120,929 research outputs found
A Study on Agreement in PICO Span Annotations
In evidence-based medicine, relevance of medical literature is determined by
predefined relevance conditions. The conditions are defined based on PICO
elements, namely, Patient, Intervention, Comparator, and Outcome. Hence, PICO
annotations in medical literature are essential for automatic relevant document
filtering. However, defining boundaries of text spans for PICO elements is not
straightforward. In this paper, we study the agreement of PICO annotations made
by multiple human annotators, including both experts and non-experts.
Agreements are estimated by a standard span agreement (i.e., matching both
labels and boundaries of text spans), and two types of relaxed span agreement
(i.e., matching labels without guaranteeing matching boundaries of spans).
Based on the analysis, we report two observations: (i) Boundaries of PICO span
annotations by individual human annotators are very diverse. (ii) Despite the
disagreement in span boundaries, general areas of the span annotations are
broadly agreed by annotators. Our results suggest that applying a standard
agreement alone may undermine the agreement of PICO spans, and adopting both a
standard and a relaxed agreements is more suitable for PICO span evaluation.Comment: Accepted in SIGIR 2019 (Short paper
Photoinjector-generation of a flat electron beam with transverse emittance ratio of 100
The generation of a flat electron beam directly from a photoinjector is an
attractive alternative to the electron damping ring as envisioned for linear
colliders. It also has potential applications to light sources such as the
generation of ultra-short x-ray pulses or Smith-Purcell free electron lasers.
In this Letter, we report on the experimental generation of a flat-beam with a
measured transverse emittance ratio of for a bunch charge of
nC; the smaller measured normalized root-mean-square emittance is
m and is limited by the resolution of our experimental setup.
The experimental data, obtained at the Fermilab/NICADD Photoinjector
Laboratory, are compared with numerical simulations and the expected scaling
laws.Comment: 5 pages, 3 figure
Detecting structural breaks in seasonal time series by regularized optimization
Real-world systems are often complex, dynamic, and nonlinear. Understanding
the dynamics of a system from its observed time series is key to the prediction
and control of the system's behavior. While most existing techniques tacitly
assume some form of stationarity or continuity, abrupt changes, which are often
due to external disturbances or sudden changes in the intrinsic dynamics, are
common in time series. Structural breaks, which are time points at which the
statistical patterns of a time series change, pose considerable challenges to
data analysis. Without identification of such break points, the same dynamic
rule would be applied to the whole period of observation, whereas false
identification of structural breaks may lead to overfitting. In this paper, we
cast the problem of decomposing a time series into its trend and seasonal
components as an optimization problem. This problem is ill-posed due to the
arbitrariness in the number of parameters. To overcome this difficulty, we
propose the addition of a penalty function (i.e., a regularization term) that
accounts for the number of parameters. Our approach simultaneously identifies
seasonality and trend without the need of iterations, and allows the reliable
detection of structural breaks. The method is applied to recorded data on fish
populations and sea surface temperature, where it detects structural breaks
that would have been neglected otherwise. This suggests that our method can
lead to a general approach for the monitoring, prediction, and prevention of
structural changes in real systems.Comment: Safety, Reliability, Risk and Life-Cycle Performance of Structures
and Infrastructures (Edited by George Deodatis, Bruce R. Ellingwood and Dan
M. Frangopol), CRC Press 2014, Pages 3621-362
An quantum approach of measurement based on the Zurek's triple model
In a close form without referring the time-dependent Hamiltonian to the total
system, a consistent approach for quantum measurement is proposed based on
Zurek's triple model of quantum decoherence [W.Zurek, Phys. Rev. D 24, 1516
(1981)]. An exactly-solvable model based on the intracavity system is dealt
with in details to demonstrate the central idea in our approach: by peeling off
one collective variable of the measuring apparatus from its many degrees of
freedom, as the pointer of the apparatus, the collective variable de-couples
with the internal environment formed by the effective internal variables, but
still interacts with the measured system to form a triple entanglement among
the measured system, the pointer and the internal environment. As another
mechanism to cause decoherence, the uncertainty of relative phase and its
many-particle amplification can be summed up to an ideal entanglement or an
Shmidt decomposition with respect to the preferred basis.Comment: 22pages,3figure
Efficient Construction of Probabilistic Tree Embeddings
In this paper we describe an algorithm that embeds a graph metric
on an undirected weighted graph into a distribution of tree metrics
such that for every pair , and
. Such embeddings have
proved highly useful in designing fast approximation algorithms, as many hard
problems on graphs are easy to solve on tree instances. For a graph with
vertices and edges, our algorithm runs in time with high
probability, which improves the previous upper bound of shown by
Mendel et al.\,in 2009.
The key component of our algorithm is a new approximate single-source
shortest-path algorithm, which implements the priority queue with a new data
structure, the "bucket-tree structure". The algorithm has three properties: it
only requires linear time in the number of edges in the input graph; the
computed distances have a distance preserving property; and when computing the
shortest-paths to the -nearest vertices from the source, it only requires to
visit these vertices and their edge lists. These properties are essential to
guarantee the correctness and the stated time bound.
Using this shortest-path algorithm, we show how to generate an intermediate
structure, the approximate dominance sequences of the input graph, in time, and further propose a simple yet efficient algorithm to converted
this sequence to a tree embedding in time, both with high
probability. Combining the three subroutines gives the stated time bound of the
algorithm.
Then we show that this efficient construction can facilitate some
applications. We proved that FRT trees (the generated tree embedding) are
Ramsey partitions with asymptotically tight bound, so the construction of a
series of distance oracles can be accelerated
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