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1. Shape From Sky: Polarimetric Normal Recovery Under the Sky

   Ichikawa, T. (June 2021, IEEE Conference on Computer Vision and Pattern Recognition)

   null (Ed.)

   The sky exhibits a unique spatial polarization pattern by scattering the unpolarized sun light. Just like insects use this unique angular pattern to navigate, we use it to map pixels to directions on the sky. That is, we show that the unique polarization pattern encoded in the polarimetric appearance of an object captured under the sky can be decoded to reveal the surface normal at each pixel. We derive a polarimetric reflection model of a diffuse plus mirror surface lit by the sun and a clear sky. This model is used to recover the per-pixel surface normal of an object from a single polarimetric image or from multiple polarimetric images captured under the sky at different times of the day. We experimentally evaluate the accuracy of our shape-from-sky method on a number of real objects of different surface compositions. The results clearly show that this passive approach to fine-geometry recovery that fully leverages the unique illumination made by nature is a viable option for 3D sensing. With the advent of quad-Bayer polarization chips, we believe the implications of our method span a wide range of domains. 

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2. Seeing the Night Sky

   https://doi.org/10.5194/ica-proc-2-33-2019  

   Flynn, Colin G.; Rice, Matthew T. (January 2019, Proceedings of the ICA)

   Abstract. Clear, dark night skies are harder to see now than ever before, and it will only become more difficult as people continue to move into heavily light polluted and expanding urban areas. Dark Sky Parks offer a place where anyone can go to experience true dark skies, observing the stars and other celestial bodies in conditions unencumbered by artificial light and other sources of pollution. An atlas of these Dark Sky Parks will raise awareness about their existence and locations with the goal of education and outreach. Observatories may be utilized with a similar outcome; however, they need to be located in close proximity to large populations but far enough away to optimize dark skies. This research presents an approach for mapping Dark Sky Parks in the United States through the ongoing production of Seeing the Night Sky: An Atlas of Dark Sky Parks, and a related GIS location optimization model to identify potential observatory locations in a defined study area based on land availability, slope, presence of water/floodplain, proximity to populated places, light pollution, elevation, and transportation infrastructure. 

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3. Mapping SYK to the sky

   https://doi.org/10.1007/JHEP09(2022)047  

   Pasterski, Sabrina; Verlinde, Herman (September 2022, Journal of High Energy Physics)

   A bstract The infrared behavior of gravity in 4D asymptotically flat spacetime exhibits a rich set of symmetries. This has led to a proposed holographic duality between the gravitational $$ \mathcal{S} $$ S -matrix and a dual field theory living on the celestial sphere. Most of our current understanding of the dictionary relies on knowledge of the 4D bulk. As such, identifying intrinsic 2D models that capture the correct symmetries and soft dynamics of 4D gravity is an active area of interest. Here we propose that a 2D generalization of SYK provides an instructive toy model for the soft limit of the gravitational sector in 4D asymptotically flat spacetime. We find that the symmetries and soft dynamics of the 2D SYK model capture the salient features of the celestial theory: exhibiting chaotic dynamics, conformal invariance, and a w 1+ ∞ symmetry. The holographic map from 2D SYK operators to the 4D bulk employs the Penrose twistor transform. 

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4. The Peeping Eye in the Sky

   Yue, Qinggang; Li, Zupei; Gao, Chao; Yu, Wei; Fu, Xinwen; Zhao, Wei (December 2018, IEEE Global Communications Conference)

   In this paper, we investigate the threat of drones equipped with recording devices, which capture videos of individuals typing on their mobile devices and extract the touch input such as passcodes from the videos. Deploying this kind of attack from the air is significantly challenging because of camera vibration and movement caused by drone dynamics and the wind. Our algorithms can estimate the motion trajectory of the touching finger, and derive the typing pattern and then touch inputs. Our experiments show that we can achieve a high success rate against both tablets and smartphones with a DJI Phantom drone from a long distance. A 2.5" NEUTRON mini drone flies outside a window and also achieves a high success rate against tablets behind the window. To the best of our knowledge, we are the first to systematically study drones revealing user inputs on mobile devices and use the finger motion trajectory alone to recover passcodes typed on mobile devices. 

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5. A Quick Look at the 3 GHz Radio Sky. II. Hunting for DRAGNs in the VLA Sky Survey

   https://doi.org/10.3847/1538-4365/acda30  

   Gordon, Yjan A.; Rudnick, Lawrence; Andernach, Heinz; Morabito, Leah K.; O’Dea, Christopher P.; Achong, Kaylan-Marie; Baum, Stefi A.; Bayona-Figueroa, Caryelis; Hooper, Eric J.; Mingo, Beatriz; et al (August 2023, The Astrophysical Journal Supplement Series)

   Abstract Active galactic nuclei (AGNs) can often be identified in radio images as two lobes, sometimes connected to a core by a radio jet. This multicomponent morphology unfortunately creates difficulties for source finders, leading to components that are (a) separate parts of a wider whole, and (b) offset from the multiwavelength cross identification of the host galaxy. In this work we define an algorithm, DRAGN hunter , for identifying double radio sources associated with AGNs (DRAGNs) from component catalog data in the first epoch Quick Look images of the high-resolution (≈3″ beam size) Very Large Array Sky Survey (VLASS). We use DRAGN hunter to construct a catalog of >17,000 DRAGNs in VLASS for which contamination from spurious sources is estimated at ≈11%. A “high-fidelity” sample consisting of 90% of our catalog is identified for which contamination is <3%. Host galaxies are found for ≈13,000 DRAGNs as well as for an additional 234,000 single-component radio sources. Using these data, we explore the properties of our DRAGNs, finding them to be typically consistent with Fanaroff–Riley class II sources and to allow us to report the discovery of 31 new giant radio galaxies identified using VLASS. 

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