reordering technique used can offer improved search performance without the negative performance impacts often observed when using macro-actions
Planning in probabilistic domains using a deterministic numeric planner
In the probabilistic track of the IPC5 - the last International planning competitions - a probabilistic planner based on combining deterministic planning with replanning - FF-REPLAN - out performed the other competitors. This probabilistic planning paradigm discarded the probabilistic information of the domain, just considering for each action its nominal effect as a deterministic effect
Monitoring Oyster Point seagrasses : 1995 to 1999
In the present report, an assessment of changes in seagrass distribution and
abundance since the baseline (November 1995) and previous monitoring surveys of
December 1997 and November 1998 is included. We provide a quantification of
changes between years and comment on the possible impacts of the dredging
program
Baseline survey of Hinchinbrook region seagrasses - October (spring) 1996
Current coastal zone management issues in the Hinchinbrook region include protection of
fisheries habitats, dugong habitat areas and increases in aquaculture, agriculture and tourist
operations. A regional coastal management plan which is being developed, also requires
detailed information on seagrass resources for the coastal zone from Dunk Island in the north,
to Cleveland Bay in the south. Decreases in estimates of dugong abundance in the southern
half of the Great Barrier Reef region since the 1980's have also prompted the need for
detailed baseline and monitoring surveys of seagrasses in this and other regions
Optical‐mode structure of micropillar microcavities containing a fluorescent conjugated polymer
The light emission from a series of micropillar microcavities containing a fluorescent, red‐emitting conjugated polymer, is explored. Cavities are fabricated by defining two dielectric mirrors either side of a polymer active region. Focused ion‐beam (FIB) lithography is then used to etch pillar structures into the planar cavity having diameters between 1 and 11 µm. The photoluminescence (PL) emission of the cavities is characterized using real‐space tomographic and Fourier‐space imaging techniques, with emission shown to be quantized into a mode‐structure resulting from both vertical and lateral optical confinement within the pillar. The optical‐confinement effects which result in a blue‐shift of the fundamental mode as the pillar diameter is reduced is demonstrated, with a model applied to describe the energy and distribution of the confined optical modes
The Void Abundance with Non-Gaussian Primordial Perturbations
We use a Press-Schechter-like calculation to study how the abundance of voids
changes in models with non-Gaussian initial conditions. While a positive
skewness increases the cluster abundance, a negative skewness does the same for
the void abundance. We determine the dependence of the void abundance on the
non-Gaussianity parameter fnl for the local-model bispectrum-which approximates
the bispectrum in some multi-field inflation models-and for the equilateral
bispectrum, which approximates the bispectrum in e.g. string-inspired DBI
models of inflation. We show that the void abundance in large-scale-structure
surveys currently being considered should probe values as small as fnl < 10 and
fnl^eq < 30, over distance scales ~10 Mpc.Comment: Submitted to JCA
Understanding Galaxy Formation and Evolution
The old dream of integrating into one the study of micro and macrocosmos is
now a reality. Cosmology, astrophysics, and particle physics intersect in a
scenario (but still not a theory) of cosmic structure formation and evolution
called Lambda Cold Dark Matter (LCDM) model. This scenario emerged mainly to
explain the origin of galaxies. In these lecture notes, I first present a
review of the main galaxy properties, highlighting the questions that any
theory of galaxy formation should explain. Then, the cosmological framework and
the main aspects of primordial perturbation generation and evolution are
pedagogically detached. Next, I focus on the ``dark side'' of galaxy formation,
presenting a review on LCDM halo assembling and properties, and on the main
candidates for non-baryonic dark matter. It is shown how the nature of
elemental particles can influence on the features of galaxies and their
systems. Finally, the complex processes of baryon dissipation inside the
non-linearly evolving CDM halos, formation of disks and spheroids, and
transformation of gas into stars are briefly described, remarking on the
possibility of a few driving factors and parameters able to explain the main
body of galaxy properties. A summary and a discussion of some of the issues and
open problems of the LCDM paradigm are given in the final part of these notes.Comment: 50 pages, 10 low-resolution figures (for normal-resolution, DOWNLOAD
THE PAPER (PDF, 1.9 Mb) FROM http://www.astroscu.unam.mx/~avila/avila.pdf).
Lectures given at the IV Mexican School of Astrophysics, July 18-25, 2005
(submitted to the Editors on March 15, 2006
Liquid–liquid phase separation morphologies in ultra-white beetle scales and a synthetic equivalent
Cyphochilus beetle scales are amongst the brightest structural whites in nature, being highly opacifying whilst extremely thin. However, the formation mechanism for the voided intra-scale structure is unknown. Here we report 3D x-ray nanotomography data for the voided chitin networks of intact white scales of Cyphochilus and Lepidiota stigma. Chitin-filling fractions are found to be 31 ± 2% for Cyphochilus and 34 ± 1% for Lepidiota stigma, indicating previous measurements overestimated their density. Optical simulations using finite-difference time domain for the chitin morphologies and simulated Cahn-Hilliard spinodal structures show excellent agreement. Reflectance curves spanning filling fraction of 5-95% for simulated spinodal structures, pinpoint optimal whiteness for 25% chitin filling. We make a simulacrum from a polymer undergoing a strong solvent quench, resulting in highly reflective (~94%) white films. In-situ X-ray scattering confirms the nanostructure is formed through spinodal decomposition phase separation. We conclude that the ultra-white beetle scale nanostructure is made via liquid–liquid phase separation
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