13,036 research outputs found
Challenging Ubiquitous Inverted Files
Stand-alone ranking systems based on highly optimized inverted file structures are generally considered ‘the’ solution for building search engines. Observing various developments in software and hardware, we argue however that IR research faces a complex engineering problem in the quest for more flexible yet efficient retrieval systems. We propose to base the development of retrieval systems on ‘the database approach’: mapping high-level declarative specifications of the retrieval process into efficient query plans. We present the Mirror DBMS as a prototype implementation of a retrieval system based on this approach
Infrared Eclipses of the Strongly Irradiated Planet WASP-33b, and Oscillations of its Host Star
We observe two secondary eclipses of the strongly irradiated transiting
planet WASP-33b in the Ks band, and one secondary eclipse each at 3.6- and 4.5
microns using Warm Spitzer. This planet orbits an A5V delta-Scuti star that is
known to exhibit low amplitude non-radial p-mode oscillations at about
0.1-percent semi-amplitude. We detect stellar oscillations in all of our
infrared eclipse data, and also in one night of observations at J-band out of
eclipse. The oscillation amplitude, in all infrared bands except Ks, is about
the same as in the optical. However, the stellar oscillations in Ks band have
about twice the amplitude as seen in the optical, possibly because the
Brackett-gamma line falls in this bandpass. We use our best-fit values for the
eclipse depth, as well as the 0.9 micron eclipse observed by Smith et al., to
explore possible states of the exoplanetary atmosphere, based on the method of
Madhusudhan and Seager. On this basis we find two possible states for the
atmospheric structure of WASP-33b. One possibility is a non-inverted
temperature structure in spite of the strong irradiance, but this model
requires an enhanced carbon abundance (C/O>1). The alternative model has solar
composition, but an inverted temperature structure. Spectroscopy of the planet
at secondary eclipse, using a spectral resolution that can resolve the water
vapor band structure, should be able to break the degeneracy between these very
different possible states of the exoplanetary atmosphere. However, both of
those model atmospheres absorb nearly all of the stellar irradiance with
minimal longitudinal re-distribution of energy, strengthening the hypothesis of
Cowan et al. that the most strongly irradiated planets circulate energy poorly.
Our measurement of the central phase of the eclipse yields e*cos(omega)=0.0003
+/-0.00013, which we regard as being consistent with a circular orbit.Comment: 23 pages, 9 figures, 3 tables, accepted for the Astrophysical Journa
Automated Video Analysis of Animal Movements Using Gabor Orientation Filters
To quantify locomotory behavior, tools for determining the location and shape of an animal’s body are a first requirement. Video recording is a convenient technology to store raw movement data, but extracting body coordinates from video recordings is a nontrivial task. The algorithm described in this paper solves this task for videos of leeches or other quasi-linear animals in a manner inspired by the mammalian visual processing system: the video frames are fed through a bank of Gabor filters, which locally detect segments of the animal at a particular orientation. The algorithm assumes that the image location with maximal filter output lies on the animal’s body and traces its shape out in both directions from there. The algorithm successfully extracted location and shape information from video clips of swimming leeches, as well as from still photographs of swimming and crawling snakes. A Matlab implementation with a graphical user interface is available online, and should make this algorithm conveniently usable in many other contexts
Preserving the impossible: conservation of soft-sediment hominin footprint sites and strategies for three-dimensional digital data capture.
Human footprints provide some of the most publically emotive and tangible evidence of our ancestors. To the scientific community they provide evidence of stature, presence, behaviour and in the case of early hominins potential evidence with respect to the evolution of gait. While rare in the geological record the number of footprint sites has increased in recent years along with the analytical tools available for their study. Many of these sites are at risk from rapid erosion, including the Ileret footprints in northern Kenya which are second only in age to those at Laetoli (Tanzania). Unlithified, soft-sediment footprint sites such these pose a significant geoconservation challenge. In the first part of this paper conservation and preservation options are explored leading to the conclusion that to 'record and digitally rescue' provides the only viable approach. Key to such strategies is the increasing availability of three-dimensional data capture either via optical laser scanning and/or digital photogrammetry. Within the discipline there is a developing schism between those that favour one approach over the other and a requirement from geoconservationists and the scientific community for some form of objective appraisal of these alternatives is necessary. Consequently in the second part of this paper we evaluate these alternative approaches and the role they can play in a 'record and digitally rescue' conservation strategy. Using modern footprint data, digital models created via optical laser scanning are compared to those generated by state-of-the-art photogrammetry. Both methods give comparable although subtly different results. This data is evaluated alongside a review of field deployment issues to provide guidance to the community with respect to the factors which need to be considered in digital conservation of human/hominin footprints
Unsupervised Domain Adaptation GAN Inversion for Image Editing
Existing GAN inversion methods work brilliantly for high-quality image
reconstruction and editing while struggling with finding the corresponding
high-quality images for low-quality inputs. Therefore, recent works are
directed toward leveraging the supervision of paired high-quality and
low-quality images for inversion. However, these methods are infeasible in
real-world scenarios and further hinder performance improvement. In this paper,
we resolve this problem by introducing Unsupervised Domain Adaptation (UDA)
into the Inversion process, namely UDA-Inversion, for both high-quality and
low-quality image inversion and editing. Particularly, UDA-Inversion first
regards the high-quality and low-quality images as the source domain and
unlabeled target domain, respectively. Then, a discrepancy function is
presented to measure the difference between two domains, after which we
minimize the source error and the discrepancy between the distributions of two
domains in the latent space to obtain accurate latent codes for low-quality
images. Without direct supervision, constructive representations of
high-quality images can be spontaneously learned and transformed into
low-quality images based on unsupervised domain adaptation. Experimental
results indicate that UDA-inversion is the first that achieves a comparable
level of performance with supervised methods in low-quality images across
multiple domain datasets. We hope this work provides a unique inspiration for
latent embedding distributions in image process tasks
Hiding in the Shadows II: Collisional Dust as Exoplanet Markers
Observations of the youngest planets (1-10 Myr for a transitional disk)
will increase the accuracy of our planet formation models. Unfortunately,
observations of such planets are challenging and time-consuming to undertake
even in ideal circumstances. Therefore, we propose the determination of a set
of markers that can pre-select promising exoplanet-hosting candidate disks. To
this end, N-body simulations were conducted to investigate the effect of an
embedded Jupiter mass planet on the dynamics of the surrounding planetesimal
disk and the resulting creation of second generation collisional dust. We use a
new collision model that allows fragmentation and erosion of planetesimals, and
dust-sized fragments are simulated in a post process step including
non-gravitational forces due to stellar radiation and a gaseous protoplanetary
disk. Synthetic images from our numerical simulations show a bright double ring
at 850 m for a low eccentricity planet, whereas a high eccentricity planet
would produce a characteristic inner ring with asymmetries in the disk. In the
presence of first generation primordial dust these markers would be difficult
to detect far from the orbit of the embedded planet, but would be detectable
inside a gap of planetary origin in a transitional disk.Comment: Accepted for publication in Ap
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