732 research outputs found
Collective Sense-Making through the Twitter Service during the 2011 Egypt Revolution
This study explores the role of Twitter during the 2011 Egypt revolution. Drawing on the body of literatures on collective behavior in general and social movement in particular, we investigate the concept of sense-making which is considered as a key aspect of collective behavior. Our special focus will be placed on analyzing the changing patterns of hashtags by applying the Markov-Switching Model. The analysis of hashtags is expected to explicate (1) how the collective sense-making process emerges over time through Hashtags, and (2) what the implications of those sense-making processes are in the particular situation of the 2011 Egypt revolution. A few theoretical and practical implications will be discussed
Choice of Information: A Study of Twitter News Sharing during the 2009 Israel-Gaza Conflict
The study explores determinants of the prominence of public information sources in Twitter. Twitter users are conceptualized as the “gated” who play an active role in selecting and distributing news sources through their Twitter messages. Using Twitter data on the Israel-Gaza conflict, the study identifies three determinants that characterize information sources: whether they are produced by mainstream media, whether they are filtered through aggregator services, and the number of in-links to the source media generated by the online public
A Sociotechnical View of Information Diffusion and Social Changes: From Reprint to Retweet
This research in progress study explores the role of Twitter during the 2011 Egypt revolution. Drawing on a research method of historians who investigated the role of print technology during the Protestant Reformation in Western Europe during the early 16th century, we explicate the socio-technical implications of information diffusion through retweeting during radical social changes. Through retweet analysis, we identify inseparable dynamics of (1) existence of a few opinion leaders, (2) a large number of supporting individuals, and (3) the emergence of attendant collective sense-making process as a critical antecedent of radical social changes
Enabling a reliable STT-MRAM main memory simulation
STT-MRAM is a promising new memory technology with very desirable set of properties such as non-volatility, byte-addressability and high endurance. It has the potential to become the universal memory that could be incorporated to all levels of memory hierarchy. Although STT-MRAM technology got significant attention of various major memory manufacturers, to this day, academic research of STT-MRAM main memory remains marginal. This is mainly due to the unavailability of publicly available detailed timing parameters which are required to perform a cycle accurate main memory simulation. Our study presents a detailed analysis of STT-MRAM main memory timing and propose an approach to perform a reliable system level simulation of the memory technology. We seamlessly incorporate STT-MRAM timing parameters into DRAMSim2 memory simulator and use it as a part of the simulation infrastructure of the high-performance computing (HPC) systems. Our results suggests that, STT-MRAM main memory would provide performance comparable to DRAM, while opening up various opportunities for HPC system improvements. Most importantly, our study enables researchers to conduct reliable system level research on STT-MRAM main memory, and to explore the opportunities that this technology has to offer.This work was supported by BSC, Spanish Government through Programa Severo Ochoa (SEV-2015-0493), by the Spanish Ministry of Science and Technology through TIN2015-65316-P project and by the Generalitat de Catalunya (contracts 2014-SGR-1051 and 2014-SGR-1272).
This work has also received funding from the European Union's Horizon 2020 research and innovation programme under ExaNoDe project (grant agreement No 671578). The
authors wish to thank Terry Hulett, Duncan Bennett and Ben Cooke from Everspin Technologies Inc., for their technical support.Peer ReviewedPostprint (author's final draft
STT-MRAM for real-time embedded systems: performance and WCET implications
STT-MRAM is an emerging non-volatile memory quickly approaching DRAM in terms of capacity, frequency and device size. Intensified efforts in STT-MRAM research by the memory manufacturers may indicate a revolution with STT-MRAM memory technology is imminent, and therefore it is essential to perform system level research to explore use-cases and identify computing domains that could benefit from this technology. Special STT-MRAM features such as intrinsic radiation hardness, non-volatility, zero stand-by power and capability to function in extreme temperatures makes it particularly suitable for aerospace, avionics and automotive applications. Such applications often have real-time requirements --- that is, certain tasks must complete within a strict deadline. Analyzing whether this deadline is met requires Worst Case Execution Time (WCET) Analysis, which is a fundamental part of evaluating any real-time system. In this study, we investigate the feasibility of using STT-MRAM in real-time embedded systems by analyzing average system performance impact and WCET implications.This work was supported by BSC, Spanish Government through Programa Severo Ochoa (SEV-2015-0493), by the Spanish Ministry of Science and Technology through TIN2015-65316-P project and by the Generalitat de Catalunya (contracts 2014-SGR-1051 and 2014-SGR-1272). This work has also received funding from the European Union’s Horizon 2020 research and innovation programme under ExaNoDe project (grant agreement No 671578). Jaume Abella was partially supported by the Ministry of Economy and Competitive-ness under Ramon y Cajal postdoctoral fellowship RYC-2013-14717.Peer ReviewedPostprint (author's final draft
Vector meson production and nucleon resonance analysis in a coupled-channel approach for energies m_N < sqrt(s) < 2 GeV II: photon-induced results
We present a nucleon resonance analysis by simultaneously considering all
pion- and photon-induced experimental data on the final states gamma N, pi N, 2
pi N, eta N, K Lambda, K Sigma, and omega N for energies from the nucleon mass
up to sqrt(s) = 2 GeV. In this analysis we find strong evidence for the
resonances P_{31}(1750), P_{13}(1900), P_{33}(1920), and D_{13}(1950). The
omega N production mechanism is dominated by large P_{11}(1710) and
P_{13}(1900) contributions. In this second part we present the results on the
photoproduction reactions and the electromagnetic properties of the resonances.
The inclusion of all important final states up to sqrt(s) = 2 GeV allows for
estimates on the importance of the individual states for the GDH sum rule.Comment: 41 pages, 26 figures, discussion extended, typos corrected,
references updated, to appear in Phys. Rev.
On Effective Potential in Tortoise Coordinate
In this paper, we study the field dynamics in Tortoise coordinate where the
equation of motion of a scalar can be written as Schrodinger-like form. We
obtain a general form for effective potential by finding the Schrodinger
equation for scalar and spinor fields and study its global behavior in some
black hole backgrounds in three dimension such as BTZ black holes, new type
black holes and black holes with no horizon.
Especially, we study the asymptotic behavior of potential at infinity,
horizons and origin and find that its asymptotic in BTZ and new type solution
is completely different from that of vanishing horizon solution. In fact,
potential for vanishing horizon goes to a fixed quantity at infinity, while in
BTZ and new type black hole we have an infinite barrier.Comment: 18 pages, 9 figure
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb-Pb collisions at TeV
The elliptic, , triangular, , and quadrangular, , azimuthal
anisotropic flow coefficients are measured for unidentified charged particles,
pions and (anti-)protons in Pb-Pb collisions at TeV
with the ALICE detector at the Large Hadron Collider. Results obtained with the
event plane and four-particle cumulant methods are reported for the
pseudo-rapidity range at different collision centralities and as a
function of transverse momentum, , out to GeV/.
The observed non-zero elliptic and triangular flow depends only weakly on
transverse momentum for GeV/. The small dependence
of the difference between elliptic flow results obtained from the event plane
and four-particle cumulant methods suggests a common origin of flow
fluctuations up to GeV/. The magnitude of the (anti-)proton
elliptic and triangular flow is larger than that of pions out to at least
GeV/ indicating that the particle type dependence persists out
to high .Comment: 16 pages, 5 captioned figures, authors from page 11, published
version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/186
Centrality dependence of charged particle production at large transverse momentum in Pb-Pb collisions at TeV
The inclusive transverse momentum () distributions of primary
charged particles are measured in the pseudo-rapidity range as a
function of event centrality in Pb-Pb collisions at
TeV with ALICE at the LHC. The data are presented in the range
GeV/ for nine centrality intervals from 70-80% to 0-5%.
The Pb-Pb spectra are presented in terms of the nuclear modification factor
using a pp reference spectrum measured at the same collision
energy. We observe that the suppression of high- particles strongly
depends on event centrality. In central collisions (0-5%) the yield is most
suppressed with at -7 GeV/. Above
GeV/, there is a significant rise in the nuclear modification
factor, which reaches for GeV/. In
peripheral collisions (70-80%), the suppression is weaker with almost independently of . The measured nuclear
modification factors are compared to other measurements and model calculations.Comment: 17 pages, 4 captioned figures, 2 tables, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/284
Measurement of charm production at central rapidity in proton-proton collisions at TeV
The -differential production cross sections of the prompt (B
feed-down subtracted) charmed mesons D, D, and D in the rapidity
range , and for transverse momentum GeV/, were
measured in proton-proton collisions at TeV with the ALICE
detector at the Large Hadron Collider. The analysis exploited the hadronic
decays DK, DK, DD, and their charge conjugates, and was performed on a
nb event sample collected in 2011 with a
minimum-bias trigger. The total charm production cross section at TeV and at 7 TeV was evaluated by extrapolating to the full phase space
the -differential production cross sections at TeV
and our previous measurements at TeV. The results were compared
to existing measurements and to perturbative-QCD calculations. The fraction of
cdbar D mesons produced in a vector state was also determined.Comment: 20 pages, 5 captioned figures, 4 tables, authors from page 15,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/307
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