35,052 research outputs found
Acquiring Correct Knowledge for Natural Language Generation
Natural language generation (NLG) systems are computer software systems that
produce texts in English and other human languages, often from non-linguistic
input data. NLG systems, like most AI systems, need substantial amounts of
knowledge. However, our experience in two NLG projects suggests that it is
difficult to acquire correct knowledge for NLG systems; indeed, every knowledge
acquisition (KA) technique we tried had significant problems. In general terms,
these problems were due to the complexity, novelty, and poorly understood
nature of the tasks our systems attempted, and were worsened by the fact that
people write so differently. This meant in particular that corpus-based KA
approaches suffered because it was impossible to assemble a sizable corpus of
high-quality consistent manually written texts in our domains; and structured
expert-oriented KA techniques suffered because experts disagreed and because we
could not get enough information about special and unusual cases to build
robust systems. We believe that such problems are likely to affect many other
NLG systems as well. In the long term, we hope that new KA techniques may
emerge to help NLG system builders. In the shorter term, we believe that
understanding how individual KA techniques can fail, and using a mixture of
different KA techniques with different strengths and weaknesses, can help
developers acquire NLG knowledge that is mostly correct
Soil sustainability in organic agricultural production
Traditionally, the assessment of soil sustainability and the potential impact of cultivation are based upon the application of chemical procedures. In the absence of a biological context, these measurements offer little in understanding longterm changes in soil husbandry. Detailed microcosm investigations were applied as a predictive tool for management change. The microcosms were designed with homogenised soils treated with organic amendments. Key soil functional relationships were quantified using stable isotope techniques, biochemical measurements and traditional approaches
The Mandelstam-Leibbrandt Prescription in Light-Cone Quantized Gauge Theories
Quantization of gauge theories on characteristic surfaces and in the
light-cone gauge is discussed. Implementation of the Mandelstam-Leibbrandt
prescription for the spurious singularity is shown to require two distinct null
planes, with independent degrees of freedom initialized on each. The relation
of this theory to the usual light-cone formulation of gauge field theory, using
a single null plane, is described. A connection is established between this
formalism and a recently given operator solution to the Schwinger model in the
light-cone gauge.Comment: Revtex, 14 pages. One postscript figure (requires psfig). A brief
discussion of necessary restrictions on the light-cone current operators has
been added, and two references. Final version to appear in Z. Phys.
On the wake of a Darrieus turbine
The theory and experimental measurements on the aerodynamic decay of a wake from high performance vertical axis wind turbine are discussed. In the initial experimental study, the wake downstream of a model Darrieus rotor, 28 cm diameter and a height of 45.5 cm, was measured in a Boundary Layer Wind Tunnel. The wind turbine was run at the design tip speed ratio of 5.5. It was found that the wake decayed at a slower rate with distance downstream of the turbine, than a wake from a screen with similar troposkein shape and drag force characteristics as the Darrieus rotor. The initial wind tunnel results indicated that the vertical axis wind turbines should be spaced at least forty diameters apart to avoid mutual power depreciation greater than ten per cent
Squeezing out the last 1 nanometer of water: A detailed nanomechanical study
In this study, we present a detailed analysis of the squeeze-out dynamics of
nanoconfined water confined between two hydrophilic surfaces measured by
small-amplitude dynamic atomic force microscopy (AFM). Explicitly considering
the instantaneous tip-surface separation during squeezeout, we confirm the
existence of an adsorbed molecular water layer on mica and at least two
hydration layers. We also confirm the previous observation of a sharp
transition in the viscoelastic response of the nanoconfined water as the
compression rate is increased beyond a critical value (previously determined to
be about 0.8 nm/s). We find that below the critical value, the tip passes
smoothly through the molecular layers of the film, while above the critical
speed, the tip encounters "pinning" at separations where the film is able to
temporarily order. Pre-ordering of the film is accompanied by increased force
fluctuations, which lead to increased damping preceding a peak in the film
stiffness once ordering is completed. We analyze the data using both
Kelvin-Voigt and Maxwell viscoelastic models. This provides a complementary
picture of the viscoelastic response of the confined water film
Non-recursive max* operator with reduced implementation complexity for turbo decoding
In this study, the authors deal with the problem of how to effectively approximate the max?? operator when having n > 2 input values, with the aim of reducing implementation complexity of conventional Log-MAP turbo decoders. They show that, contrary to previous approaches, it is not necessary to apply the max?? operator recursively over pairs of values. Instead, a simple, yet effective, solution for the max?? operator is revealed having the advantage of being in non-recursive form and thus, requiring less computational effort. Hardware synthesis results for practical turbo decoders have shown implementation savings for the proposed method against the most recent published efficient turbo decoding algorithms by providing near optimal bit error rate (BER) performance
Probabilistic models of information retrieval based on measuring the divergence from randomness
We introduce and create a framework for deriving probabilistic models of Information Retrieval. The models are nonparametric models of IR obtained in the language model approach. We derive term-weighting models by measuring the divergence of the actual term distribution from that obtained under a random process. Among the random processes we study the binomial distribution and Bose--Einstein statistics. We define two types of term frequency normalization for tuning term weights in the document--query matching process. The first normalization assumes that documents have the same length and measures the information gain with the observed term once it has been accepted as a good descriptor of the observed document. The second normalization is related to the document length and to other statistics. These two normalization methods are applied to the basic models in succession to obtain weighting formulae. Results show that our framework produces different nonparametric models forming baseline alternatives to the standard tf-idf model
On the Impact of Entity Linking in Microblog Real-Time Filtering
Microblogging is a model of content sharing in which the temporal locality of
posts with respect to important events, either of foreseeable or unforeseeable
nature, makes applica- tions of real-time filtering of great practical
interest. We propose the use of Entity Linking (EL) in order to improve the
retrieval effectiveness, by enriching the representation of microblog posts and
filtering queries. EL is the process of recognizing in an unstructured text the
mention of relevant entities described in a knowledge base. EL of short pieces
of text is a difficult task, but it is also a scenario in which the information
EL adds to the text can have a substantial impact on the retrieval process. We
implement a start-of-the-art filtering method, based on the best systems from
the TREC Microblog track realtime adhoc retrieval and filtering tasks , and
extend it with a Wikipedia-based EL method. Results show that the use of EL
significantly improves over non-EL based versions of the filtering methods.Comment: 6 pages, 1 figure, 1 table. SAC 2015, Salamanca, Spain - April 13 -
17, 201
Pupil remapping for high contrast astronomy: results from an optical testbed
The direct imaging and characterization of Earth-like planets is among the
most sought-after prizes in contemporary astrophysics, however current optical
instrumentation delivers insufficient dynamic range to overcome the vast
contrast differential between the planet and its host star. New opportunities
are offered by coherent single mode fibers, whose technological development has
been motivated by the needs of the telecom industry in the near infrared. This
paper presents a new vision for an instrument using coherent waveguides to
remap the pupil geometry of the telescope. It would (i) inject the full pupil
of the telescope into an array of single mode fibers, (ii) rearrange the pupil
so fringes can be accurately measured, and (iii) permit image reconstruction so
that atmospheric blurring can be totally removed. Here we present a laboratory
experiment whose goal was to validate the theoretical concepts underpinning our
proposed method. We successfully confirmed that we can retrieve the image of a
simulated astrophysical object (in this case a binary star) though a pupil
remapping instrument using single mode fibers.Comment: Accepted in Optics Expres
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