914 research outputs found
Perceived Realism of Pedestrian Crowds Trajectories in VR
Crowd simulation algorithms play an essential role in populating Virtual Reality (VR) environments with multiple autonomous humanoid agents. The generation of plausible trajectories can be a significant computational cost for real-time graphics engines, especially in untethered and mobile devices such as portable VR devices. Previous research explores the plausibility and realism of crowd simulations on desktop computers but fails to account the impact it has on immersion. This study explores how the realism of crowd trajectories affects the perceived immersion in VR. We do so by running a psychophysical experiment in which participants rate the realism of real/synthetic trajectories data, showing similar level of perceived realism
Multi-line Herschel/HIFI observations of water reveal infall motions and chemical segregation around high-mass protostars
(Abridged) We use HIFI maps of the 987 GHz H2O 2(02)-1(11) emission to
measure the sizes and shapes of 19 high-mass protostellar envelopes. To
identify infall, we use HIFI spectra of the optically thin C18O 9-8 and H2O-18
1(11)-0(00) lines. The high-J C18O line traces the warm central material and
redshifted H2O-18 1(11)-0(00) absorption indicates material falling onto the
warm core. We probe small-scale chemical differentiation by comparing H2O 752
and 987 GHz spectra with those of H2O-18.
Our measured radii of the central part of the H2O 2(02)-1(11) emission are
30-40% larger than the predictions from spherical envelope models, and axis
ratios are <2, which we consider good agreement. For 11 of the 19 sources, we
find a significant redshift of the H2O-18 1(11)-0(00) line relative to C18O
9-8. The inferred infall velocities are 0.6-3.2 km/s, and estimated mass inflow
rates range from 7e-5 to 2e-2 M0/yr, with the highest mass inflow rates
occurring toward the sources with the highest masses, and possibly the youngest
ages. The other sources show either expanding motions or H2O-18 lines in
emission. The H2O-18 1(11)-0(00) line profiles are remarkably similar to the
"differences" between the H2O 2(02)-1(11) and 2(11)-2(02) profiles, suggesting
that the H2O-18 line and the H2O 2(02)-1(11) absorption originate just inside
the radius where water evaporates from grains, typically 1000-5000 au from the
center. In some sources, the H2O-18 line is detectable in the outflow, where no
C18O emission is seen.
Together, the H2O-18 absorption and C18O emission profiles show that the
water abundance around high-mass protostars has at least three levels: low in
the cool outer envelope, high within the 100 K radius, and very high in the
outflowing gas. Thus, despite the small regions, the combination of lines
presented here reveals systematic inflows and chemical information about the
outflows.Comment: Accepted for publication in Astronomy & Astrophysics; 10 pages body +
10 pages appendi
Periodic variations in the O-C diagrams of five pulsation frequencies of the DB white dwarf EC 20058-5234
Variations in the pulsation arrival time of five independent pulsation frequencies of the DB white dwarf
EC 20058â5234 individually imitate the effects of reflex motion induced by a planet or companion but are
inconsistent when considered in unison. The pulsation frequencies vary periodically in a 12.9 year cycle and
undergo secular changes that are inconsistent with simple neutrino plus photon-cooling models. The magnitude of
the periodic and secular variations increases with the period of the pulsations, possibly hinting that the corresponding
physical mechanism is located near the surface of the star. The phase of the periodic variations appears coupled
to the sign of the secular variations. The standards for pulsation-timing-based detection of planetary companions
around pulsating white dwarfs, and possibly other variables such as subdwarf B stars, should be re-evaluated.
The physical mechanism responsible for this surprising result may involve a redistribution of angular momentum
or a magnetic cycle. Additionally, variations in a supposed combination frequency are shown to match the sum
of the variations of the parent frequencies to remarkable precision, an expected but unprecedented confirmation
of theoretical predictions.Web of Scienc
Design and Vertical Tests of SPS-series Double-Quarter Wave (DQW) Cavity Prototypes for the HL-LHC Crab Cavity System
Crab crossing is essential for high-luminosity colliders. The High Luminosity
Large Hadron Collider (HL-LHC) will equip one of its Interaction Points (IP1)
with Double-Quarter Wave (DQW) crab cavities. A DQW cavity is a new generation
of deflecting RF cavities that stands out for its compactness and broad
frequency separation between fundamental and first high-order modes. The
deflecting kick is provided by its fundamental mode. Each HL-LHC DQW cavity
shall provide a nominal deflecting voltage of 3.4 MV, although up to 5.0 MV may
be required. A Proof-of-Principle (PoP) DQW cavity was limited by quench at 4.6
MV. This paper describes a new, highly optimized cavity, designated DQW
SPS-series, which satisfies dimensional, cryogenic, manufacturing and impedance
requirements for beam tests at SPS and operation in LHC. Two prototypes of this
DQW SPS-series were fabricated by US industry and cold tested after following
conventional SRF surface treatment. Both units outperformed the PoP cavity,
reaching a deflecting voltage of 5.3-5.9 MV. This voltage - the highest reached
by a DQW cavity - is well beyond the nominal voltage of 3.4 MV and may even
operate at the ultimate voltage of 5.0MVwith sufficient margin. This paper
covers fabrication, surface preparation and cryogenic RF test results and
implications
Required Skills for Teachers: Information Literacy at the Top
European Conference on Information Literacy (ECIL) 2017: Information Literacy in the Workplace, held in Saint Malo, France, 18-21 SeptemberThis study seeks to contribute to a reflection on teachersâ training and professional development in the field of information literacy, in Portugal. Aspects regarding teacher training and their role as spreaders of knowledge and multipliers of good practices are problematized. UNESCOâs curriculum for teachers and ACRL guidelines are used methodologically as the central thread of this interpretation. From here we seek to explain how a higher education institution â an Institute of Education -, which is devoted to the professional development of educators, including teachers, has engaged in information literacy actions through training interventions, in recent years. The study concludes that through sharing and dialogue within the librarian profession, but also within the sphere of education professionals - teachers and trainers - the best training practices in university libraries can be consolidated. Finally, certain points for reflection and debate concerning this theme are proposed.info:eu-repo/semantics/publishedVersio
Massive Stars in the Quintuplet Cluster
We present near-infrared photometry and K-band spectra of newly-identified
massive stars in the Quintuplet Cluster, one of the three massive clusters
projected within 50 pc of the Galactic Center. We find that the cluster
contains a variety of massive stars, including more unambiguously identified
Wolf-Rayet stars than any cluster in the Galaxy, and over a dozen stars in
earlier stages of evolution, i.e., LBV, Ofpe/WN9, and OB supergiants. One newly
identified star is the second ``Luminous Blue Variable'' in the cluster, after
the ``Pistol Star.'' Given the evolutionary stages of the identified stars, the
cluster appears to be about 4 \pm 1 Myr old, assuming coeval formation. The
total mass in observed stars is \sim 10^3 \Msun, and the implied mass is
\sim 10^4 \Msun, assuming a lower mass cutoff of 1 \Msun and a Salpeter
initial mass function. The implied mass density in stars is at least a few
thousand \Msun pc^{-3}. The newly-identified stars increase the estimated
ionizing flux from this cluster by about an order of magnitude with respect to
earlier estimates, to 10^{50.9} photons/s, or roughly what is required to
ionize the nearby ``Sickle'' HII region (G0.18 - 0.04). The total luminosity
from the massive cluster stars is \Lsun, enough to account
for the heating of the nearby molecular cloud, M0.20 - 0.033. We propose a
picture which integrates most of the major features in this part of the sky,
excepting the non-thermal filaments. We compare the cluster to other young
massive clusters and globular clusters, finding that it is unique in stellar
content and age, except, perhaps, for the young cluster in the central parsec
of the Galaxy. In addition, we find that the cluster is comparable to small
``super star clusters.'
A high resolution line survey of IRC+10216 with Herschel. First results: Detection of warm silicon dicarbide SiC2
We present the first results of a high-spectral-resolution survey of the
carbon-rich evolved star IRC+10216 that was carried out with the HIFI
spectrometer onboard Herschel. This survey covers all HIFI bands, with a
spectral range from 488 to 1901GHz. In this letter we focus on the band-1b
spectrum, in a spectral range 554.5-636.5GHz, where we identified 130 spectral
features with intensities above 0.03 K and a signal-to-noise ratio >5. Detected
lines arise from HCN, SiO, SiS, CS, CO, metal-bearing species and,
surprisingly, silicon dicarbide (SiC2). We identified 55 SiC2 transitions
involving energy levels between 300 and 900 K. By analysing these rotational
lines, we conclude that SiC2 is produced in the inner dust formation zone, with
an abundance of ~2x10^-7 relative to molecular hydrogen. These SiC2 lines have
been observed for the first time in space and have been used to derive an SiC2
rotational temperature of ~204 K and a source-averaged column density of
~6.4x10^15 cm^-2. Furthermore, the high quality of the HIFI data set was used
to improve the spectroscopic rotational constants of SiC2.Comment: A&A HIFI Special Issue, 201
Massive Protostars in the Infrared Dark Cloud MSXDC G034.43+00.24
We present a multiwavelength study of the infrared dark cloud MSXDC
G034.43+00.24. Dust emission, traced by millimeter/submillimeter images
obtained with the IRAM, JCMT, and CSO telescopes, reveals three compact cores
within this infrared dark cloud with masses of 170--800 Msun and sizes < 0.5
pc. Spitzer 3.6-8.0 um images show slightly extended emission toward these
cores, with a spectral enhancement at 4.5 um that probably arises from shocked
H2. In addition, the broad line widths (Delta V ~ 10 km/s) of HCN (4-3), and CS
(3-2), and the detection of SiO (2-1), observed with the JCMT and IRAM
telescopes, also indicate active star formation. Spitzer 24 um images reveal
that each of these cores contains a bright, unresolved continuum source; these
sources are most likely embedded protostars. Their millimeter to mid-IR
continuum spectral energy distributions reveal very high luminosities,
9000-32,000 Lsun. Because such large luminosities cannot arise from low-mass
protostars, MSXDC G034.43+00.24 is actively forming massive (~ 10 Msun) stars.Comment: 6 pages, 3 figures (1 colour), accepted ApJ
Bounded rationality and the Brexit negotiations:Why Britain failed to understand the EU
Research on the Brexit negotiations has linked the problems faced by Britain to flawed assumptions in the UKâs perception of EU interests. These include the idea that the EU would be open to compromise on key principles, that it would offer the UK a bespoke relationship, that national capitals would respond favourably to bilateral initiatives, and that EU unity would not hold. Yet the origins of these assumptions have been subject to little systematic scrutiny. How did such wrong-headed assumptions about the EUâs interests emerge? Drawing on insights from bounded rationality we identify three aspects of the decision-making environment linked with biased thinking: (1) ill-fitting routines and lessons, (2) a lack of decision-making openness, and (3) a lack of EU expertize and contact. We demonstrate our argument using data obtained from interviews in Brussels and London in 2017â18 and accounts of those involved in the decisions
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