9,403 research outputs found
Finding Patterns in a Knowledge Base using Keywords to Compose Table Answers
We aim to provide table answers to keyword queries against knowledge bases.
For queries referring to multiple entities, like "Washington cities population"
and "Mel Gibson movies", it is better to represent each relevant answer as a
table which aggregates a set of entities or entity-joins within the same table
scheme or pattern. In this paper, we study how to find highly relevant patterns
in a knowledge base for user-given keyword queries to compose table answers. A
knowledge base can be modeled as a directed graph called knowledge graph, where
nodes represent entities in the knowledge base and edges represent the
relationships among them. Each node/edge is labeled with type and text. A
pattern is an aggregation of subtrees which contain all keywords in the texts
and have the same structure and types on node/edges. We propose efficient
algorithms to find patterns that are relevant to the query for a class of
scoring functions. We show the hardness of the problem in theory, and propose
path-based indexes that are affordable in memory. Two query-processing
algorithms are proposed: one is fast in practice for small queries (with small
patterns as answers) by utilizing the indexes; and the other one is better in
theory, with running time linear in the sizes of indexes and answers, which can
handle large queries better. We also conduct extensive experimental study to
compare our approaches with a naive adaption of known techniques.Comment: VLDB 201
Authentic Learning Design Failures: The Need for Learner and Contextual Analysis and Participatory Design
This design case examines what program leaders learned from failures in the design of a program of authentic learning about teaching diverse audiences through educational outreach. The program was initiated and then redesigned to develop the teaching and communication skills of graduate students from a wide range of backgrounds by engaging them in authentic experiences with middle school teachers and students. Analysis of post-program data revealed seven design failures related to the lack of upfront analysis to inform the program design. Each design failure was detailed through a fishbone diagram method to identify the corre- sponding contributing factors. The failures in this design case reinforce the need for upfront learner analysis and contextual analysis. A participatory design was also suggested from the post-program data analysis. An instructional design model was recommended for continuous program redesign
Network Inference via the Time-Varying Graphical Lasso
Many important problems can be modeled as a system of interconnected
entities, where each entity is recording time-dependent observations or
measurements. In order to spot trends, detect anomalies, and interpret the
temporal dynamics of such data, it is essential to understand the relationships
between the different entities and how these relationships evolve over time. In
this paper, we introduce the time-varying graphical lasso (TVGL), a method of
inferring time-varying networks from raw time series data. We cast the problem
in terms of estimating a sparse time-varying inverse covariance matrix, which
reveals a dynamic network of interdependencies between the entities. Since
dynamic network inference is a computationally expensive task, we derive a
scalable message-passing algorithm based on the Alternating Direction Method of
Multipliers (ADMM) to solve this problem in an efficient way. We also discuss
several extensions, including a streaming algorithm to update the model and
incorporate new observations in real time. Finally, we evaluate our TVGL
algorithm on both real and synthetic datasets, obtaining interpretable results
and outperforming state-of-the-art baselines in terms of both accuracy and
scalability
A radio structure resolved at the deca-parsec scale in radio-quiet quasar PDS 456 with an extremely powerful X-ray outflow
Active galactic nuclei (AGN) accreting at rates close to the Eddington limit
can host radiatively driven mildly relativistic outflows. Some of these X-ray
absorbing but powerful outflows may produce strong shocks resulting in a
significant non-thermal emission. This outflow-driven radio emission may be
detectable in the radio-quiet quasar PDS 456 since it has a bolometric
luminosity reaching the Eddington limit and a relativistic wide-aperture X-ray
outflow with a kinetic power high enough to quench the star formation in its
host galaxy. To investigate this possibility, we performed very-long-baseline
interferometric (VLBI) observations of the quasar with the European VLBI
Network (EVN) at 5 GHz. The EVN image with the full resolution reveals two
faint and diffuse radio components with a projected separation of about 20 pc
and an average brightness temperature of around two million Kelvin. In relation
to the optical sub-mas-accuracy position measured by the Gaia mission, the two
components are very likely on opposite sides of an undetected radio core. The
VLBI structure at the deca-pc scale can thus be either a young jet or a
bidirectional radio-emitting outflow, launched in the vicinity of a strongly
accreting central engine. Two diffuse components at the hecto-pc scale, likely
the relic radio emission from the past AGN activity, are tentatively detected
on each side in the low-resolution EVN image.Comment: 6 pages, 2 figures, 1 table. Accepted for publication in MNRA
An optimal transport approach for the multiple quantile hedging problem
We consider the multiple quantile hedging problem, which is a class of
partial hedging problems containing as special examples the quantile hedging
problem (F{\"o}llmer \& Leukert 1999) and the PnL matching problem (introduced
in Bouchard \& Vu 2012). In complete non-linear markets, we show that the
problem can be reformulated as a kind of Monge optimal transport problem. Using
this observation, we introduce a Kantorovitch version of the problem and prove
that the value of both problems coincide. In the linear case, we thus obtain
that the multiple quantile hedging problem can be seen as a semi-discrete
optimal transport problem, for which we further introduce the dual problem. We
then prove that there is no duality gap, allowing us to design a numerical
method based on SGA algorithms to compute the multiple quantile hedging price
Imaging and variability studies of CTA~102 during the 2016 January -ray flare
The -ray bright blazar CTA 102 is studied using imaging (new 15 GHz
and archival 43 GHz Very Long Baseline Array, VLBA data) and time variable
optical flux density, polarization degree and electric vector position angle
(EVPA) spanning between 2015 June 1 and 2016 October 1, covering a prominent
-ray flare during 2016 January. The pc-scale jet indicates expansion
with oscillatory features upto 17 mas. Component proper motions are in the
range 0.04 - 0.33 mas/yr with acceleration upto 1.2 mas followed by a slowing
down beyond 1.5 mas. A jet bulk Lorentz factor 17.5, position angle of
128.3 degrees, inclination angle 6.6 degrees and intrinsic half opening
angle 1.8 degrees are derived from the VLBA data. These inferences are
employed in a helical jet model to infer long term variability in flux density,
polarization degree, EVPA and a rotation of the Stokes Q and U parameters. A
core distance of = 22.9 pc, and a magnetic field
strength at 1 pc and the core location of 1.57 G and 0.07 G respectively are
inferred using the core shift method. The study is useful in the context of
estimating jet parameters and in offering clues to distinguish mechanisms
responsible for variability over different timescales.Comment: 20 pages, 7 figures, 3 tables; accepted for publication in Ap
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