12,286 research outputs found
Learning Manipulation under Physics Constraints with Visual Perception
Understanding physical phenomena is a key competence that enables humans and animals to act and interact under uncertain perception in previously unseen environments containing novel objects and their configurations. In this work, we consider the problem of autonomous block stacking and explore solutions to learning manipulation under physics constraints with visual perception inherent to the task. Inspired by the intuitive physics in humans, we first present an end-to-end learning-based approach to predict stability directly from appearance, contrasting a more traditional model-based approach with explicit 3D representations and physical simulation. We study the model's behavior together with an accompanied human subject test. It is then integrated into a real-world robotic system to guide the placement of a single wood block into the scene without collapsing existing tower structure. To further automate the process of consecutive blocks stacking, we present an alternative approach where the model learns the physics constraint through the interaction with the environment, bypassing the dedicated physics learning as in the former part of this work. In particular, we are interested in the type of tasks that require the agent to reach a given goal state that may be different for every new trial. Thereby we propose a deep reinforcement learning framework that learns policies for stacking tasks which are parametrized by a target structure
The evolution of the number density of compact galaxies
We compare the number density of compact (small size) massive galaxies at low
and high redshift using our Padova Millennium Galaxy and Group Catalogue
(PM2GC) at z=0.03-0.11 and the CANDELS results from Barro et al. (2013) at
z=1-2. The number density of local compact galaxies with luminosity weighted
(LW) ages compatible with being already passive at high redshift is compared
with the density of compact passive galaxies observed at high-z. Our results
place an upper limit of a factor ~2 to the evolution of the number density and
are inconsistent with a significant size evolution for most of the compact
galaxies observed at high-z. The evolution may be instead significant (up to a
factor 5) for the most extreme, ultracompact galaxies. Considering all compact
galaxies, regardless of LW age and star formation activity, a minority of local
compact galaxies (<=1/3) might have formed at z<1. Finally, we show that the
secular decrease of the galaxy stellar mass due to simple stellar evolution may
in some cases be a non-negligible factor in the context of the evolution of the
mass-size relation, and we caution that passive evolution in mass should be
taken into account when comparing samples at different redshifts.Comment: ApJ in pres
Transport Properties of a Chain of Anharmonic Oscillators with random flip of velocities
We consider the stationary states of a chain of anharmonic coupled
oscillators, whose deterministic hamiltonian dynamics is perturbed by random
independent sign change of the velocities (a random mechanism that conserve
energy). The extremities are coupled to thermostats at different temperature
and and subject to constant forces and . If
the forces differ the center of mass of the system will
move of a speed inducing a tension gradient inside the system. Our aim is
to see the influence of the tension gradient on the thermal conductivity. We
investigate the entropy production properties of the stationary states, and we
prove the existence of the Onsager matrix defined by Green-kubo formulas
(linear response). We also prove some explicit bounds on the thermal
conductivity, depending on the temperature.Comment: Published version: J Stat Phys (2011) 145:1224-1255 DOI
10.1007/s10955-011-0385-
The Clinical Approach to Successful Program Development
To more adequately meet the needs for the decade ahead, it is essential that sociology departments evaluate their existing curricula and plan new programs or concentrations that will interest and attract students. Using the example of clinical sociology, this article focuses on general guidelines for developing a variety of program models in sociological practice. The guidelines are divided into the three parts of assessment, planning, and implementation, and an inventory of ideas and suggestions are given for each phase. Relevant issues of the importance of labels, leadership and independence, and rationales for program development are discussed
An entropic approach to local realism and noncontextuality
For any Bell locality scenario (or Kochen-Specker noncontextuality scenario),
the joint Shannon entropies of local (or noncontextual) models define a convex
cone for which the non-trivial facets are tight entropic Bell (or
contextuality) inequalities. In this paper we explore this entropic approach
and derive tight entropic inequalities for various scenarios. One advantage of
entropic inequalities is that they easily adapt to situations like bilocality
scenarios, which have additional independence requirements that are non-linear
on the level of probabilities, but linear on the level of entropies. Another
advantage is that, despite the nonlinearity, taking detection inefficiencies
into account turns out to be very simple. When joint measurements are conducted
by a single detector only, the detector efficiency for witnessing quantum
contextuality can be arbitrarily low.Comment: 12 pages, 8 figures, minor mistakes correcte
The Clinical Approach to Successful Program Development
To more adequately meet the needs for the decade ahead, it is essential that sociology departments evaluate their existing curricula and plan new programs or concentrations that will interest and attract students. Using the example of clinical sociology, this article focuses on general guidelines for developing a variety of program models in sociological practice. The guidelines are divided into the three parts of assessment, planning, and implementation, and an inventory of ideas and suggestions are given for each phase. Relevant issues of the importance of labels, leadership and independence, and rationales for program development are discussed
Optimization conditions of UV-C radiation combined with ultrasound-assisted extraction of cherry tomato (Lycopersicon esculentum) lycopene extract
The aim of this work was to study the effect of UV-C radiation on ultrasound assisted extraction
(UAE) of cherry tomato bioactive compounds. Cherry tomatoes were exposed to two UV-C radiation
doses (0.5 and 1.0 J cmâ2
) and stored at 20 ± 0.5 oC for 7 days. Next, they were lyophilized, and
the bioactive compounds were extracted by UAE at 20 KHz. To evaluate the effectiveness of the
extraction process of the bioactive compounds, a CCRD (central composite rotational design) was
used together with RSM (response surface methodology), for extraction times from 4 to 12 minutes
and concentrations (g of lyophilized product / L of ethanol) of 1:10, 1:20 and 1:30. The extracts
obtained from the irradiated tomatoes presented 5.8 times more lycopene content than the controls
and higher antioxidant activity was obtained for 4 and 8 min, in the concentrations 1:10 and 1:20 (m
vâ1). Through numerical model optimization, optimal extraction conditions were obtained. The results
demonstrated that by previously irradiating tomatoes with UV-C light, the UAE yielded considerably
higher amounts of lycopene and other bioactives.CNPq (National Council of Technological and Scientific
Development, Brazil), Erasmus Mundus action 2; Fellow
Mundus Project; Department of Chemical Engineering and Food Engineering
(UFSC - Brazil) and the Department of Food Engineering (UAlg - Portugal) .info:eu-repo/semantics/publishedVersio
Classical versus Quantum Time Evolution of Densities at Limited Phase-Space Resolution
We study the interrelations between the classical (Frobenius-Perron) and the
quantum (Husimi) propagator for phase-space (quasi-)probability densities in a
Hamiltonian system displaying a mix of regular and chaotic behavior. We focus
on common resonances of these operators which we determine by blurring
phase-space resolution. We demonstrate that classical and quantum time
evolution look alike if observed with a resolution much coarser than a Planck
cell and explain how this similarity arises for the propagators as well as
their spectra. The indistinguishability of blurred quantum and classical
evolution implies that classical resonances can conveniently be determined from
quantum mechanics and in turn become effective for decay rates of quantum
correlations.Comment: 10 pages, 3 figure
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