79 research outputs found
Understanding Accretion Outbursts in Massive Protostars through Maser Imaging
The bright maser emission produced by several molecular species at centimeter
to long millimeter wavelengths provides an essential tool for understanding the
process of massive star formation. Unimpeded by the high dust optical depths
that affect shorter wavelength observations, the high brightness temperature of
these emission lines offers a way to resolve accretion and outflow motions down
to scales below 1 au in deeply embedded Galactic star-forming regions at
kiloparsec distances. The recent identification of extraordinary accretion
outbursts in two high-mass protostars, both of which were heralded by maser
flares, has rapidly impacted the traditional view of massive protostellar
evolution, leading to new hydrodynamic simulations that can produce such
episodic outbursts. In order to understand how these massive protostars evolve
in response to such events, larger, more sensitive ground-based centimeter
wavelength interferometers are needed that can simultaneously image multiple
maser species in the molecular gas along with faint continuum from the central
ionized gas. Fiducial observations of a large sample of massive protostars will
be essential in order to pinpoint the progenitors of future accretion
outbursts, and to quantify the outburst-induced changes in their protostellar
photospheres and outflow and accretion structures. Knowledge gained from these
studies will have broader impact on the general topic of accretion onto massive
objects.Comment: Science white paper submitted to the Astro2020 Decadal Survey. arXiv
admin note: substantial text overlap with arXiv:1806.0698
Automatic Discovery of Political Meme Genres with Diverse Appearances
Forms of human communication are not static -- we expect some evolution in
the way information is conveyed over time because of advances in technology.
One example of this phenomenon is the image-based meme, which has emerged as a
dominant form of political messaging in the past decade. While originally used
to spread jokes on social media, memes are now having an outsized impact on
public perception of world events. A significant challenge in automatic meme
analysis has been the development of a strategy to match memes from within a
single genre when the appearances of the images vary. Such variation is
especially common in memes exhibiting mimicry. For example, when voters perform
a common hand gesture to signal their support for a candidate. In this paper we
introduce a scalable automated visual recognition pipeline for discovering
political meme genres of diverse appearance. This pipeline can ingest meme
images from a social network, apply computer vision-based techniques to extract
local features and index new images into a database, and then organize the
memes into related genres. To validate this approach, we perform a large case
study on the 2019 Indonesian Presidential Election using a new dataset of over
two million images collected from Twitter and Instagram. Results show that this
approach can discover new meme genres with visually diverse images that share
common stylistic elements, paving the way forward for further work in semantic
analysis and content attribution.Comment: 13 pages, 14 figure
Spotting the difference: Context retrieval and analysis for improved forgery detection and localization
As image tampering becomes ever more sophisticated and commonplace, the need for image forensics algorithms that can accurately and quickly detect forgeries grows. In this paper, we revisit the ideas of image querying and retrieval to provide clues to better localize forgeries. We propose a method to perform large-scale image forensics on the order of one million images using the help of an image search algorithm and database to gather contextual clues as to where tampering may have taken place. In this vein, we introduce five new strongly invariant image comparison methods and test their effectiveness under heavy noise, rotation, and color space changes. Lastly, we show the effectiveness of these methods compared to passive image forensics using Nimble [1], a new, state-of-the-art dataset from the National Institute of Standards and Technology (NIST)
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