9,903 research outputs found
Adaptive Sentence Boundary Disambiguation
Labeling of sentence boundaries is a necessary prerequisite for many natural
language processing tasks, including part-of-speech tagging and sentence
alignment. End-of-sentence punctuation marks are ambiguous; to disambiguate
them most systems use brittle, special-purpose regular expression grammars and
exception rules. As an alternative, we have developed an efficient, trainable
algorithm that uses a lexicon with part-of-speech probabilities and a
feed-forward neural network. After training for less than one minute, the
method correctly labels over 98.5\% of sentence boundaries in a corpus of over
27,000 sentence-boundary marks. We show the method to be efficient and easily
adaptable to different text genres, including single-case texts.Comment: This is a Latex version of the previously submitted ps file
(formatted as a uuencoded gz-compressed .tar file created by csh script). The
software from the work described in this paper is available by contacting
[email protected]
Statutory protection of freshwater flora and fauna
The aim of this paper is to summarize the present legislation aimed at protecting freshwater species in Britain, and briefly to review its effectiveness. Some areas have been deliberately omitted, such as fisheries legislation designed to conserve stocks, and the statutory protection of birds associated with fresh waters which forms a large subject area in its own right
Character Education and Its Parallels to Biblical Morality
This paper includes both historical and present day examinations of the state of public education and character in students. Written for the benefit of Christian youth ministers, this paper examines some of the common tenants of modern day character education and seeks to demonstrate their Biblical parallels. Issues regarding the state of character in students and legality of people in a religious profession on a school campus are examined. This paper demonstrates without question that a Christian person can readily support a character education program in the public schools because of the Biblical basis for the values espoused. After examining the evidence it should also provide a youth minister with a better understanding of the acceptable verbiage to use to gain more consistent access to a public school campus
A Laboratory Demonstration of High-Resolution Hard X-ray and Gamma-ray Imaging using Fourier-Transform Techniques
A laboratory imaging system has been developed to study the use of Fourier-transform techniques in high-resolution hard x-ray and γ-ray imaging, with particular emphasis on possible applications to high-energy astronomy. We discuss considerations for the design of a Fourier-transform imager and describe the instrumentation used in the laboratory studies. Several analysis methods for image reconstruction are discussed including the CLEAN algorithm and maximum entropy methods. Images obtained using these methods are presented
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Historical reconstruction of the Atlantic Meridional Overturning Circulation from the ECMWF operational ocean reanalysis
A reconstruction of the Atlantic Meridional Overturning Circulation (MOC) for the period 1959–2006 has been derived from the ECMWF operational ocean reanalysis. The reconstruction shows a wide range of time-variability, including a downward trend. At 26N, both the MOC intensity and changes in its vertical structure are in good agreement with previous estimates based on trans-Atlantic surveys. At 50N, the MOC and strength of the subpolar gyre are correlated at interannual time scales, but show opposite secular trends. Heat transport variability is highly correlated with the MOC but shows a smaller trend due to the warming of the upper ocean, which partially compensates for the weakening of the circulation. Results from sensitivity experiments show that although the time-varying upper boundary forcing provides useful MOC information, the sequential assimilation of ocean data further improves the MOC estimation by increasing both the mean and the time variability
Gamma-ray Bursts, Classified Physically
From Galactic binary sources, to extragalactic magnetized neutron stars, to
long-duration GRBs without associated supernovae, the types of sources we now
believe capable of producing bursts of gamma-rays continues to grow apace. With
this emergent diversity comes the recognition that the traditional (and newly
formulated) high-energy observables used for identifying sub-classes does not
provide an adequate one-to-one mapping to progenitors. The popular
classification of some > 100 sec duration GRBs as ``short bursts'' is not only
an unpalatable retronym and syntactically oxymoronic but highlights the
difficultly of using what was once a purely phenomenological classification to
encode our understanding of the physics that gives rise to the events. Here we
propose a physically based classification scheme designed to coexist with the
phenomenological system already in place and argue for its utility and
necessity.Comment: 6 pages, 3 figures. Slightly expanded version of solicited paper to
be published in the Proceedings of ''Gamma Ray Bursts 2007,'' Santa Fe, New
Mexico, November 5-9. Edited by E. E. Fenimore, M. Galassi, D. Palme
Functional biases in GRB's spectral parameter correlations
Gamma Ray Bursts (GRBs) show evidence of different spectral shapes, light
curves, duration, host galaxies and they explode within a wide redshift range.
However, the most of them seems to follow very tight correlations among some
observed quantities relating to their energetic. If true, these correlations
have significant implications on burst physics, giving constraints on
theoretical models. Moreover, several suggestions have been made to use these
correlations in order to calibrate GRBs as standard candles and to constrain
the cosmological parameters. We investigate the cosmological relation between
low energy index in GRBs prompt spectra and the redshift . We
present a statistical analysis of the relation between the total isotropic
energy and the peak energy (also known as Amati relation) in
GRBs spectra searching for possible functional biases. Possible implications on
the vs relation of the vs correlation are
evaluated. We used MonteCarlo simulations and the boostrap method to evaluate
how large are the effects of functional biases on the vs . We
show that high values of the linear correlation coefficent, up to about 0.8, in
the vs relation are obtained for random generated samples of
GRBs, confirming the relevance of functional biases. Astrophysical consequences
from vs relation are then to be revised after a more accurate
and possibly bias free analysis.Comment: 6 pages, 6 figures, conference poster session: "070228: The Next
Decade of Gamma-Ray Burst Afterglows", Amsterdam, March 2007, MNRAS submitte
GRBs and the thermalization process of electron-positron plasmas
We discuss the temporal evolution of the pair plasma created in Gamma-Ray
Burst sources. A particular attention is paid to the relaxation of the plasma
into thermal equilibrium. We also discuss the connection between the dynamics
of expansion and the spatial geometry of the plasma. The role of the baryonic
loading parameter is emphasized.Comment: 4 pages, 3 figures, in the Proceedings of the "Gamma Ray Bursts 2007"
meeting, November 5-9, 2007, Santa Fe, New Mexico, US
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