3,948 research outputs found
Structured light techniques for 3D surface reconstruction in robotic tasks
Robotic tasks such as navigation and path planning can be greatly enhanced by a vision system capable of providing depth perception from fast and accurate 3D surface reconstruction. Focused on robotic welding tasks we present a comparative analysis of a novel mathematical formulation for 3D surface reconstruction and discuss image processing requirements for reliable detection of patterns in the image. Models are presented for a parallel and angled configurations of light source and image sensor. It is shown that the parallel arrangement requires 35\% fewer arithmetic operations to compute a point cloud in 3D being thus more appropriate for real-time applications. Experiments show that the technique is appropriate to scan a variety of surfaces and, in particular, the intended metallic parts for robotic welding tasks
Hierarchical Residual Learning Based Vector Quantized Variational Autoencoder for Image Reconstruction and Generation
We propose a multi-layer variational autoencoder method, we call HR-VQVAE, that learns hierarchical discrete representations of the data. By utilizing a novel objective function, each layer in HR-VQVAE learns a discrete representation of the residual from previous layers through a vector quantized encoder. Furthermore, the representations at each layer are hierarchically linked to those at previous layers. We evaluate our method on the tasks of image reconstruction and generation. Experimental results demonstrate that the discrete representations learned by HR-VQVAE enable the decoder to reconstruct high-quality images with less distortion than the baseline methods, namely VQVAE and VQVAE-2. HR-VQVAE can also generate high-quality and diverse images that outperform state-of-the-art generative models, providing further verification of the efficiency of the learned representations. The hierarchical nature of HR-VQVAE i) reduces the decoding search time, making the method particularly suitable for high-load tasks and ii) allows to increase the codebook size without incurring the codebook collapse problem
The relationship between seismic deformation and deep seated gravitational
This paper re-evaluates the origin of some peculiar patterns of ground deformation observed by
space geodetic techniques during the two earthquakes of September 26th of the Colfiorito seismic
sequence. The surface displacement field due to the fault dislocation, as modeled with the classic
Okada elastic formulations, shows some areas with high residuals which cannot be attributed to
unsimulated model complexities. The latter was investigated using geomorphological analysis, by
recognising the geologic evidence of deep seated gravitational slope deformations (DSGSD) of the
block-slide type. The shape and direction of the co-seismic ground displacement observed in these
areas are correlated with the expected pattern of movement produced by the reactivation of the
identified DSGSD. At least a few centimetres of negative Line of Sight ground displacement was
determined for the Costa Picchio, Mt. Pennino, and Mt. Prefoglio areas. A considerable horizontal
component of movement in the Costa Picchio DSGSD is evident from a qualitative analysis of
ascending and descending interferograms. The timing of the geodetic data indicates that the ground
movement occurred during the seismic shaking, and that it did not progress appreciably during the
following months. In this work it has been verified the seismic triggering of DSGSD previously
hypothesized by many authors. A further implication is that in the assessment of DSGSD hazard it is
necessary to consider the seismic input as an important cause of acceleration of the deformation rates
The origin of the Fe K features in Markarian 205 and Markarian 509
We examine the 3-10 keV EPIC spectra of Mrk 205 and Mrk 509 to investigate
their Fe K features. The most significant feature in the spectra of both
objects is an emission line at 6.4 keV. The spectra can be adequately modelled
with a power law and a relatively narrow (sigma < 0.2 keV) Fe K alpha emission
line. Better fits are obtained when an additional Gaussian emission line,
relativistic accretion-disk line, or Compton reflection from cold material, is
added to the spectral model. We obtain similar goodness of fit for any of these
three models, but the model including Compton reflection from cold material
offers the simplest, physically self-consistent solution, because it only
requires one reprocessing region. Thus the Fe K spectral features in Mrk 205
and Mrk 509 do not present strong evidence for reprocessing in the inner,
relativistic parts of accretion disks.Comment: accepted for publication in MNRA
Thermoelectric and microbattery hybrid system with its power management
Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/handle/2042/5920)International audienceIntegration of a power source with a MEMS to obtain an autonomous or remote system is a very challenging task. Such a device is currently being developed. It consists in hybriding an energy storage system (thin film solid state battery) with a scavenging energy system (thermogenerator) in a very small volume. It requires also power management to both control charge of the battery by the thermogenerator and discharge of the battery by the load, i.e. a sensor for instance
Dynamic changes in synaptic plasticity genes in ipsilateral and contralateral inferior colliculus following unilateral noise-induced hearing loss
Unilateral noise-induced hearing loss reduces the input to the central auditory pathway disrupting the excitatory and inhibitory inputs to the inferior colliculus (IC), an important binaural processing center. Little is known about the compensatory synaptic changes that occur in the IC as a consequence of unilateral noise-induced hearing loss. To address this issue, Sprague–Dawley rats underwent unilateral noise exposure resulting in severe unilateral hearing loss. IC tissues from the contralateral and ipsilateral IC were evaluated for acute (2-d) and chronic (28-d) changes in the expression of 84 synaptic plasticity genes on a PCR array. Arc and Egr1 genes were further visualized by in situ hybridization to validate the PCR results. None of the genes were upregulated, but many were downregulated post-exposure. At 2-d post-exposure, more than 75% of the genes were significantly downregulated in the contralateral IC, while only two were downregulated in the ipsilateral IC. Many of the downregulated genes were related to long-term depression, long-term potentiation, cell adhesion, immediate early genes, neural receptors and postsynaptic density. At 28-d post-exposure, the gene expression pattern was reversed with more than 85% of genes in the ipsilateral IC now downregulated. Most genes previously downregulated in the contralateral IC 2-d post-exposure had recovered; less than 15% remained downregulated. These time-dependent, asymmetric changes in synaptic plasticity gene expression could shed new light on the perceptual deficits associated with unilateral hearing loss and the dynamic structural and functional changes that occur in the IC days and months following unilateral noise-induced hearing loss
The August 17, 1999 Izmit, Turkey, earthquake: slip distribution from dislocation modeling of DInSAR and surface offset
We show the results of application of Differential SAR Interferometry to the MW 7.4, August 17, 1999, Izmit
earthquake, Western Turkey. The differential interferogram is obtained using an interferometric ERS2 ascending
pair with a time interval of 35 days (August 13th - September 17th). The fringe pattern clearly defines the coseismic
displacement field extended in an area of about 100 km N-S and 120 km E-W. The analysis of the interferogram
shows the right-lateral strike-slip movement on the activated section of the North Anatolian fault system. The
maximum SAR-detected displacement ranges between 117.6 cm and 134.4 cm in the proximity of Gölcük. We
invert SAR data for uniform dislocation on a single fault plane using a Montecarlo procedure, with the aim of
testing a large set of a priori possible asperity distributions on the fault. We then use a forward modeling approach
to evaluate the slip variability for the dislocation using additional constraints as surface offsets and seismicity
distribution: in this case we allow unit cells to undergo different values of slip in order to refine the initial dislocation
model. Misfits between SAR data and modeled slant range displacements are generally low for all our models
(~ 12 cm). Our results indicate that slip is concentrated in the central-western part of the fault, in the upper 10-15
km, tapering to the fault tips. For the Izmit case, we note that a well constrained fault model can be obtained only
integrating DInSAR data with additional observations. This is mainly due to an undersampling of the displacement
field by DInSAR, caused by decorrelation and lack of image data
Multiple carcasses of Olive Ridleys along Malvan Beach
The Olive Ridley turtle (Lepidochelys olivacea) is protected under the Indian Wildlife (Protection) Act, 1972. Maharashtra government along with NGOs are undertaking several efforts in conservation of sea turtles along the coast. There is a state sponsored incentive program of `500 for locating and sharing information with forest officials. Malvan coast in Sindhudurg district of Maharashtra is known for turtle and fisheries interactions. Occasional turtle nestings can be seen between November to April
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