35,411 research outputs found
CSGNet: Neural Shape Parser for Constructive Solid Geometry
We present a neural architecture that takes as input a 2D or 3D shape and
outputs a program that generates the shape. The instructions in our program are
based on constructive solid geometry principles, i.e., a set of boolean
operations on shape primitives defined recursively. Bottom-up techniques for
this shape parsing task rely on primitive detection and are inherently slow
since the search space over possible primitive combinations is large. In
contrast, our model uses a recurrent neural network that parses the input shape
in a top-down manner, which is significantly faster and yields a compact and
easy-to-interpret sequence of modeling instructions. Our model is also more
effective as a shape detector compared to existing state-of-the-art detection
techniques. We finally demonstrate that our network can be trained on novel
datasets without ground-truth program annotations through policy gradient
techniques.Comment: Accepted at CVPR-201
The incorrect rotation curve of the Milky Way
In the fundamental quest of the rotation curve of the Milky Way, the
tangent-point (TP) method has long been the simplest way to infer velocities
for the inner, low latitude regions of the Galactic disk from observations of
the gas component. We test the validity of the method on realistic gas
distribution and kinematics of the Milky Way, using a numerical simulation of
the Galaxy. We show that the resulting velocity profile strongly deviates from
the true rotation curve of the simulation, as it overstimates it in the central
regions, and underestimates it around the bar corotation. Also, its shape
strongly depends on the orientation of the stellar bar. The discrepancies are
caused by highly non-uniform azimuthal velocities, and the systematic selection
by the TP method of high-velocity gas along the bar and spiral arms, or
low-velocity gas in less dense regions. The velocity profile is in good
agreement with the rotation curve only beyond corotation, far from massive
asymmetric structures. Therefore the observed velocity profile of the Milky Way
inferred by the TP method is expected to be very close to the true Galactic
rotation curve for 4.5<R<8 kpc. Another consequence is that the Galactic
velocity profile for R<4-4.5 kpc is very likely flawed by the non-uniform
azimuthal velocities, and does not represent the true Galactic rotation curve,
but instead local motions. The real shape of the innermost rotation curve is
probably shallower than previously thought. Using a wrong rotation curve has a
dramatic impact on the modelling of the mass distribution, in particular for
the bulge component of which derived enclosed mass within the central kpc and
scale radius are, respectively, twice and half of the actual values. We thus
strongly argue against using terminal velocities or the velocity curve from the
TP method for modelling the mass distribution of the Milky Way. (abridged)Comment: Accepted for publication in Astronomy & Astrophysics, 8 pages, 10
figures, revised version after A&A language editin
Multi-Content GAN for Few-Shot Font Style Transfer
In this work, we focus on the challenge of taking partial observations of
highly-stylized text and generalizing the observations to generate unobserved
glyphs in the ornamented typeface. To generate a set of multi-content images
following a consistent style from very few examples, we propose an end-to-end
stacked conditional GAN model considering content along channels and style
along network layers. Our proposed network transfers the style of given glyphs
to the contents of unseen ones, capturing highly stylized fonts found in the
real-world such as those on movie posters or infographics. We seek to transfer
both the typographic stylization (ex. serifs and ears) as well as the textual
stylization (ex. color gradients and effects.) We base our experiments on our
collected data set including 10,000 fonts with different styles and demonstrate
effective generalization from a very small number of observed glyphs
Search for Evergreens in Science: A Functional Data Analysis
Evergreens in science are papers that display a continual rise in annual
citations without decline, at least within a sufficiently long time period.
Aiming to better understand evergreens in particular and patterns of citation
trajectory in general, this paper develops a functional data analysis method to
cluster citation trajectories of a sample of 1699 research papers published in
1980 in the American Physical Society (APS) journals. We propose a functional
Poisson regression model for individual papers' citation trajectories, and fit
the model to the observed 30-year citations of individual papers by functional
principal component analysis and maximum likelihood estimation. Based on the
estimated paper-specific coefficients, we apply the K-means clustering
algorithm to cluster papers into different groups, for uncovering general types
of citation trajectories. The result demonstrates the existence of an evergreen
cluster of papers that do not exhibit any decline in annual citations over 30
years.Comment: 40 pages, 9 figure
Multiple Instance Learning: A Survey of Problem Characteristics and Applications
Multiple instance learning (MIL) is a form of weakly supervised learning
where training instances are arranged in sets, called bags, and a label is
provided for the entire bag. This formulation is gaining interest because it
naturally fits various problems and allows to leverage weakly labeled data.
Consequently, it has been used in diverse application fields such as computer
vision and document classification. However, learning from bags raises
important challenges that are unique to MIL. This paper provides a
comprehensive survey of the characteristics which define and differentiate the
types of MIL problems. Until now, these problem characteristics have not been
formally identified and described. As a result, the variations in performance
of MIL algorithms from one data set to another are difficult to explain. In
this paper, MIL problem characteristics are grouped into four broad categories:
the composition of the bags, the types of data distribution, the ambiguity of
instance labels, and the task to be performed. Methods specialized to address
each category are reviewed. Then, the extent to which these characteristics
manifest themselves in key MIL application areas are described. Finally,
experiments are conducted to compare the performance of 16 state-of-the-art MIL
methods on selected problem characteristics. This paper provides insight on how
the problem characteristics affect MIL algorithms, recommendations for future
benchmarking and promising avenues for research
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