111,290 research outputs found
Extended path-indexing
The performance of a theorem prover crucially depends on the speed of the basic retrieval operations, such as finding terms that are unifiable with (instances of, or more general than) some query term. Among the known indexing methods for term retrieval in deduction systems, Path--Indexing exhibits a good performance in general. However, as Path--Indexing is not a perfect filter, the candidates found by this method have still to be subjected to a unification algorithm in order to detect occur--check failures and indirect clashes. As perfect filters, discrimination trees and abstraction trees thus outperform Path--Indexing in some cases. We present an improved version of Path--Indexing that provides both the query trees and the Path--Index with indirect clash an occur--check information. Thus compared to the standard method we dismiss much more terms as possible candidates
Phase retrieval via non-rigid image registration
Phase retrieval is the numerical procedure of recovering a complex-valued
signal from knowledge about its amplitude and some additional information.
Here, an indirect registration procedure, based on the large deformation
diffeomorphic metric mapping (LDDMM) formalism, is investigated as a phase
retrieval method for coherent diffractive imaging. The method attempts to find
a deformation which transforms an initial, template image to match an unknown
target image by comparing the diffraction pattern to the data. The exterior
calculus framework is used to treat different types of deformations in a
unified and coordinate-free way. The algorithm performance with respect to
measurement noise, image topology, and particular action are explored through
numerical examples
Constraining the Physical Properties of Near-Earth Object 2009 BD
We report on Spitzer Space Telescope IRAC observations of near-Earth object
(NEO) 2009 BD that were carried out in support of the NASA Asteroid Robotic
Retrieval Mission (ARRM) concept. We did not detect 2009 BD in 25 hrs of
integration at 4.5 micron. Based on an upper-limit flux density determination
from our data, we present a probabilistic derivation of the physical properties
of this object. The analysis is based on the combination of a thermophysical
model with an orbital model accounting for the non-gravitational forces acting
upon the body. We find two physically possible solutions. The first solution
shows 2009 BD as a 2.9+/-0.3 m diameter rocky body (rho = 2.9+/-0.5 g cm-3)
with an extremely high albedo of 0.85(+0.20/-0.10) that is covered with
regolith-like material, causing it to exhibit a low thermal inertia (Gamma =
30(+20/-10) SI units). The second solution suggests 2009 BD to be a 4+/-1 m
diameter asteroid with pV = 0.45(+0.35/-0.15) that consists of a collection of
individual bare rock slabs (Gamma = 2000+/-1000 SI units, rho = 1.7(+0.7/-0.4)
g cm-3). We are unable to rule out either solution based on physical reasoning.
2009 BD is the smallest asteroid for which physical properties have been
constrained, in this case using an indirect method and based on a detection
limit, providing unique information on the physical properties of objects in
the size range smaller than 10 m.Comment: 28 pages, 8 figures, accepted for publication in Ap
Finding More Relevance: Propagating Similarity on Markov Random Field for Image Retrieval
To effectively retrieve objects from large corpus with high accuracy is a
challenge task. In this paper, we propose a method that propagates visual
feature level similarities on a Markov random field (MRF) to obtain a high
level correspondence in image space for image pairs. The proposed
correspondence between image pair reflects not only the similarity of low-level
visual features but also the relations built through other images in the
database and it can be easily integrated into the existing
bag-of-visual-words(BoW) based systems to reduce the missing rate. We evaluate
our method on the standard Oxford-5K, Oxford-105K and Paris-6K dataset. The
experiment results show that the proposed method significantly improves the
retrieval accuracy on three datasets and exceeds the current state-of-the-art
retrieval performance
A document management methodology based on similarity contents
The advent of the WWW and distributed information systems have made it possible to share documents between different users and organisations. However, this has created many problems related to the security, accessibility, right and most importantly the consistency of documents. It is important that the people involved in the documents management process have access to the most up-to-date version of documents, retrieve the correct documents and should be able to update the documents repository in such a way that his or her document are known to others. In this paper we propose a method for organising, storing and retrieving documents based on similarity contents. The method uses techniques based on information retrieval, document indexation and term extraction and indexing. This methodology is developed for the E-Cognos project which aims at developing tools for the management and sharing of documents in the construction domain
Thin liquid water clouds: their importance and our challenge
Many clouds important to the Earth’s energy balance contain small amounts of liquid water, yet despite many improvements, large differences in retrievals of their liquid water amount and particle size still must be resolved
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