28 research outputs found
Document Word Clouds: Visualising Web Documents as Tag Clouds to Aid Users in Relevance Decisions
Περιέχει το πλήρες κείμενοInformation Retrieval systems spend a great effort on determining
the significant terms in a document. When, instead, a user
is looking at a document he cannot benefit from such information. He
has to read the text to understand which words are important. In this
paper we take a look at the idea of enhancing the perception of web
documents with visualisation techniques borrowed from the tag clouds
of Web 2.0. Highlighting the important words in a document by using a
larger font size allows to get a quick impression of the relevant concepts
in a text. As this process does not depend on a user query it can also
be used for explorative search. A user study showed, that already simple
TF-IDF values used as notion of word importance helped the users to
decide quicker, whether or not a document is relevant to a topic
Relativistic quantum transport theory of hadronic matter: the coupled nucleon, delta and pion system
We derive the relativistic quantum transport equation for the pion
distribution function based on an effective Lagrangian of the QHD-II model. The
closed time-path Green's function technique, the semi-classical, quasi-particle
and Born approximation are employed in the derivation. Both the mean field and
collision term are derived from the same Lagrangian and presented analytically.
The dynamical equation for the pions is consistent with that for the nucleons
and deltas which we developed before. Thus, we obtain a relativistic transport
model which describes the hadronic matter with , and degrees
of freedom simultaneously. Within this approach, we investigate the medium
effects on the pion dispersion relation as well as the pion absorption and pion
production channels in cold nuclear matter. In contrast to the results of the
non-relativistic model, the pion dispersion relation becomes harder at low
momenta and softer at high momenta as compared to the free one, which is mainly
caused by the relativistic kinetics. The theoretically predicted free cross section is in agreement with the experimental data. Medium
effects on the cross section and momentum-dependent
-decay width are shown to be substantial.Comment: 66 pages, Latex, 12 PostScript figures included; replaced by the
revised version, to appear in Phys. Rev.
Relativistic transport theory of N, \Delta and N^{*}(1440) interacting through , and mesons
A self-consistent relativistic integral-differential equation of the
Boltzmann-Uehling-Uhlenbeck-type for the (1440) resonance is developed
based on an effective Lagrangian of baryons interacting through mesons. The
closed time-path Green's function technique and semi-classical, quasi-particle
and Born approximations are employed in the derivation. The non-equilibrium
RBUU-type equation for the (1440) is consistent with that of nucleon's
and delta's which we derived before. Thus, we obtain a set of coupled equations
for the , and (1440) distribution functions.
All the (1440)-relevant in-medium two-body scattering cross sections
within the , and (1440) system are derived from the same
effective Lagrangian in addition to the mean field and presented analytically,
which can be directly used in the study of relativistic heavy-ion collisions.
The theoretical prediction of the free cross section is
in good agreement with the experimental data. We calculate the in-medium , and cross
sections in cold nuclear matter up to twice the nuclear matter density. The
influence of different choices of the coupling strengths, which
can not be obtained through fitting certain experimental data, are discussed.
The results show that the density dependence of predicted in-medium cross
sections are sensitive to the coupling strengths used. An evident
density dependence will appear when a large scalar coupling strength of
is assumed.Comment: 64 pages, Latex, 13 PostScript figures include
What's new? Analysing language-specific Wikipedia entity contexts to support entity-centric news retrieval
Representation of influential entities, such as celebrities and multinational corporations on the web can vary across languages, re- flecting language-specific entity aspects, as well as divergent views on these entities in different communities. An important source of multilingual background knowledge about influential entities is Wikipedia — an online community-created encyclopaedia — containing more than 280 language editions. Such language-specific information could be applied in entity-centric information retrieval applications, in which users utilise very simple queries, mostly just the entity names, for the relevant documents. In this article we focus on the problem of creating languagespecific entity contexts to support entity-centric, language-specific information retrieval applications. First, we discuss alternative ways such contexts can be built, including Graph-based and Article-based approaches. Second, we analyse the similarities and the differences in these contexts in a case study including 220 entities and five Wikipedia language editions. Third, we propose a context-based entity-centric information retrieval model that maps documents to aspect space, and apply languagespecific entity contexts to perform query expansion. Last, we perform a case study to demonstrate the impact of this model in a news retrieval application. Our study illustrates that the proposed model can effectively improve the recall of entity-centric information retrieval while keeping high precision, and provide language-specific results