1,555 research outputs found
Low-effort place recognition with WiFi fingerprints using deep learning
Using WiFi signals for indoor localization is the main localization modality
of the existing personal indoor localization systems operating on mobile
devices. WiFi fingerprinting is also used for mobile robots, as WiFi signals
are usually available indoors and can provide rough initial position estimate
or can be used together with other positioning systems. Currently, the best
solutions rely on filtering, manual data analysis, and time-consuming parameter
tuning to achieve reliable and accurate localization. In this work, we propose
to use deep neural networks to significantly lower the work-force burden of the
localization system design, while still achieving satisfactory results.
Assuming the state-of-the-art hierarchical approach, we employ the DNN system
for building/floor classification. We show that stacked autoencoders allow to
efficiently reduce the feature space in order to achieve robust and precise
classification. The proposed architecture is verified on the publicly available
UJIIndoorLoc dataset and the results are compared with other solutions
Heavy Ion Physics at the LHC with the ATLAS Detector
The ATLAS detector at CERN will provide a high-resolution
longitudinally-segmented calorimeter and precision tracking for the upcoming
study of heavy ion collisions at the LHC (sqrt(s_NN)=5520 GeV). The calorimeter
covers |eta|<5 with both electromagnetic and hadronic sections, while the inner
detector spectrometer covers |eta|<2.5. ATLAS will study a full range of
observables necessary to characterize the hot and dense matter formed at the
LHC. Global measurements (particle multiplicities, collective flow) will
provide access into its thermodynamic and hydrodynamic properties. Measuring
complete jets out to 100's of GeV will allow detailed studies of energy loss
and its effect on jets. Quarkonia will provide a handle on deconfinement
mechanisms. ATLAS will also study the structure of the nucleon and nucleus
using forward physics probes and ultraperipheral collisions, both enabled by
segmented Zero Degree Calorimeters.Comment: 9 pages, 8 figures, submitted to the Proceedings of Quark Matter
2006, Shanghai, China, November 14-20, 200
The formation of the eccentric-orbit millisecond pulsar J1903+0327 and the origin of single millisecond pulsars
The millisecond pulsar J1903+0327 is accompanied by an ordinary G-dwarf star
in an unusually wide (\,days) and eccentric () orbit. The standard model for producing MSPs fails to explain the
orbital characteristics of this extraordinary binary, and alternative binary
models are unable to explain the observables. We present a triple-star model
for producing MSPs in relatively wide eccentric binaries with a normal
(main-sequence) stellar companion. We start from a stable triple system
consisting of a Low-Mass X-ray Binary (LMXB) with an orbital period of at least
1 day, accompanied by a G-dwarf in a wide and possibly eccentric orbit.
Variations in the initial conditions naturally provide a satisfactory
explanation for the unexplained triple component in the eclipsing soft X-ray
transient 4U~2129+47 or the cataclysmic variable EC 19314-5915. The best
explanation for J1903, however, results from the expansion of the orbit of the
LMXB, driven by the mass transfer from the evolving donor star to its neutron
star companion, which causes the triple eventually to becomes dynamically
unstable. Using numerical computations we show that, depending on the precise
system configuration at the moment the triple becomes dynamically unstable, the
ejection of each of the three components is possible. If the donor star of the
LMXB is ejected, a system resembling J1903, will result. If the neutron star is
ejected, a single MSP results. This model therefore also provides a
straightforward mechanism for forming single MSP in the Galactic disk. We
conclude that the Galaxy contains some 30--300 binaries with characteristics
similar to J1903, and about an order of magnitude fewer single millisecond
pulsars produced with the proposed triple scenario.Comment: ApJ accepted for publicatio
The Mid-Infrared Instrument for the James Webb Space Telescope, V: Predicted Performance of the MIRI Coronagraphs
The imaging channel on the Mid-Infrared Instrument (MIRI) is equipped with
four coronagraphs that provide high contrast imaging capabilities for studying
faint point sources and extended emission that would otherwise be overwhelmed
by a bright point-source in its vicinity. Such bright sources might include
stars that are orbited by exoplanets and circumstellar material, mass-loss
envelopes around post-main-sequence stars, the near-nuclear environments in
active galaxies, and the host galaxies of distant quasars. This paper describes
the coronagraphic observing modes of MIRI, as well as performance estimates
based on measurements of the MIRI flight model during cryo-vacuum testing. A
brief outline of coronagraphic operations is also provided. Finally, simulated
MIRI coronagraphic observations of a few astronomical targets are presented for
illustration
New Insights into the Problem of the Surface Gravity Distribution of Cool DA White Dwarfs
We review at length the longstanding problem in the spectroscopic analysis of
cool hydrogen-line (DA) white dwarfs (Teff < 13,000 K) where gravities are
significantly higher than those found in hotter DA stars. The first solution
that has been proposed for this problem is a mild and systematic helium
contamination from convective mixing that would mimic the high gravities. We
constrain this scenario by determining the helium abundances in six cool DA
white dwarfs using high-resolution spectra from the Keck I 10-m telescope. We
obtain no detections, with upper limits as low as He/H = 0.04 in some cases.
This allows us to put this scenario to rest for good. We also extend our model
grid to lower temperatures using improved Stark profiles with non-ideal gas
effects from Tremblay & Bergeron and find that the gravity distribution of cool
objects remains suspiciously high. Finally, we find that photometric masses
are, on average, in agreement with expected values, and that the high-log g
problem is so far unique to the spectroscopic approach.Comment: 44 pages, 14 figures, accepted for publication in the Astrophysical
Journa
On the Interpretation of High Velocity White Dwarfs as Members of the Galactic Halo
A detailed analysis of 32 of the 38 halo white dwarf candidates identified by
Oppenheimer et al. is presented, based on model atmosphere fits to observed
energy distributions built from optical BVRI and infrared JHK CCD photometry.
Effective temperatures and atmospheric compositions are determined for all
objects, as well as masses and cooling ages when trigonometric parallax
measurements are available. This sample is combined with that of other halo
white dwarf candidates and disk white dwarfs to study the nature of these
objects in terms of reduced proper motion diagrams, tangential velocities, and
stellar ages. We reaffirm the conclusions of an earlier analysis based on
photographic magnitudes of the same sample that total stellar ages must be
derived in order to associate a white dwarf with the old halo population, and
that this can only be accomplished through precise mass and distance
determinations.Comment: 31 pages, 8 figures, accepted for publication in the Astrophysical
Journa
High Level of Soluble HLA-G in the Female Genital Tract of Beninese Commercial Sex Workers Is Associated with HIV-1 Infection
Most HIV infections are transmitted across mucosal epithelium. Understanding the role of innate and specific mucosal immunity in susceptibility or protection against HIV infection, as well as the effect of HIV infection on mucosal immunity, are of fundamental importance. HLA-G is a powerful modulator of the immune response. The aim of this study was to investigate whether soluble HLA-G (sHLA-G) expression in the female genital tract is associated with HIV-1 infection.Genital levels of sHLA-G were determined in 52 HIV-1-uninfected and 44 antiretroviral naïve HIV-1-infected female commercial sex workers (CSWs), as well as 71 HIV-1-uninfected non-CSW women at low risk of exposure, recruited in Cotonou, Benin. HIV-1-infected CSWs had higher genital levels of sHLA-G compared with those in both the HIV-1-uninfected CSW (P = 0.009) and non-CSW groups (P = 0.0006). The presence of bacterial vaginosis (P = 0.008), and HLA-G*01:01:02 genotype (P = 0.002) were associated with higher genital levels of sHLA-G in the HIV-1-infected CSWs, whereas the HLA-G*01:04:04 genotype was also associated with higher genital level of sHLA-G in the overall population (P = 0.038). When adjustment was made for all significant variables, the increased expression of sHLA-G in the genital mucosa remained significantly associated with both HIV-1 infection (P = 0.02) and bacterial vaginosis (P = 0.03).This study demonstrates that high level of sHLA-G in the genital mucosa is independently associated with both HIV-1 infection and bacterial vaginosis
Search for positively charged strangelets and other related results with E864 at the AGS
We report on the latest results in the search for positively charged
strangelets from E864's 96/97 run at the AGS with sensitivity of about per central collision. This contribution also contains new results of
a search for highly charged strangelets with . Production of light
nuclei, such as and , is presented as well. Measurements of yields
of these rarely produced isotopes near midrapidity will help constrain the
production levels of strangelets via coalescence. E864 also measures antiproton
production which includes decays from antihyperons. Comparisons with antiproton
yields measured by E878 as a function of centrality indicate a large
antihyperon-to-antiproton ratio in central collisions.Comment: 8 pages, 4 figures; Talk at SQM'98, Padova, Italy (July 20-24th,
1998
Using Online Digital Tools and Video to Support International Problem-Based Learning
The goal of this study is to examine how to facilitate cross-cultural groups in problem-based learning (PBL) using online digital tools and videos. The PBL consisted of two video-based cases used to trigger student-learning issues about giving bad news to HIV-positive patients. Mixed groups of medical students from Canada and Hong Kong worked with facilitators from each country along with an expert facilitator. The study used AdobeConnect to support the international model through synchronous video interaction and shared applications. This study examines strategies and challenges in facilitating PBL across distance and cultures. Discourse was analyzed using both an inductive and deductive approach where the later used the Community of Inquiry coding scheme. The international context provides a way to facilitate multiple perspectives about how to communicate bad news to patients from different cultural backgrounds. In addition, we present the results of an exploratory analysis of pre and post tests using a standardized patient that demonstrate that the students’ pattern of communication showed qualitative change. Several conjectures were developed for future research
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