9,391 research outputs found
Real-time Monocular Object SLAM
We present a real-time object-based SLAM system that leverages the largest
object database to date. Our approach comprises two main components: 1) a
monocular SLAM algorithm that exploits object rigidity constraints to improve
the map and find its real scale, and 2) a novel object recognition algorithm
based on bags of binary words, which provides live detections with a database
of 500 3D objects. The two components work together and benefit each other: the
SLAM algorithm accumulates information from the observations of the objects,
anchors object features to especial map landmarks and sets constrains on the
optimization. At the same time, objects partially or fully located within the
map are used as a prior to guide the recognition algorithm, achieving higher
recall. We evaluate our proposal on five real environments showing improvements
on the accuracy of the map and efficiency with respect to other
state-of-the-art techniques
Exact Finite-Size-Scaling Corrections to the Critical Two-Dimensional Ising Model on a Torus
We analyze the finite-size corrections to the energy and specific heat of the
critical two-dimensional spin-1/2 Ising model on a torus. We extend the
analysis of Ferdinand and Fisher to compute the correction of order L^{-3} to
the energy and the corrections of order L^{-2} and L^{-3} to the specific heat.
We also obtain general results on the form of the finite-size corrections to
these quantities: only integer powers of L^{-1} occur, unmodified by logarithms
(except of course for the leading term in the specific heat); and the
energy expansion contains only odd powers of L^{-1}. In the specific-heat
expansion any power of L^{-1} can appear, but the coefficients of the odd
powers are proportional to the corresponding coefficients of the energy
expansion.Comment: 26 pages (LaTeX). Self-unpacking file containing the tex file and
three macros (indent.sty, eqsection.sty, subeqnarray.sty). Added discussions
on the results and new references. Version to be published in J. Phys.
On The Reduced Canonical Quantization Of The Induced 2D-Gravity
The quantization of the induced 2d-gravity on a compact spatial section is
carried out in three different ways. In the three approaches the supermomentum
constraint is solved at the classical level but they differ in the way the
hamiltonian constraint is imposed. We compare these approaches establishing an
isomorphism between the resulting Hilbert spaces.Comment: 17 pages, plain LaTeX. FTUV/93-15, IFIC/93-10, Imperial-TP/93-94/1
An epidemiological study of burglary offenders: trends and predictors of self-reported arrests for burglary in the United States, 2002-2013
Burglary is serious property crime with a relatively high incidence and has been shown to be variously associated with other forms of criminal behavior. Unfortunately, an epidemiological understanding of burglary and its correlates is largely missing from the literature. Using public-use data collected between 2002 and 2013 as part of the National Survey on Drug Use and Health (NSDUH), the current study compared those who self-reported burglary arrest in the prior 12 months with and without criminal history. The unadjusted prevalence estimates of self-reported burglary arrest were statistically different for those with a prior arrest history (4.7%) compared with those without an arrest history (0.02%) which is a 235-fold difference. Those with an arrest history were more likely to report lower educational attainment, to have lower income, to have moved more than 3 times in the past 5 years, and to use alcohol, tobacco, illicit drugs, and engage in binge drinking. Moreover, those with prior arrest histories were younger and more likely to be male. There is considerable heterogeneity among burglars with criminal history indicating substantially greater behavioral risk
Weyl Invariance and Black Hole Evaporation
We consider the semiclassical dynamics of CGHS black holes with a
Weyl-invariant effective action for conformal matter. The trace anomaly of
Polyakov effective action is converted into the Virasoro anomaly thus leading
to the same flux of Hawking radiation. The covariance of semiclassical
equations can be restored through a non-local redefinition of the
metric-dilaton fields. The resulting theory turns out to be equivalent to the
RST model. This provides a mechanism to solve semiclassical equations of 2D
dilaton gravity coupled to conformal matter for classically soluble models.Comment: LaTeX, needs amssymb, 8 pages. One reference adde
Direct estimation of electron density in the Orion Bar PDR from mm-wave carbon recombination lines
A significant fraction of the molecular gas in star-forming regions is
irradiated by stellar UV photons. In these environments, the electron density
(n_e) plays a critical role in the gas dynamics, chemistry, and collisional
excitation of certain molecules. We determine n_e in the prototypical strongly
irradiated photodissociation region (PDR), the Orion Bar, from the detection of
new millimeter-wave carbon recombination lines (mmCRLs) and existing far-IR
[13CII] hyperfine line observations. We detect 12 mmCRLs (including alpha,
beta, and gamma transitions) observed with the IRAM 30m telescope, at ~25''
angular resolution, toward the H/H2 dissociation front (DF) of the Bar. We also
present a mmCRL emission cut across the PDR. These lines trace the C+/C/CO gas
transition layer. As the much lower frequency carbon radio recombination lines,
mmCRLs arise from neutral PDR gas and not from ionized gas in the adjacent HII
region. This is readily seen from their narrow line profiles (dv=2.6+/-0.4
km/s) and line peak LSR velocities (v_LSR=+10.7+/-0.2 km/s). Optically thin
[13CII] hyperfine lines and molecular lines - emitted close to the DF by trace
species such as reactive ions CO+ and HOC+ - show the same line profiles. We
use non-LTE excitation models of [13CII] and mmCRLs and derive n_e = 60-100
cm^-3 and T_e = 500-600 K toward the DF. The inferred electron densities are
high, up to an order of magnitude higher than previously thought. They provide
a lower limit to the gas thermal pressure at the PDR edge without using
molecular tracers. We obtain P_th > (2-4)x10^8 cm^-3 K assuming that the
electron abundance is equal or lower than the gas-phase elemental abundance of
carbon. Such elevated thermal pressures leave little room for magnetic pressure
support and agree with a scenario in which the PDR photoevaporates.Comment: Accepted for publication in A&A Letters (includes language editor
corrections
- …