564 research outputs found
Efficient AoA-based wireless indoor localization for hospital outpatients using mobile devices
The motivation of this work is to help outpatients find their corresponding departments or clinics, thus, it needs to provide indoor positioning services with a room-level accuracy. Unlike wireless outdoor localization that is dominated by the global positioning system (GPS), wireless indoor localization is still an open issue. Many different schemes are being developed to meet the increasing demand for indoor localization services. In this paper, we investigated the AoA-based wireless indoor localization for outpatientsâ wayfinding in a hospital, where Wi-Fi access points (APs) are deployed, in line, on the ceiling. The target position can be determined by a mobile device, like a smartphone, through an efficient geometric calculation with two known APs coordinates and the angles of the incident radios. All possible positions in which the target may appear have been comprehensively investigated, and the corresponding solutions were proven to be the same. Experimental results show that localization error was less than 2.5 m, about 80% of the time, which can satisfy the outpatientsâ requirements for wayfinding
The NGC 4013 tale: a pseudo-bulged, late-type spiral shaped by a major merger
Many spiral galaxy haloes show stellar streams with various morphologies when
observed with deep images. The origin of these tidal features is discussed,
either coming from a satellite infall or caused by residuals of an ancient,
gas-rich major merger. By modelling the formation of the peculiar features
observed in the NGC 4013 halo, we investigate their origin. By using GADGET -2
with implemented gas cooling, star formation, and feedback, we have modelled
the overall NGC 4013 galaxy and its associated halo features. A gas-rich major
merger occurring 2.7-4.6 Gyr ago succeeds in reproducing the NGC 4013 galaxy
properties, including all the faint stellar features, strong gas warp,
boxy-shaped halo and vertical 3.6 mum luminosity distribution. High gas
fractions in the progenitors are sufficient to reproduce the observed thin and
thick discs, with a small bulge fraction, as observed. A major merger is able
to reproduce the overall NGC 4013 system, including the warp strength, the red
colour and the high stellar mass density of the loop, while a minor merger
model cannot. Because the gas-rich model suffices to create a pseudo-bulge with
a small fraction of the light, NGC 4013 is perhaps the archetype of a late-type
galaxy formed by a relatively recent merger. Then late type, pseudo-bulge
spirals are not mandatorily made through secular evolution, and the NGC 4013
properties also illustrate that strong warps in isolated galaxies may well
occur at a late phase of a gas-rich major merger.Comment: 11 pages,9 figures,accepted for publication in MNRA
Does the dwarf galaxy system of the Milky Way originate from Andromeda?
The Local Group is often seen to be a quiescent environment without
significant merger events. However an ancient major merger may have occurred in
the most massive galaxy. Numerical simulations have shown that tidal tails
formed during gas-rich major mergers are long-lived and could be responsible
for old stellar streams and likely induce the formation of tidal dwarf galaxies
(TDGs). Using several hydrodynamical simulations we have investigated the most
prominent tidal tail formed during the first passage, which is gas-rich and
contains old and metal poor stars. We discovered several striking coincidences
after comparing its location and motion to those of the Milky Way (MW) and of
the Magellanic Clouds (MCs). First, the tidal tail is sweeping a relatively
small volume in which the MW precisely lies. Because the geometry of the merger
is somehow fixed by the anisotropic properties of the Giant Stream (GS), we
evaluate the chance of the MW to be at such a rendez-vous with this gigantic
tidal tail to be 5 %. Second, the velocity of the tidal tail matches the LMC
proper motion, and reproduce quite well the geometrical and angular momentum
properties of the MW dwarfs, i.e. the so-called disk of satellites, better
called Vast Polar Structure (VPOS). Third, the simulation of the tidal tail
reveals one of the formed TDG with mass and location almost comparable to those
of the LMC. Our present modeling is however too limited to study the detailed
interaction of gas-rich TDGs with the potential of the MW, and a complementary
study is required to test whether the dwarf intrinsic properties can be
accounted for by our scenario. Nevertheless this study suggests a causal link
between an ancient, gas-rich major merger at the M31 location, and several
enigma in the Local Group, the GS, the VPOS, and the presence of the MCs.Comment: 17 pages accepted MNRA
Curvy surface conformal ultra-thin transfer printed Si optoelectronic penetrating microprobe arrays
Penetrating neural probe arrays are powerful bio-integrated devices for studying basic neuroscience and applied neurophysiology, underlying neurological disorders, and understanding and regulating animal and human behavior. This paper presents a penetrating microprobe array constructed in thin and flexible fashion, which can be seamlessly integrated with the soft curvy substances. The function of the microprobes is enabled by transfer printed ultra-thin Si optoelectronics. As a proof-of-concept device, microprobe array with Si photodetector arrays are demonstrated and their capability of mapping the photo intensity in space are illustrated. The design strategies of utilizing thin polyimide based microprobes and supporting substrate, and employing the heterogeneously integrated thin optoelectronics are keys to accomplish such a device. The experimental and theoretical investigations illustrate the materials, manufacturing, mechanical and optoelectronic aspects of the device. While this paper primarily focuses on the device platform development, the associated materials, manufacturing technologies, and device design strategy are applicable to more complex and multi-functionalities in penetrating probe array-based neural interfaces and can also find potential utilities in a wide range of bio-integrated systems
Morphological Dependence of Star Formation Properties for the Galaxies in the Merging Galaxy Cluster A2255
The merging cluster of galaxies A2255 is covered by the Sloan Digital Sky
Survey (SDSS) survey. In this paper we perform a morphological classification
on the basis of the SDSS imaging and spectral data, and investigate the
morphological dependence of the star formation rates (SFRs) for these member
galaxies. As we expect, a tight correlation between the normalized SFR by
stellar mass (SFR/M) and the H equivalent width is found for the
late-type galaxies in A2255. The correlation of SFR/M with the continuum
break strength at 4000 \AA is also confirmed. The SFR/M - M correlation
is found for both the early- and late-type galaxies, indicating that the star
formation activity tends to be suppressed when the assembled stellar mass
M) increases, and this correlation is tighter and steeper for the late-type
cluster galaxies. Compared with the mass range of field spiral galaxies, only
two massive late-type galaxies with M M are survived in
A2255, suggesting that the gas disks of massive spiral galaxies could have been
tidally stripped during cluster formation. Additionally, the SFR variation with
the projected radial distance are found to be heavily dependent upon galaxy
morphology: the early-type galaxies have a very weak inner decrease in
SFR/M, while the inner late-type galaxies tend to have higher SFR/M
values than the outer late-types. This may suggest that the galaxy-scale
turbulence stimulated by the merging of subclusters might have played different
roles on early- and late-type galaxies, which leads to a suppression of the
star formation activity for E/S0 galaxies and a SFR enhancement for spiral and
irregular galaxies.Comment: 21 pages, including 7 EPS figures and 1 tables, uses aastex.cls,
Accepted by the A
Reproducing properties of MW dSphs as descendants of DM-free TDGs
The Milky Way (MW) dwarf spheroidal (dSph) satellites are known to be the
most dark-matter (DM) dominated galaxies with estimates of dark to baryonic
matter reaching even above one hundred. It comes from the assumption that
dwarfs are dynamically supported by their observed velocity dispersions.
However their spatial distributions around the MW is not at random and this
could challenge their origin, previously assumed to be residues of primordial
galaxies accreted by the MW potential. Here we show that alternatively, dSphs
could be the residue of tidal dwarf galaxies (TDGs), which would have
interacted with the Galactic hot gaseous halo and disk. TDGs are gas-rich and
have been formed in a tidal tail produced during an ancient merger event at the
M31 location, and expelled towards the MW. Our simulations show that low-mass
TDGs are fragile to an interaction with the MW disk and halo hot gas. During
the interaction, their stellar content is progressively driven out of
equilibrium and strongly expands, leading to low surface brightness feature and
mimicking high dynamical M/L ratios. Our modeling can reproduce the properties,
including the kinematics, of classical MW dwarfs within the mass range of the
Magellanic Clouds to Draco. An ancient gas-rich merger at the M31 location
could then challenge the currently assumed high content of dark matter in dwarf
galaxies. We propose a simple observational test with the coming GAIA mission,
to follow their expected stellar expansion, which should not be observed within
the current theoretical framework.Comment: 17 pages, 11 figures, accepted by the Monthly Notices of the Royal
Astronomical Society (MNRAS
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