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 outpatients’ 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 outpatients’ 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$\alpha$ 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$_*>10^{11}$ M$_{\odot}$ 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