203 research outputs found
The Design and Implementation of a Bayesian CAD Modeler for Robotic Applications
We present a Bayesian CAD modeler for robotic applications. We address the problem of taking into account the propagation of geometric uncertainties when solving inverse geometric problems. The proposed method may be seen as a generalization of constraint-based approaches in which we explicitly model geometric uncertainties. Using our methodology, a geometric constraint is expressed as a probability distribution on the system parameters and the sensor measurements, instead of a simple equality or inequality. To solve geometric problems in this framework, we propose an original resolution method able to adapt to problem complexity.
Using two examples, we show how to apply our approach by providing simulation results using our modeler
A Robotic CAD System using a Bayesian Framework
We present in this paper a Bayesian CAD system
for robotic applications. We address the problem of the
propagation of geometric uncertainties and how esian
CAD system for robotic applications. We address the
problem of the propagation of geometric uncertainties
and how to take this propagation into account when
solving inverse problems. We describe the methodology
we use to represent and handle uncertainties using
probability distributions on the system's parameters
and sensor measurements. It may be seen as a
generalization of constraint-based approaches where we
express a constraint as a probability distribution instead
of a simple equality or inequality. Appropriate
numerical algorithms used to apply this methodology
are also described. Using an example, we show how
to apply our approach by providing simulation results
using our CAD system
The importance of inversion disorder in the visible light induced persistent luminescence in Cr doped ABO (A = Zn or Mg and B = Ga or Al)
Cr doped spinel compounds ABO with A=Zn, Mg and B=Ga, Al
exhibit a long near infrared persistent luminescence when excited with UV or
X-rays. In addition, persistent luminescence of ZnGaO and to a lesser
extent MgGaO, can also be induced by visible light excitation via
A T transition of Cr, which makes these
compounds suitable as biomarkers for in vivo optical imaging of small animals.
We correlate this peculiar optical property with the presence of antisite
defects, which are present in ZnGaO and MgGaO. By using X-ray
absorption fine structure (XAFS) spectroscopy, associated with electron
paramagnetic resonance (EPR) and optical emission spectroscopy, it is shown
that an increase in antisite defects concentration results in a decrease in the
Cr-O bond length and the octahedral crystal field energy. A part of the defects
are in the close environment of Cr ions, as shown by the increasing
strain broadening of EPR and XAFS peaks observed upon increasing antisite
disorder. It appears that ZnAlO, which exhibits the largest crystal
field splitting of Cr and the smallest antisite disorder, does not show
considerable persistent luminescence upon visible light excitation as compared
to ZnGaO and MgGaO. These results highlight the importance of
Cr ions with neighboring antisite defects in the mechanism of persistent
luminescence exhibited by Cr doped ABO spinel compounds.Comment: 10 pages + supplementary (available on request
Domain k-Wise Consistency Made as Simple as Generalized Arc Consistency
Abstract. In Constraint Programming (CP), Generalized Arc Consistency (GAC) is the central property used for making inferences when solving Constraint Satisfaction Problems (CSPs). Developing simple and practical filtering algorithms based on consistencies stronger than GAC is a challenge for the CP community. In this paper, we propose to combine k-Wise Consistency (kWC) with GAC, where kWC states that every tuple in a constraint can be extended to every set of k − 1 additional constraints. Our contribution is as follows. First, we derive a domain-filtering consistency, called Domain k-Wise Consistency (DkWC), from the combination of kWC and GAC. Roughly speaking, this property corresponds to the pruning of values of GAC, when enforced on a CSP previously made kWC. Second, we propose a procedure to enforce DkWC, relying on an encoding of kWC to generate a modified CSP called k-interleaved CSP. Formally, we prove that enforcing GAC on the k-interleaved CSP corresponds to enforcing DkWC on the initial CSP. Consequently, we show that the strong DkWC can be enforced very easily in constraint solvers since the k-interleaved CSP is rather immediate to generate and only existing GAC propagators are required: in a nutshell, DkWC is made as simple and practical as GAC. Our experimental results show the benefits of our approach on a variety of benchmarks.
A distributed optimization method for the geographically distributed data centres problem
The geographically distributed data centres problem (GDDC) is a naturally distributed resource allocation problem. The problem involves allocating a set of virtual machines (VM) amongst the data centres (DC) in each time period of an operating horizon. The goal is to optimize the allocation of workload across a set of DCs such that the energy cost is minimized, while respecting limitations on data centre capacities, migrations of VMs, etc. In this paper, we propose a distributed optimization method for GDDC using the distributed constraint optimization (DCOP) framework. First, we develop a new model of the GDDC as a DCOP where each DC operator is represented by an agent. Secondly, since traditional DCOP approaches are unsuited to these types of large-scale problem with multiple variables per agent and global constraints, we introduce a novel semi-asynchronous distributed algorithm for solving such DCOPs. Preliminary results illustrate the benefits of the new method
Consistency Checking for the Evolution of Cardinality-based Feature Models
International audienceFeature models (FMs) are a widely used approach to specify the commonalities and variability in variable systems and software product lines. Various works have addressed edits to FMs for FM evolution and tool support to ensure consistency of FMs. An important extension to FMs are feature cardinalities and related constraints, as extensively used e.g., when modeling variability of cloud computing environments. Since cardinality-based FMs pose additional complexity, additional support for evolution and consistency checking with respect to feature cardinalities would be desirable, but has not been addressed yet. In this paper, we discuss common cardinality-based FM edits and resulting inconsistencies based on experiences with FMs in cloud domain. We introduce tool-support for automated inconsistency detection and explanation based on an off-the-shelf solver. We demonstrate the feasibility of the approach by an empirical evaluation showing the performance of the tool
Global Inverse Consistency for Interactive Constraint Satisfaction
International audienceSome applications require the interactive resolution of a constraint problem by a human user. In such cases, it is highly desirable that the person who interactively solves the problem is not given the choice to select values that do not lead to solutions. We call this property global inverse consistency. Existing systems simulate this either by maintaining arc consistency after each assignment performed by the user or by compiling offline the problem as a multi-valued decision diagram. In this paper, we define several questions related to global inverse consistency and analyse their complexity. Despite their theoretical intractability, we propose several algorithms for enforcing global inverse consistency and we show that the best version is efficient enough to be used in an interactive setting on several configuration and design problems. We finally extend our contribution to the inverse consistency of tuples
Investigating the impact of quasar-driven outflows on galaxies at redshift 0.3-0.4
We present a detailed study of the kinematics of 19 QSO2s in the range
0.3 10^{8.5}_{\odot}\lambda\r{A}_{OF}_{\odot}\pm_{OF}\pm_{\odot}^{-1}_{kin}\pm^{-1}\pm_{\odot}^{-1}\pm^{-1}$). We do not find any significant
correlation between the outflow properties and the previously mentioned galaxy
properties.
4 out of 5 QSO2s without a YS<100 Myr show highly disturbed kinematics,
whereas only 5 out of the 14 QSO2s with YSPs show similarly asymmetric [OIII]
profiles. This might be indicative of negative feedback. The lack of
correlation between the outflow properties and the presence of mergers in
different interaction stages might be due to their different dynamical
timescales. Lastly, the small radio luminosity range covered by our sample may
be impeding the detection of any correlation between radio emission and outflow
properties.Comment: 26 pages, 9 figures. Accepted for publication in A&
Jet-driven outflows of ionized gas in the nearby radio galaxy 3C 293
Fast outflows of gas, driven by the interaction between the radio jets and interstellar medium
(ISM) of the host galaxy, are being observed in an increasing number of galaxies. One such
example is the nearby radio galaxy 3C 293. In this paper we present integral field unit
observations taken with OASIS on the William Herschel Telescope, enabling us to map the
spatial extent of the ionized gas outflows across the central regions of the galaxy. The jet-driven
outflow in 3C 293 is detected along the inner radio lobes with a mass outflow rate ranging
from ∼0.05 to 0.17 M yr−1 (in ionized gas) and corresponding kinetic power of ∼0.5–
3.5 × 1040 erg s−1. Investigating the kinematics of the gas surrounding the radio jets (i.e. not
directly associated with the outflow), we find linewidths broader than 300 km s−1 up to 5 kpc in
the radial direction from the nucleus (corresponding to 3.5 kpc in the direction perpendicular to
the radio axis at maximum extent). Along the axis of the radio jet linewidths >400 km s−1 are
detected out to 7 kpc from the nucleus and linewidths of >500 km s−1 at a distance of 12 kpc
from the nucleus, indicating that the disturbed kinematics clearly extend well beyond the high
surface brightness radio structures of the jets. This is suggestive of the cocoon structure seen
in simulations of jet–ISM interaction and implies that the radio jets are capable of disturbing
the gas throughout the central regions of the host galaxy in all directions
Investigating the impact of quasar-driven outflows on galaxies at z ∼ 0.3–0.4
Aims. We present a detailed study of the kinematics of 19 type 2 quasars (QSO2s) with redshifts in the range 0.3  108.5 L⊙. We aim to advance our understanding of the active galactic nucleus (AGN) feedback phenomenon by correlating outflow properties with (i) young stellar populations (YSPs) with ages < 100 Myr, (ii) the optical morphology and the environment of the galaxies, and (iii) the radio luminosity.
Methods. We characterized the ionized gas kinematics using the [OIII]λ5007 Å emission line profiles detected in intermediate spectral resolution (R ∼ 1500–2500) optical spectra of the QSO2s. To do this, we employed three different outflow detection methods: multicomponent parametric, flux-weighted nonparametric, and peak-weighted nonparametric.
Results. We detect ionized outflows in 18 of the 19 QSO2s using the parametric analysis, and in all of them using the nonparametric methods. We find higher outflow masses using the parametric analysis (average log MOF(M⊙) = 6.47  ±  0.50), and higher mass rates and kinetic powers with the flux-weighted nonparametric method (MOF = 4.0  ±  4.4 M⊙ yr−1 and Ekin = 41.9  ±  0.6 erg s−1). However, when we use the parametric method and the maximum outflow velocities (vmax), we measure the highest outflow mass rates and kinetic energies (MOF = 23  ±  35 M⊙ yr−1 and log(Ekin) = 42.9  ±  0.6 erg s−1). We do not find any significant correlation between the outflow properties and the previously mentioned AGN and galaxy-wide properties.
Conclusions. Four of the five QSO2s without a YSP of age < 100 Myr show highly disturbed kinematics, whereas only 5 out of the 14 QSO2s with YSPs show similarly asymmetric [OIII] profiles. Despite the small sample size, this might be indicative of negative feedback. The lack of a correlation between the outflow properties and the galaxies optical morphologies might be due to their different dynamical timescales (millions of years in the case of the outflows versus billions of years in the case of galaxy mergers). Last, the small radio luminosity range covered by our sample, log(L5 GHz) = [22.1, 24.7] W Hz−1, may impede the detection of any correlation between radio emission and outflow properties
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