103,517 research outputs found
An Ontology-Based Recommender System with an Application to the Star Trek Television Franchise
Collaborative filtering based recommender systems have proven to be extremely
successful in settings where user preference data on items is abundant.
However, collaborative filtering algorithms are hindered by their weakness
against the item cold-start problem and general lack of interpretability.
Ontology-based recommender systems exploit hierarchical organizations of users
and items to enhance browsing, recommendation, and profile construction. While
ontology-based approaches address the shortcomings of their collaborative
filtering counterparts, ontological organizations of items can be difficult to
obtain for items that mostly belong to the same category (e.g., television
series episodes). In this paper, we present an ontology-based recommender
system that integrates the knowledge represented in a large ontology of
literary themes to produce fiction content recommendations. The main novelty of
this work is an ontology-based method for computing similarities between items
and its integration with the classical Item-KNN (K-nearest neighbors)
algorithm. As a study case, we evaluated the proposed method against other
approaches by performing the classical rating prediction task on a collection
of Star Trek television series episodes in an item cold-start scenario. This
transverse evaluation provides insights into the utility of different
information resources and methods for the initial stages of recommender system
development. We found our proposed method to be a convenient alternative to
collaborative filtering approaches for collections of mostly similar items,
particularly when other content-based approaches are not applicable or
otherwise unavailable. Aside from the new methods, this paper contributes a
testbed for future research and an online framework to collaboratively extend
the ontology of literary themes to cover other narrative content.Comment: 25 pages, 6 figures, 5 tables, minor revision
Performance Following: Real-Time Prediction of Musical Sequences Without a Score
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Double Parton Scattering, Multi-Parton Interactions, underlying event and identified hadrons: summary of recent results
Recent results related to Double-Parton Scattering (DPS) and Multi-Parton
Interactions (MPI) from the LHC experiments (ALICE, ATLAS, CMS and LHCb) are
reviewed and discussed together with a brief overview of relevant literature.
The robust evidence collected for DPS in different channels at LHC energies is
complemented by an increasing understanding of our description of MPI in high
energy collisions and the corresponding modelling of the underlying event (UE)
in hadronic interactions. Potential new results expected during Run 2 at the
LHC are also anticipated.
The relation and the interplay between the relevant observables for DPS, MPI
and UE analyses are discussed presenting recent attempts to bring together
their description in a single Monte Carlo tune. Identified hadron spectra at
the LHC have been now measured by all collaborations and results are reviewed
with an emphasis on strangeness production and baryon/meson ratio. The data
collected during Run 1 at the LHC with different collision systems (pp, p-Pb,
Pb-Pb) show that several particle production features appear to be more
correlated with the event multiplicity than the collision system itself.Comment: 7 pages, no figures, LHCP2014 conference proceeding
Identifying Unmaintained Projects in GitHub
Background: Open source software has an increasing importance in modern
software development. However, there is also a growing concern on the
sustainability of such projects, which are usually managed by a small number of
developers, frequently working as volunteers. Aims: In this paper, we propose
an approach to identify GitHub projects that are not actively maintained. Our
goal is to alert users about the risks of using these projects and possibly
motivate other developers to assume the maintenance of the projects. Method: We
train machine learning models to identify unmaintained or sparsely maintained
projects, based on a set of features about project activity (commits, forks,
issues, etc). We empirically validate the model with the best performance with
the principal developers of 129 GitHub projects. Results: The proposed machine
learning approach has a precision of 80%, based on the feedback of real open
source developers; and a recall of 96%. We also show that our approach can be
used to assess the risks of projects becoming unmaintained. Conclusions: The
model proposed in this paper can be used by open source users and developers to
identify GitHub projects that are not actively maintained anymore.Comment: Accepted at 12th International Symposium on Empirical Software
Engineering and Measurement (ESEM), 10 pages, 201
Strange Quark Matter Theory
Theoretical approaches to strange and other types of quark matter accounted
for at the SQM2003 Meeting are reviewed. They range from simple statistical
models through perturbative QCD supported mico-dynamical simulations til
lattice gauge theory and astrophysics results. Finally some ideas for future
research in this field are outlined.Comment: Theory summary talk given at Strange Quark Matter 2003 Conference,
March 12-17, 2003, Atlantic Beach, NC, USA. (LateX 19 pages, 15 postscript
figures.
Instructor perspectives on iteration during upper-division optics lab activities
Although developing proficiency with modeling is a nationally endorsed
learning outcome for upper-division undergraduate physics lab courses, no
corresponding research-based assessments exist. Our longterm goal is to develop
assessments of students' modeling ability that are relevant across multiple
upper-division lab contexts. To this end, we interviewed 19 instructors from 16
institutions about optics lab activities that incorporate photodiodes.
Interviews focused on how those activities were designed to engage students in
some aspects of modeling. We find that, according to many interviewees,
iteration is an important aspect of modeling. In addition, interviewees
described four distinct types of iteration: revising apparatuses, revising
models, revising data-taking procedures, and repeating data collection using
existing apparatuses and procedures. We provide examples of each type of
iteration, and discuss implications for the development of future modeling
assessments.Comment: 4 pages, 1 figure; under revie
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