280 research outputs found
Simulating Vocal Imitation in Infants, using a Growth Articulatory Model and Speech Robotics
In order to shed lights on the cognitive representations
likely to underlie early vocal imitation, we tried to simulate
Kuhl and Meltzoff's experiment (1996), using Bayesian
robotics and a statistical model of the vocal tract that had
been fitted to pre-babblers' actual vocalizations. It was
shown that audition is compulsory to account for infants'
early vocal imitation performance, inasmuch as the
simulation of purely visual imitation failed to reproduce
infants' score and pattern of imitation. Further, a small
number of vocalizations (less than 100!) appeared to be
enough for a learning process to provide scores at least as
high as those of pre-babblers. Thus, early vocal imitation
lies in the reach of a baby robot, with only a few
assumptions about learning and imitation
The Ariadne's Clew Algorithm
We present a new approach to path planning, called the "Ariadne's clew
algorithm". It is designed to find paths in high-dimensional continuous spaces
and applies to robots with many degrees of freedom in static, as well as
dynamic environments - ones where obstacles may move. The Ariadne's clew
algorithm comprises two sub-algorithms, called Search and Explore, applied in
an interleaved manner. Explore builds a representation of the accessible space
while Search looks for the target. Both are posed as optimization problems. We
describe a real implementation of the algorithm to plan paths for a six degrees
of freedom arm in a dynamic environment where another six degrees of freedom
arm is used as a moving obstacle. Experimental results show that a path is
found in about one second without any pre-processing
The Ariadne's Clew Algorithm
We present a new approach to path planning, called the ``Ariadne's clew algorithm''. It is designed to find paths in high-dimensional continuous spaces and applies to robots with many degrees of freedom in static, as well as dynamic environments --- ones where obstacles may move. The Ariadne's clew algorithm comprises two sub-algorithms, called SEARCH and EXPLORE, applied in an interleaved manner. EXPLORE builds a representation of the accessible space while SEARCH looks for the target. Both are posed as optimization problems. We describe a real implementation of the algorithm to plan paths for a six degrees of freedom arm in a dynamic environment where another six degrees of freedom arm is used as a moving obstacle. Experimental results show that a path is found in about one second without any pre-processing
A Framework for Decision-based Consistencies
International audienceConsistencies are properties of constraint networks that can be enforced by appropriate algorithms to reduce the size of the search space to be explored. Recently, many consistencies built upon taking decisions (most often, variable assignments) and stronger than (general- ized) arc consistency have been introduced. In this paper, our ambition is to present a clear picture of decision-based consistencies. We identify four general classes (or levels) of decision-based consistencies, denoted by S∆φ, E∆φ, B∆φ and D∆φ, study their relationships, and show that known consistencies are particular cases of these classes. Interestingly, this gen- eral framework provides us with a better insight into decision-based con- sistencies, and allows us to derive many new consistencies that can be directly integrated and compared with other ones
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.
The chemical ecology of seed dispersal in monoecious and dioecious figs
1In the nursery pollination system of figs (Ficus, Moraceae), flower-bearing receptacles called syconia breed pollinating wasps and are units of both pollination and seed dispersal. Pollinators and mammalian seed dispersers are attracted to syconia by volatile organic compounds (VOCs). In monoecious figs, syconia produce both wasps and seeds, while in (gyno)dioecious figs, male (gall) fig trees produce wasps and female (seed) fig trees produce seeds. 2 VOCs were collected using dynamic headspace adsorption methods on freshly collected figs from different trees using Super Q collection traps. VOC profiles were determined using gas chromatography-mass spectrometry (GC-MS). 3 The VOC profile of receptive and dispersal phase figs were clearly different only in the dioecious mammal-dispersed Ficus hispida but not in dioecious bird-dispersed F. exasperata and monoecious bird-dispersed F. tsjahela. 4 The VOC profile of dispersal phase female figs was clearly different from that of male figs only in F. hispida but not in F. exasperata, as predicted from the phenology of syconium production which only in F. hispida overlaps between male and female trees. Greater difference in VOC profile in F. hispida might ensure preferential removal of seed figs by dispersal agents when gall figs are simultaneously available. 5 The VOC profile of only mammal-dispersed female figs of F. hispida had high levels of fatty acid derivatives such as amyl-acetates and 2-heptanone, while monoterpenes, sesquiterpenes and shikimic acid derivatives were predominant in the other syconial types. A bird- and mammal-repellent compound methyl anthranilate occurred only in gall figs of both dioecious species, as expected, since gall figs containing wasp pollinators should not be consumed by dispersal agents
Constituents of Kawal, fermented Cassia obtusifolia leaves, a traditional food from Chad
Femented leaves of Cassia obtusifolia are used as a substitute of meat or an appetizing agent by people of eastern of Chad and south of Sudan. Chemical composition of the methylene chloride extract from the fermented leaves of this legume was analyzed for the first time by GC and GC/MC. Thirty threeconstituents were identified. The major components are found to be aliphatic acids and identified as hexanoic acid (27%), butyric acid (10.4%) and valeric acid (6.3%) with lesser amounts of p-ethylphenol (17.2%) and p-methylphenol (13%). Examination of the protein fraction from leaves indicated 20.2% inthe crude leaves and 12.9% in the fermented leaves. The participation of 10 g of fermented C. obtusifolia leaves to the daily requirements in essential amino acids of an adult is from 13 to 25% of needed amount. Moreover this traditional food had a high content of potassium and calcium
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&
Conjunctions of Among Constraints
Many existing global constraints can be encoded as a conjunction of among
constraints. An among constraint holds if the number of the variables in its
scope whose value belongs to a prespecified set, which we call its range, is
within some given bounds. It is known that domain filtering algorithms can
benefit from reasoning about the interaction of among constraints so that
values can be filtered out taking into consideration several among constraints
simultaneously. The present pa- per embarks into a systematic investigation on
the circumstances under which it is possible to obtain efficient and complete
domain filtering algorithms for conjunctions of among constraints. We start by
observing that restrictions on both the scope and the range of the among
constraints are necessary to obtain meaningful results. Then, we derive a
domain flow-based filtering algorithm and present several applications. In
particular, it is shown that the algorithm unifies and generalizes several
previous existing results.Comment: 15 pages plus appendi
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