3,079 research outputs found
MaestROB: A Robotics Framework for Integrated Orchestration of Low-Level Control and High-Level Reasoning
This paper describes a framework called MaestROB. It is designed to make the
robots perform complex tasks with high precision by simple high-level
instructions given by natural language or demonstration. To realize this, it
handles a hierarchical structure by using the knowledge stored in the forms of
ontology and rules for bridging among different levels of instructions.
Accordingly, the framework has multiple layers of processing components;
perception and actuation control at the low level, symbolic planner and Watson
APIs for cognitive capabilities and semantic understanding, and orchestration
of these components by a new open source robot middleware called Project Intu
at its core. We show how this framework can be used in a complex scenario where
multiple actors (human, a communication robot, and an industrial robot)
collaborate to perform a common industrial task. Human teaches an assembly task
to Pepper (a humanoid robot from SoftBank Robotics) using natural language
conversation and demonstration. Our framework helps Pepper perceive the human
demonstration and generate a sequence of actions for UR5 (collaborative robot
arm from Universal Robots), which ultimately performs the assembly (e.g.
insertion) task.Comment: IEEE International Conference on Robotics and Automation (ICRA) 2018.
Video: https://www.youtube.com/watch?v=19JsdZi0TW
The su(N) XX model
The natural su(N) generalization of the XX model is introduced and analyzed.
It is defined in terms of the characterizing properties of the usual XX model:
the existence of two infinite sequences of mutually commuting conservation laws
and the existence of two infinite sequences of mastersymmetries. The
integrability of these models, which cannot be obtained in a degenerate limit
of the su(N)-XXZ model, is established in two ways: by exhibiting their R
matrix and from a direct construction of the commuting conservation laws. We
then diagonalize the conserved laws by the method of the algebraic Bethe
Ansatz. The resulting spectrum is trivial in a certain sense; this provides
another indication that the su(N) XX model is the natural generalization of the
su(2) model. The application of these models to the construction of an
integrable ladder, that is, an su(N) version of the Hubbard model, is
mentioned.Comment: 16 pages, TeX and harvmac (option b). Minor corrections, accepted for
publication in Nuclear Physics
Millimeter imaging of HD 163296: probing the disk structure and kinematics
We present new multi-wavelength millimeter interferometric observations of
the Herbig Ae star HD 163296 obtained with the IRAM/PBI, SMA and VLA arrays
both in continuum and in the 12CO, 13CO and C18O emission lines. Gas and dust
properties have been obtained comparing the observations with self-consistent
disk models for the dust and CO emission. The circumstellar disk is resolved
both in the continuum and in CO. We find strong evidence that the circumstellar
material is in Keplerian rotation around a central star of 2.6 Msun. The disk
inclination with respect to the line of sight is 46+-4 deg with a position
angle of 128+-4 deg. The slope of the dust opacity measured between 0.87 and 7
mm (beta=1) confirms the presence of mm/cm-size grains in the disk midplane.
The dust continuum emission is asymmetric and confined inside a radius of 200
AU while the CO emission extends up to 540 AU. The comparison between dust and
CO temperature indicates that CO is present only in the disk interior. Finally,
we obtain an increasing depletion of CO isotopomers from 12CO to 13CO and C18O.
We argue that these results support the idea that the disk of HD 163296 is
strongly evolved. In particular, we suggest that there is a strong depletion of
dust relative to gas outside 200 AU; this may be due to the inward migration of
large bodies that form in the outer disk or to clearing of a large gap in the
dust distribution by a low mass companion.Comment: Accepted for publication on A&A, 16 page
Recommended from our members
When to start ART in Africa.
To the Editor:
In their Perspective article, De Cock and El-Sadr (March 7 issue)1 highlight the need for data on when to start antiretroviral therapy (ART) for HIV-infected people in Africa who have CD4+ counts above 350 cells per cubic millimeter. However, their proposed solution — a new randomized, controlled trial in Africa — is flawed
Tree-based Coarsening and Partitioning of Complex Networks
Many applications produce massive complex networks whose analysis would
benefit from parallel processing. Parallel algorithms, in turn, often require a
suitable network partition. For solving optimization tasks such as graph
partitioning on large networks, multilevel methods are preferred in practice.
Yet, complex networks pose challenges to established multilevel algorithms, in
particular to their coarsening phase.
One way to specify a (recursive) coarsening of a graph is to rate its edges
and then contract the edges as prioritized by the rating. In this paper we (i)
define weights for the edges of a network that express the edges' importance
for connectivity, (ii) compute a minimum weight spanning tree with
respect to these weights, and (iii) rate the network edges based on the
conductance values of 's fundamental cuts. To this end, we also (iv)
develop the first optimal linear-time algorithm to compute the conductance
values of \emph{all} fundamental cuts of a given spanning tree. We integrate
the new edge rating into a leading multilevel graph partitioner and equip the
latter with a new greedy postprocessing for optimizing the maximum
communication volume (MCV). Experiments on bipartitioning frequently used
benchmark networks show that the postprocessing already reduces MCV by 11.3%.
Our new edge rating further reduces MCV by 10.3% compared to the previously
best rating with the postprocessing in place for both ratings. In total, with a
modest increase in running time, our new approach reduces the MCV of complex
network partitions by 20.4%
Searching for a link between the magnetic nature and other observed properties of Herbig Ae/Be stars and stars with debris disks
Among the 21 Herbig Ae/Be stars studied, new detections of a magnetic field
were achieved in six stars. For three Herbig Ae/Be stars, we confirm previous
magnetic field detections. The largest longitudinal magnetic field, =
-454+-42G, was detected in the Herbig Ae/Be star HD101412 using hydrogen lines.
No field detection at a significance level of 3sigma was achieved in stars with
debris disks. Our study does not indicate any correlation of the strength of
the longitudinal magnetic field with disk orientation, disk geometry, or the
presence of a companion. We also do not see any simple dependence on the
mass-accretion rate. However, it is likely that the range of observed field
values qualitatively supports the expectations from magnetospheric accretion
models giving support for dipole-like field geometries. Both the magnetic field
strength and the X-ray emission show hints for a decline with age in the range
of ~2-14Myrs probed by our sample supporting a dynamo mechanism that decays
with age. However, our study of rotation does not show any obvious trend of the
strength of the longitudinal magnetic field with rotation period. Furthermore,
the stars seem to obey the universal power-law relation between magnetic flux
and X-ray luminosity established for the Sun and main-sequence active dwarf
stars.Comment: 21 pages, 16 figures, 7 tables, accepted for publication in A&
Barrett's oesophagus: Epidemiology, cancer risk and implications for management
Although endoscopic surveillance of patients with Barrett's oesophagus has been widely implemented, its effectiveness is debateable. The recently reported low annual oesophageal adenocarcinoma risk in population studies, the failure to identify most Barrett's patients at risk of disease progression, the poor adherence to surveillance and biopsy protocols, and the significant risk of misclassification of dysplasia all tend to undermine the effectiveness of current management, in particular, endoscopic surveillance programmes, to prevent or improve the outcomes of patients with oesophageal adenocarcinoma. The ongoing increase in incidence of Barrett's oesophagus and consequent growth of the surveillance population, together with the associated discomfort and costs of endoscopic surveillance, demand improved techniques for accurately determining individual risk of oesophageal adenocarcinoma. More accurate techniques are needed to run efficient surveillance programmes in the coming decades. In this review, we will discuss the current knowledge on the epidemiology of Barrett's oesophagus, and the challenging epidemiological dilemmas that need to be addressed when a
HST/NICMOS2 coronagraphic observations of the circumstellar environment of three old PMS stars: HD 100546, SAO 206462 and MWC 480
The close environment of four old Pre-Main Sequence stars has been observed
thanks to the coronagraphic mode of the HST/NICMOS2 camera at lambda=1.6
micron. In the course of this program, the detection of a circumstellar annulus
around HD 141569 has already been presented in Augereau et al.(1999b). In this
paper, we report the detection of an elliptical structure around the Herbig Be
star HD 100546 extending from the very close edge of the coronagraphic mask
(~50 AU) to 350-380 AU (3.5-3.8 arcsec) from the star. The axis ratio gives a
disk inclination of 51+/-3 degrees to the line-of-sight and a position angle of
161+/-5 degrees, measured east of north. At 50 AU, the disk has a surface
brightness between 10.5 and 11 mag/arcsec^2, then follows a -2.92+/-0.04 radial
power law up to 250-270 AU and finally falls as r^{-5.5+/-0.2}. The inferred
optical thickness suggests that the disk is at least marginally optically thick
inside 80 AU and optically thin further out. Combined with anisotropic
scattering properties, this could explain the shape of a brightness asymmetry
observed along the minor axis of the disk. This asymmetry needs to be
confirmed. The circumstellar disks around SAO 206462 and MWC 480 are not
resolved, leading to constraints on the dust distribution. A tight binary
system separated by only 0.32+/-0.04 arcsec is nevertheless detected in the
close vicinity of SAO 206462.Comment: 13 pages, accepted for publication in Astronomy & Astrophysic
- …