bluuebunny/crossref_metadata_2025_split huggingface dataset:
First Results from the Rapid-response Spectrophotometric Characterization of Near-Earth Objects Using RATIR
Authors: Navarro-Meza S. , Mommert M. , Trilling D. E. , Butler N. , Reyes-Ruiz M. , Pichardo B. , Axelrod T. , Jedicke R. , Moskovitz N. 
Published: April 2019

Abstract
As part of our multi-observatory, multifilter campaign, we present r–i color observations of 82 near-Earth objects (NEOs) obtained with the reionization and transients infrared camera (RATIR) instrument on the 1.5 m robotic telescope at the San Pedro Martir’s National Observatory in Mexico. Our project is particularly focused on rapid-response observations of small (≲850 m) NEOs. The rapid response and the use of spectrophotometry allows us to constrain the taxonomic classification of NEOs with high efficiency. Here we present the methodology of our observations and our result, suggesting that the ratio of C-type to S-type asteroids in a size range of ∼30–850 m is 1.1, which is in accordance with our previous results. We also find that 10% of all NEOs in our sample are neither C- nor S-type asteroids
Buried Black Hole Growth in IR-selected Mergers: New Results from Chandra
Authors: Pfeifle Ryan W. , Satyapal Shobita , Secrest Nathan J. , Gliozzi Mario , Ricci Claudio , Ellison Sara L. , Rothberg Barry , Cann Jenna , Blecha Laura , Williams James K. , Constantin Anca 
Published: April 2019

Abstract
Observations and theoretical simulations suggest that a significant fraction of merger-triggered accretion onto supermassive black holes is highly obscured, particularly in late-stage galaxy mergers, when the black hole is expected to grow most rapidly. Starting with the Wide-Field Infrared Survey Explorer all-sky survey, we identified a population of galaxies whose morphologies suggest ongoing interaction and which exhibit red mid-infrared colors often associated with powerful active galactic nuclei (AGNs). In a follow-up to our pilot study, we now present Chandra/ACIS and XMM-Newton X-ray observations for the full sample of the brightest 15 IR-preselected mergers. All mergers reveal at least one nuclear X-ray source, with 8 out of 15 systems exhibiting dual nuclear X-ray sources, highly suggestive of single and dual AGNs. Combining these X-ray results with optical line ratios and with near-IR coronal emission line diagnostics, obtained with the near-IR spectrographs on the Large Binocular Telescope, we confirm that 13 out of the 15 mergers host AGNs, two of which host dual AGNs. Several of these AGNs are not detected in the optical. All X-ray sources appear X-ray weak relative to their mid-infrared continuum, and of the nine X-ray sources with sufficient counts for spectral analysis, eight reveal strong evidence of high absorption with column densities of N
H ≳ 1023 cm−2. These observations demonstrate that a significant population of single and dual AGNs are missed by optical studies, due to high absorption, adding to the growing body of evidence that the epoch of peak black hole growth in mergers occurs in a highly obscured phase.
Focused Transport of Solar Energetic Particles in Interplanetary Space and the Formation of the Anisotropic Beam-like Distribution of Particles in the Onset Phase of Large Gradual Events
Authors: Li Gen , Lee Martin A. 
Published: April 2019

Abstract
In the onset phase of large gradual solar energetic particle (SEP) events, the first particles of a given rigidity to arrive at Earth are accelerated in the low corona, focused into a narrow cone of pitch angles by the diverging magnetic field, and transported from near the Sun to 1 au with minimal scattering. The effects of focused transport on the evolution of the beam-like SEPs are investigated analytically. The model assumes for simplicity a constant focusing length and a constant pitch-angle diffusion coefficient for SEPs at small pitch angles. Cross-field transport is ignored. This analytical approximation provides a reasonable representation of the spatial and pitch-angle distribution of the beam-like SEPs. Assuming an instantaneous injection of SEPs near the Sun, the model naturally reproduces several features of the SEP onset profiles observed at 1 au, including a spike-like time–intensity profile with rapid rising and declining edges that resemble a Reid–Axford profile. By assuming an extended injection profile with the shape of an isosceles triangle, we fit the onset phase data of the 2005 January 20 GLE event to our model. The derived mean free path (∼4 au) for relativistic protons is much larger than the theoretical prediction based on the standard quasilinear theory but consistent with our assumption of nearly scatter-free transport and can be explained by a reduced scattering rate, due to particles interacting with ambient turbulence with a Goldreich–Sridhar spectrum. Assuming that the SEPs that are scattered out of the beam are governed by spatial diffusive transport in interplanetary space, we perform an illustrative calculation to account for the nearly isotropic phase following the anisotropic onset as a natural result of the interplanetary transport of SEPs.
A High-performance and Portable All-Mach Regime Flow Solver Code with Well-balanced Gravity. Application to Compressible Convection
Authors: Padioleau Thomas , Tremblin Pascal , Audit Edouard , Kestener Pierre , Kokh Samuel 
Published: April 2019

Abstract
Convection is an important physical process in astrophysics well-studied using numerical simulations under the Boussinesq and/or anelastic approximations. However, these approaches reach their limits when compressible effects are important in the high-Mach flow regime, e.g., in stellar atmospheres or in the presence of accretion shocks. In order to tackle these issues, we propose a new high-performance and portable code called “ARK” with a numerical solver well suited for the stratified compressible Navier–Stokes equations. We take a finite-volume approach with machine precision conservation of mass, transverse momentum, and total energy. Based on previous works in applied mathematics, we propose the use of a low-Mach correction to achieve a good precision in both low and high-Mach regimes. The gravity source term is discretized using a well-balanced scheme in order to reach machine precision hydrostatic balance. This new solver is implemented using the Kokkos library in order to achieve high-performance computing and portability across different architectures (e.g., multi-core, many-core, and GP-GPU). We show that the low-Mach correction allows to reach the low-Mach regime with a much better accuracy than a standard Godunov-type approach. The combined well-balanced property and the low-Mach correction allowed us to trigger Rayleigh–Bénard convective modes close to the critical Rayleigh number. Furthermore, we present 3D turbulent Rayleigh–Bénard convection with low diffusion using the low-Mach correction leading to a higher kinetic energy power spectrum. These results are very promising for future studies of high Mach and highly stratified convective problems in astrophysics.
RR Lyrae Stars in the Field of Sagittarius II
Authors: Joo Seok-Joo , Kyeong Jaemann , Yang Soung-Chul , Han Sang-Il , Sung Eon-Chang , Rey Soo-Chang , Jerjen Helmut , Kim Hak-Sub , Kim Dongwon , Jeong Hyunjin , Ree Chang H. , Cha Sang-Mok , Lee Yongseok 
Published: April 2019

Abstract
We present the detection of RR Lyrae variable stars in the field of the Sagittarius II (Sgr II) ultra-faint dwarf (UFD) galaxy. Using B, V time-series photometry obtained with the Korea Microlensing Telescope Network (KMTNet) 1.6 m telescope at CTIO and G-band data from Gaia Data Release 2 (DR2), we identified and characterized two ab-type and four c-type RR Lyrae variables. Five out of the six stars are clustered within three half-light radii (∼4.′8) of the galaxy indicating their association with Sgr II, while the RRab star V4 is located ∼22′ from the galaxy center. By excluding V4, the high c-type fraction (0.8) and the period of the only RRab star V3 (P

V3 ≃ 0.666 days) suggest an Oosterhoff II (Oo II) classification for Sgr II. Located close to the locus of Oo II clusters in the period–amplitude diagram, V3 is similar to RRab stars in other UFDs having Oosterhoff-intermediate and Oo II properties. Sgr II is, however, more compact than usual UFDs, placed in between star clusters and dwarf galaxies in the size–luminosity plane, and therefore spectroscopic studies are eventually required to ascertain the true nature of this stellar system. We derive the metallicity ([Fe/H]RRab ≃ −2.1 ± 0.3) and heliocentric distance (∼64 ± 3 kpc) of Sgr II from the RR Lyrae stars, and estimate its age (∼12 Gyr) based on our stellar population models. The Oosterhoff properties of UFDs can be explained with the evolution effect of RR Lyrae stars in the instability strip.
Le « prêt payant ». Les paradoxes de l’économie collaborative
Authors: Jacquet Édouard 
Published: April 2019

Depuis 2011, le mouvement de l’« économie collaborative » gagne en popularité. Les entreprises issues de ce mouvement proposent à leurs utilisateurs un cadre d’interaction ambigu porté par un double discours mêlant à la fois registre marchand et désintéressement. À travers l’exemple d’Airbnb, site via lequel plus de 25 millions de particuliers ont loué un appartement, cet article décrit le travail des utilisateurs pour maintenir cette délicate définition de la situation que requiert l’hospitalité marchande. L’analyse proposée est fondée sur des entretiens menés auprès d’« hôtes » Airbnb et mobilise le cadre goffmanien pour expliquer leur travail relationnel.
Les refrains de la mondialisation
Authors: Da Lage Émilie , Debruyne François 
Published: April 2019

Cette contribution vise à interroger l’évolution des travaux de l’économie politique de la communication et des cultural studies sous le thème : musique et mondialisation. Celui-ci oblige souvent les chercheurs à réviser certaines routines conceptuelles ; il permet de voir travailler dans le détail des perspectives, des méthodes, des positionnements critiques, des déplacements et des évolutions, voire d’éclairer des arrière-plans plus transversaux. C’est ainsi que, contre toute attente de réconciliation, ces deux traditions critiques apparaissent d’abord comme incommensurables et, finalement, plus dissemblables et incompatibles qu’elles ne l’ont peut-être jamais été. Mais cet article est aussi l’occasion de rendre visibles des points de fuite, des consonances et des dissonances, par-delà les termes des débats entre les deux courants.
Internet, une société contre l’État ?
Authors: Loveluck Benjamin 
Published: April 2019

L’informatique en réseau a souvent été présentée comme un instrument favorisant l’auto-organisation de la société civile, à partir de modes alternatifs de distribution du pouvoir et de coordination des activités. L’histoire d’internet, abordée du point de vue de l’histoire des idées, montre que de telles propriétés ont donné lieu à la formation d’une véritable philosophie politique que nous avons appelée le libéralisme informationnel . Celle-ci a vu différents modèles d’économie politique s’affronter ; nous en présentons ici le mouvement général ainsi que les divergences internes. Nous terminons par un exposé de trois grandes formes de gouvernementalité qui en sont issues, et qui ouvrent à une critique de l’économie politique en régime numérique : la captation, la dissémination et l’auto-institution.
Presse en ligne et communautés cognitives
Authors: Carbou Guillaume 
Published: April 2019

Cet article entend montrer que les sections commentaires de certains sites d’actualité contribuent à stabiliser des communautés à la forte homogénéité idéologique. Après avoir circonscrit une définition de la « communauté cognitive » comme lieu de construction d’une unité d’appréhension du monde dans l’interaction discursive, nous montrons que les agoras numériques que fournissent les sites d’information en ligne permettent aux internautes de tester, confronter, et renforcer une unité idéologique. Nous appuyons notre propos par une analyse argumentative d’un corpus de commentaires sur les sites Atlantico.fr et l’Humanité.fr en réaction à l’« affaire DSK ». Nous défendons ainsi l’intérêt de l’analyse qualitative des tableaux de commentaires pour observer avec finesse des sédimentations idéologiques sur le web.
Les algorithmes de recommandation musicale et l’autonomie de l’auditeur
Authors: Beuscart Jean-Samuel , Coavoux Samuel , Maillard Sisley 
Published: April 2019

Les services d’écoute musicale en streaming se situent à mi-chemin entre deux dispositifs antérieurs, la radio et la collection de disques, et deux modes d’agentivité associés : le consommateur pris en charge par la programmation musicale dans le cas de la radio, l’amateur dans le cas de la collection. Ils proposent ainsi un régime hybride de prise en charge personnalisée, adaptée aux goûts des usagers, mesurés par leurs écoutes passées, via l’usage de systèmes de recommandation. Dans quelle mesure la figure dessinée par les interfaces se traduit-elle dans les comportements réels des auditeurs ? Nous nous appuyons sur l’analyse des traces d’activités musicales d’un échantillon aléatoire de 4000 utilisateurs d’une plateforme musicale, suivi pendant une période de cinq mois, pour répondre à cette question. Nous décrivons d’abord la distribution des écoutes, et montrons que si la diversité des consommations sur la plateforme est plus grande que sur d’autres dispositifs, les écoutes demeurent fortement concentrées sur les artistes les plus populaires. Nous examinons ensuite les usages des recommandations par les usagers, en montrant qu’ils restent mesurés, inégalement distribués, et que les usages de découverte musicale, s’ils orientent les usagers vers des musiques de la mid-tail et de la long-tail, demeurent marginaux.
L’économie de la découverte musicale à l’ère numérique
Authors: Maisonneuve Sophie 
Published: April 2019

Prenant acte des mutations survenues dans l’économie de la production et de la distribution de la musique avec la « révolution numérique » et de ses implications en termes de consommation, cet article en analyse les effets sur la manière dont les amateurs découvrent de nouvelles musiques : quelle est la place des dispositifs commerciaux, et notamment des algorithmes de recommandation ? La « numérimorphose » des pratiques de consommation musicale est-elle complète à cet égard ? Les « digital natives », en particulier, sont-ils entièrement convertis au régime numérique ? À partir d’une enquête portant sur une trentaine d’entretiens semi-directifs approfondis réalisés auprès de jeunes de 17 à 34 ans, cet article s’efforce de répondre à ces questions.
L’État plateforme et l’identification numérique des usagers
Authors: Alauzen Marie 
Published: April 2019

L’article interroge la notion d’État plateforme qui a guidé l’activité coordonnée de réforme de l’État français, entreprise entre 2014 et 2017, au Secrétariat général pour la modernisation de l’action publique (SGMAP). S’appuyant sur une ethnographie approfondie des services du SGMAP, il montre comment l’État plateforme a pris forme dans une application d’identification et d’échange de données administratives du nom de FranceConnect. Du choix des protocoles, à la conformité au droit ou à la formulation de l’identité, la conception administrative et informatique de l’application a engagé différentes épreuves techniques, politiques et juridiques. Nous verrons comment, dans ces épreuves, se sont façonnées deux caractéristiques de l’État en prise avec les technologies informatiques : la souveraineté numérique et l’ergonomie des services publics.
Emerging Technologies in the Search for the Submerged Cultural Landscapes of the Pacific Continental Shelf
Authors: Gusick Amy E , Maloney Jillian , King Roslynn B , Braje Todd J 
Published: April 2019

Abstract
As applications for offshore renewable energy projects increase, state and federal land managers have become concerned over potential impacts to cultural heritage resources along submerged landscapes. Identification, documentation, and management of historical shipwrecks have been relatively common, but methods for identifying submerged pre-contact archaeological deposits are developing in many coastal regions of the continental United States. Permitting agencies in certain regions along the Gulf of Mexico and the Atlantic Ocean typically require management plans that include mitigation measures for submerged archaeological sites. Over the last decade, resource managers along Pacific Coast regions have become increasingly aware of the need for submerged archaeological site protection. This is especially important since the eastern Pacific continental shelf has become a focal point in the search for late Pleistocene migrations into the Americas and other evidence of pre-contact habitation in coastal regions since the Last Glacial Maximum (LGM). Integral to this search is the identification of submerged Pleistocene landforms that may favor preservation of pre-contact archaeological sites.
Stemming from this, our multidisciplinary and multi-institutional effort includes marine geologists, marine biologists, and archaeologists synthesizing existing data using GIS models, and collecting new side scan sonar, CHIRP, and multibeam bathymetry data ground truthed with marine sediment cores. This methodology for the identification of submerged archaeological deposits is not new; however, the landscape approach that defines our research, and our focus on understanding paleolandscapes using modeling, sonar survey, and marine coring is the first of its kind on the eastern Pacific continental shelf.
The goal of our project is to develop an archaeological sensitivity model, which the Bureau of Ocean Energy Management can consult in the offshore energy permitting process. As such, we are building our model using data from California’s Northern Channel Islands and testing the model along Oregon’s central coast. Results suggest that with the right technologies, sensitive landscape features such as paleochannels, paleoestuaries, and offshore tar seeps – all features used by Native American communities during the late Pleistocene and Holocene along the Pacific Coast – can be identified and used to model sensitive archaeological landscapes. We also are testing the efficacy of controlled-source marine electromagnetic methods in conjunction with sonar survey data for the identification of tar seeps, paleochannels, and buried archaeological shell midden deposits. This combined methodological approach is unique to North America’s Pacific Coast and represents a pioneering effort in the search for submerged archaeological deposits, which will help identify, document, and preserve underwater cultural heritage resources.
Study of the Annular Restriction Effect Caused by Magnetorheological Fluids in the Presence of a Magnetic Field
Authors: Estrada-Giraldo John , Nielsen Garrett , Akbari Babak 
Published: April 2019

Abstract
Magnetorheological fluids (MRF) have their rheology modified in the presence of a magnetic field. The MRF consist of a base fluid, magnetizable particles, and a viscosifier that supports these particles. The magnetizable particles align in the direction of the magnetic field, creating a barrier, and thus modifying the rheology of the mixture. When a large enough magnetic field is applied to the MRF, the fluid's yield stress increases drastically in a matter of milliseconds. Due to this fluid response, a tunable back-pressure can be generated when the MRF's rheology is modified downhole with the use of a permanent magnet assembly as part of the BHA. One potential application of this technology is to facilitate drilling operations in narrower mud windows. As an analogy, the technology proposed in this paper works under the same principle of the conventional MPD systems, but with the additional capability of being able to apply a backpressure downhole where the magnetic assembly is located, and therefore only modifying the pressure below the tool location. As a result, abnormally pressured formations could be safely drilled without fracturing the formations above, due to the pressure profile above the magnetic assembly remaining unchanged.
As a proposed way to demonstrate this principle, the shear stress variation at different magnetic field intensities is evaluated for different samples of MRF in a special rotating bob rheometer equipped with an electromagnet. A higher magnetic field applied to the MRF produces a higher shear stress, and thus a larger pressure-drop. Upscaling this effect, some of these MRF samples were circulated in a large-scale flow-loop with two concentric pipes that resemble the drill pipe and the annulus. On the flow-loop, some electromagnets and permanent magnets were strategically located to apply a magnetic field to the circulating fluid. The pressure changes (back-pressure) along the system was monitored to evaluate the effect of the magnetorheological response on the pressure variation. As an additional application, a potential electromagnetic surface choke that "activates" the MRF could create a flow restriction, and therefore a back pressure. In that sense, this electromagnetic choke could provide a finer aperture of the choke when the magnetic field is modified accordingly and could be less susceptible to erosion of mechanical parts from solids contained in the mud.
Advances in Chemical EOR Technologies: New Development in Field-Scale Chemical Flooding Simulation
Authors: R. B. Fernandes Bruno , A. Pope Gary , Sepehrnoori Kamy , R. Lashgari Hamid 
Published: April 2019

Abstract
The accurate and efficient large-scale simulation of chemical flooding using mechanistic reservoir simulation models has been a big challenge for the past several decades, but recent advances in both the modelling of physical properties and numerical algorithms have finally made it possible to use mechanistic chemical simulators for field-scale application. In this paper, a new version of UTCHEM built in an adaptive implicit framework was used to simulate chemical floods in large heterogeneous oil reservoirs. The new developments made it feasible to do simulations using several million gridblocks with sufficiently small gridblock sizes to ensure physical accuracy. Four case studies of polymer flooding and surfactant-polymer flooding are presented. The grid sizes range from 800,000 to 3.7 million gridblocks. The incremental enhanced oil recovery is illustrated by comparison with waterflooding. The polymer model takes into account the effects of shear thinning, adsorption, and salinity among other phenomena. The surfactant model takes into account all Winsor microemulsion phase behavior types, salinity effects, and capillary desaturation among other process phenomena. The surfactant-polymer floods are designed with a salinity gradient.