Fall detection using history triple features

Accurate identification and timely handling of involuntary events, such as falls, plays a crucial part in effective as-sistive environment systems. Fall detection, in particular, is quite critical, especially in households of lonely elderly people. However, the task of visually identifying a fall is challenging as there is a variety of daily activities that can be mistakenly characterized as falls. To tackle this issue, various feature extraction methods that aim to effectively distinguish unintentional falls from other everyday activi-ties have been proposed. In this study, we examine the capability of the History Triple Features technique based on Trace transform, to provide noise robust and invariant to different variations features for the spatiotemporal represen-tation of fall occurrences. The aim is to effectively detect falls among other household-related activities that usually take place indoors. For the evaluation of the algorithm the video sequences from two realistic fall detection datasets of different nature have been used. One is constructed using a ceiling mounted depth camera and the other is constructed using an RGB camera placed on arbitrary positions in dif-ferent rooms. After forming the feature vectors, we train a support vector machine using a radial basis function kernel. Results show a very good response of the algorithm achiev-ing 100 % on both datasets indicating the suitability of the technique to the specific task. 1

Cool Young Stars in the Northern Hemisphere: Beta Pictoris and AB Doradus Moving Group Candidates

As part of our continuing effort to identify new, low-mass members of nearby, young moving groups (NYMGs), we present a list of young, low-mass candidates in the northern hemisphere. We used our proven proper motion selection procedure and ROSAT-X-ray and GALEX-UV activity indicators to identify 204 young stars as candidate members of the Beta Pictoris and AB Doradus NYMGs. Definitive membership assignment of a given candidate will require a measurement of its radial velocity and distance. We present a simple system of indices to characterize the young candidates and help prioritize follow up observations. New group members identified in this candidate list will be high priority targets for: 1) exoplanet direct imaging searches, 2) the study of post-T-Tauri astrophysics, 3) understanding recent local star formation, and 4) the study of local galactic kinematics. Information available now allows us to identify 8 likely new members in the list. Two of these, a late-K and an early-M dwarf, we find to be likely members of the Beta Pic group. The other six stars are likely members of the AB Dor moving group. These include an M dwarf triple system, and three very cool objects that may be young brown dwarfs, making them the lowest-mass, isolated objects proposed in the AB Dor moving group to date.Comment: 41 pages, 15 figures, Accepted to the Astronomical Journa

A Deep Radio Survey of Abell 2125 III: The Cluster Core - Merging and Stripping

We use radio, near-IR, optical, and X-ray observations to examine dynamic processes in the central region of Abell 2125. In addition to the central triple, including members of both major dynamical subsystems identified from a redshift survey, this region features a galaxy showing strong evidence for ongoing gas stripping during a high-velocity passage through the gas in the cluster core. The disk galaxy C153 exhibits a plume stretching toward the cluster center seen in soft X-rays by Chandra, parts of which are also seen in [O II] emission and near-UV continuum light. HST imaging shows a distorted disk, with star-forming knots asymmetrically distributed and remnant spiral structure possibly defined by dust lanes. The stars and ionized gas in its disk are kinematically decoupled, demonstrating that pressure stripping must be important, and that tidal disruption is not the only mechanism at work. Comparison of the gas properties seen in the X-ray and optical data on the plume highlight significant features of the history of stripped gas in the intracluster medium. The nucleus of C153 also hosts an AGN, shown by the weak and distorted extended radio emission and a radio compact core. The unusual strength of the stripping signatures in this instance is likely related to the high relative velocity of the galaxy with respect to the intracluster medium, during a cluster/cluster merger, and its passage very near the core of the cluster. Another sign of recent dynamical events is diffuse starlight asymmetrically placed about the central triple in a cD envelope. Transient and extreme dynamical events as seen in Abell 2125 may be important drivers of galaxy evolution in the cores of rich clusters.Comment: 36 pages, 16 figures, accepted AJ, paper with full resolution figures is available at http:www.aoc.nrao.edu/~fowen/papers/a2125/a2125paper3.ps.g

Triplets of supermassive black holes: Astrophysics, Gravitational Waves and Detection

Supermassive black holes (SMBHs) found in the centers of many galaxies have been recognized to play a fundamental active role in the cosmological structure formation process. In hierarchical formation scenarios, SMBHs are expected to form binaries following the merger of their host galaxies. If these binaries do not coalesce before the merger with a third galaxy, the formation of a black hole triple system is possible. Numerical simulations of the dynamics of triples within galaxy cores exhibit phases of very high eccentricity (as high as $e \sim 0.99$). During these phases, intense bursts of gravitational radiation can be emitted at orbital periapsis. This produces a gravitational wave signal at frequencies substantially higher than the orbital frequency. The likelihood of detection of these bursts with pulsar timing and the Laser Interferometer Space Antenna ({\it LISA}) is estimated using several population models of SMBHs with masses $\gtrsim 10^7 {\rm M_\odot}$. Assuming a fraction of binaries $\ge 0.1$ in triple system, we find that few to few dozens of these bursts will produce residuals $>1$ ns, within the sensitivity range of forthcoming pulsar timing arrays (PTAs). However, most of such bursts will be washed out in the underlying confusion noise produced by all the other 'standard' SMBH binaries emitting in the same frequency window. A detailed data analysis study would be required to assess resolvability of such sources. Implementing a basic resolvability criterion, we find that the chance of catching a resolvable burst at a one nanosecond precision level is 2-50%, depending on the adopted SMBH evolution model. On the other hand, the probability of detecting bursts produced by massive binaries (masses \gtrsim 10^7\msun) with {\it LISA} is negligible.Comment: Accepted for publication by MNRAS, minor change

A stigmergy-based analysis of city hotspots to discover trends and anomalies in urban transportation usage

A key aspect of a sustainable urban transportation system is the effectiveness of transportation policies. To be effective, a policy has to consider a broad range of elements, such as pollution emission, traffic flow, and human mobility. Due to the complexity and variability of these elements in the urban area, to produce effective policies remains a very challenging task. With the introduction of the smart city paradigm, a widely available amount of data can be generated in the urban spaces. Such data can be a fundamental source of knowledge to improve policies because they can reflect the sustainability issues underlying the city. In this context, we propose an approach to exploit urban positioning data based on stigmergy, a bio-inspired mechanism providing scalar and temporal aggregation of samples. By employing stigmergy, samples in proximity with each other are aggregated into a functional structure called trail. The trail summarizes relevant dynamics in data and allows matching them, providing a measure of their similarity. Moreover, this mechanism can be specialized to unfold specific dynamics. Specifically, we identify high-density urban areas (i.e hotspots), analyze their activity over time, and unfold anomalies. Moreover, by matching activity patterns, a continuous measure of the dissimilarity with respect to the typical activity pattern is provided. This measure can be used by policy makers to evaluate the effect of policies and change them dynamically. As a case study, we analyze taxi trip data gathered in Manhattan from 2013 to 2015.Comment: Preprin

Average Metallicity and Star Formation Rate of Lya Emitters Probed by a Triple Narrow-Band Survey

We present the average metallicity and star-formation rate of Lya emitters (LAEs) measured from our large-area survey with three narrow-band (NB) filters covering the Lya, [OII]3727, and Ha+[NII] lines of LAEs at z=2.2. We select 919 z=2.2 LAEs from Subaru/Suprime-Cam NB data in conjunction with Magellan/IMACS spectroscopy. Of these LAEs, 561 and 105 are observed with KPNO/NEWFIRM near-infrared NB filters whose central wavelengths are matched to redshifted [OII] and Ha nebular lines, respectively. By stacking the near-infrared images of the LAEs, we successfully obtain average nebular-line fluxes of LAEs, the majority of which are too faint to be identified individually by narrow-band imaging or deep spectroscopy. The stacked object has an Ha luminosity of 1.7x10^{42} erg s^{-1} corresponding to a star formation rate (SFR) of 14 M_{sun} yr^{-1}. We place, for the first time, a firm lower limit to the average metallicity of LAEs of Z>~0.09 Z_{sun} (2sigma) based on the [OII]/(Ha+[NII]) index together with photo-ionization models and empirical relations. This lower limit of metallicity rules out the hypothesis that LAEs, so far observed at z~2, are extremely metal poor (Z<2x10^{-2} Z_{sun}) young galaxies at the 4sigma level. This limit is higher than a simple extrapolation of the observed mass-metallicity relation of z~2 UV-selected galaxies toward lower masses (5x10^{8} M_{sun}), but roughly consistent with a recently proposed fundamental mass-metallicity relation when the LAEs' relatively low SFR is taken into account. The Ha and Lya luminosities of our NB-selected LAEs indicate that the escape fraction of Lya photons is ~12-30 %, much higher than the values derived for other galaxy populations at z~2.Comment: 21 pages, 15 figures, 8 tables. Accepted for publication in Ap

Knowledge will Propel Machine Understanding of Content: Extrapolating from Current Examples

Machine Learning has been a big success story during the AI resurgence. One particular stand out success relates to learning from a massive amount of data. In spite of early assertions of the unreasonable effectiveness of data, there is increasing recognition for utilizing knowledge whenever it is available or can be created purposefully. In this paper, we discuss the indispensable role of knowledge for deeper understanding of content where (i) large amounts of training data are unavailable, (ii) the objects to be recognized are complex, (e.g., implicit entities and highly subjective content), and (iii) applications need to use complementary or related data in multiple modalities/media. What brings us to the cusp of rapid progress is our ability to (a) create relevant and reliable knowledge and (b) carefully exploit knowledge to enhance ML/NLP techniques. Using diverse examples, we seek to foretell unprecedented progress in our ability for deeper understanding and exploitation of multimodal data and continued incorporation of knowledge in learning techniques.Comment: Pre-print of the paper accepted at 2017 IEEE/WIC/ACM International Conference on Web Intelligence (WI). arXiv admin note: substantial text overlap with arXiv:1610.0770