8,904 research outputs found
A probabilistic data-driven model for planar pushing
This paper presents a data-driven approach to model planar pushing
interaction to predict both the most likely outcome of a push and its expected
variability. The learned models rely on a variation of Gaussian processes with
input-dependent noise called Variational Heteroscedastic Gaussian processes
(VHGP) that capture the mean and variance of a stochastic function. We show
that we can learn accurate models that outperform analytical models after less
than 100 samples and saturate in performance with less than 1000 samples. We
validate the results against a collected dataset of repeated trajectories, and
use the learned models to study questions such as the nature of the variability
in pushing, and the validity of the quasi-static assumption.Comment: 8 pages, 11 figures, ICRA 201
Friction Variability in Planar Pushing Data: Anisotropic Friction and Data-collection Bias
Friction plays a key role in manipulating objects. Most of what we do with
our hands, and most of what robots do with their grippers, is based on the
ability to control frictional forces. This paper aims to better understand the
variability and predictability of planar friction. In particular, we focus on
the analysis of a recent dataset on planar pushing by Yu et al. [1] devised to
create a data-driven footprint of planar friction.
We show in this paper how we can explain a significant fraction of the
observed unconventional phenomena, e.g., stochasticity and multi-modality, by
combining the effects of material non-homogeneity, anisotropy of friction and
biases due to data collection dynamics, hinting that the variability is
explainable but inevitable in practice.
We introduce an anisotropic friction model and conduct simulation experiments
comparing with more standard isotropic friction models. The anisotropic
friction between object and supporting surface results in convergence of
initial condition during the automated data collection. Numerical results
confirm that the anisotropic friction model explains the bias in the dataset
and the apparent stochasticity in the outcome of a push. The fact that the data
collection process itself can originate biases in the collected datasets,
resulting in deterioration of trained models, calls attention to the data
collection dynamics.Comment: 8 pages, 13 figure
Leveraging Intermediate Artifacts to Improve Automated Trace Link Retrieval
Software traceability establishes a network of connections between diverse artifacts such as requirements, design, and code. However, given the cost and effort of creating and maintaining trace links manually, researchers have proposed automated approaches using information retrieval techniques. Current approaches focus almost entirely upon generating links between pairs of artifacts and have not leveraged the broader network of interconnected artifacts. In this paper we investigate the use of intermediate artifacts to enhance the accuracy of the generated trace links – focus- ing on paths consisting of source, target, and intermediate artifacts. We propose and evaluate combinations of techniques for computing semantic similarity, scaling scores across multiple paths, and aggregating results from multiple paths. We report results from five projects, including one large industrial project. We find that leverag- ing intermediate artifacts improves the accuracy of end-to-end trace retrieval across all datasets and accuracy metrics. After further analysis, we discover that leveraging intermediate artifacts is only helpful when a project’s artifacts share a common vocabulary, which tends to occur in refinement and decomposition hierarchies of artifacts. Given our hybrid approach that integrates both direct and transitive links, we observed little to no loss of accuracy when intermediate artifacts lacked a shared vocabulary with source or target artifacts
Faith in the Algorithm, Part 1: Beyond the Turing Test
Since the Turing test was first proposed by Alan Turing in 1950, the primary
goal of artificial intelligence has been predicated on the ability for
computers to imitate human behavior. However, the majority of uses for the
computer can be said to fall outside the domain of human abilities and it is
exactly outside of this domain where computers have demonstrated their greatest
contribution to intelligence. Another goal for artificial intelligence is one
that is not predicated on human mimicry, but instead, on human amplification.
This article surveys various systems that contribute to the advancement of
human and social intelligence
Simple model for a Quantum Wire II. Correlations
In a previous paper (Eur. Phys. J. B 30, 239-251 (2002)) we have presented
the main features and properties of a simple model which -in spite of its
simplicity- describes quite accurately the qualitative behaviour of a quantum
wire. The model was composed of N distinct deltas each one carrying a different
coupling. We were able to diagonalize the Hamiltonian in the periodic case and
yield a complete and analytic description of the subsequent band structure.
Furthermore the random case was also analyzed and we were able to describe
Anderson localization and fractal structure of the conductance. In the present
paper we go one step further and show how to introduce correlations among the
sites of the wire. The presence of a correlated disorder manifests itself by
altering the distribution of states and the localization of the electrons
within the systemComment: RevTex, 7 pages, 9 figures (3 greyscale, 6 coloured
Infinite chain of N different deltas: a simple model for a Quantum Wire
We present the exact diagonalization of the Schrodinger operator
corresponding to a periodic potential with N deltas of different couplings, for
arbitrary N. This basic structure can repeat itself an infinite number of
times. Calculations of band structure can be performed with a high degree of
accuracy for an infinite chain and of the correspondent eigenlevels in the case
of a random chain. The main physical motivation is to modelate quantum wire
band structure and the calculation of the associated density of states. These
quantities show the fundamental properties we expect for periodic structures
although for low energy the band gaps follow unpredictable patterns. In the
case of random chains we find Anderson localization; we analize also the role
of the eigenstates in the localization patterns and find clear signals of
fractality in the conductance. In spite of the simplicity of the model many of
the salient features expected in a quantum wire are well reproduced.Comment: 28 pages, LaTeX, 13 eps figures (3 color
Some stylized facts of returns in the foreign exchange and stock markets in Peru
Some stylized facts for foreign exchange and stock market returns are explored using statistical methods. Formal statistics for testing presence of autocorrelation, asymmetry, and other deviations from normality is applied to these financial returns. Dynamic correlations and different kernel estimations and approximations of the empirical distributions are also under scrutiny. Furthermore, dynamic analysis of mean, standard deviation, skewness and kurtosis are also performed to evaluate time-varying properties in return distributions. Main results reveal different sources and types of non-normality in the return distributions in both markets. Left fat tails, excess kurtosis, return clustering and unconditional time-varying moments show important deviations from normality. Identifiable volatility cycles in both forex and stock markets are associated to common macro financial uncertainty events.Non-Normal Distributions, Stock Market Returns, Foreign Exchange Market Returns.
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