13,408 research outputs found
Discovery of Eight z ~ 6 Quasars in the Sloan Digital Sky Survey Overlap Regions
We present the discovery of eight quasars at z~6 identified in the Sloan
Digital Sky Survey (SDSS) overlap regions. Individual SDSS imaging runs have
some overlap with each other, leading to repeat observations over an area
spanning >4000 deg^2 (more than 1/4 of the total footprint). These overlap
regions provide a unique dataset that allows us to select high-redshift quasars
more than 0.5 mag fainter in the z band than those found with the SDSS
single-epoch data. Our quasar candidates were first selected as i-band dropout
objects in the SDSS imaging database. We then carried out a series of follow-up
observations in the optical and near-IR to improve photometry, remove
contaminants, and identify quasars. The eight quasars reported here were
discovered in a pilot study utilizing the overlap regions at high galactic
latitude (|b|>30 deg). These quasars span a redshift range of 5.86<z<6.06 and a
flux range of 19.3<z_AB<20.6 mag. Five of them are fainter than z_AB=20 mag,
the typical magnitude limit of z~6 quasars used for the SDSS single-epoch
images. In addition, we recover eight previously known quasars at z~6 that are
located in the overlap regions. These results validate our procedure for
selecting quasar candidates from the overlap regions and confirming them with
follow-up observations, and provide guidance to a future systematic survey over
all SDSS imaging regions with repeat observations.Comment: AJ in press (8 pages
Evolution of a Web-Scale Near Duplicate Image Detection System
Detecting near duplicate images is fundamental to the content ecosystem of
photo sharing web applications. However, such a task is challenging when
involving a web-scale image corpus containing billions of images. In this
paper, we present an efficient system for detecting near duplicate images
across 8 billion images. Our system consists of three stages: candidate
generation, candidate selection, and clustering. We also demonstrate that this
system can be used to greatly improve the quality of recommendations and search
results across a number of real-world applications.
In addition, we include the evolution of the system over the course of six
years, bringing out experiences and lessons on how new systems are designed to
accommodate organic content growth as well as the latest technology. Finally,
we are releasing a human-labeled dataset of ~53,000 pairs of images introduced
in this paper
Visual Search at eBay
In this paper, we propose a novel end-to-end approach for scalable visual
search infrastructure. We discuss the challenges we faced for a massive
volatile inventory like at eBay and present our solution to overcome those. We
harness the availability of large image collection of eBay listings and
state-of-the-art deep learning techniques to perform visual search at scale.
Supervised approach for optimized search limited to top predicted categories
and also for compact binary signature are key to scale up without compromising
accuracy and precision. Both use a common deep neural network requiring only a
single forward inference. The system architecture is presented with in-depth
discussions of its basic components and optimizations for a trade-off between
search relevance and latency. This solution is currently deployed in a
distributed cloud infrastructure and fuels visual search in eBay ShopBot and
Close5. We show benchmark on ImageNet dataset on which our approach is faster
and more accurate than several unsupervised baselines. We share our learnings
with the hope that visual search becomes a first class citizen for all large
scale search engines rather than an afterthought.Comment: To appear in 23rd SIGKDD Conference on Knowledge Discovery and Data
Mining (KDD), 2017. A demonstration video can be found at
https://youtu.be/iYtjs32vh4
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