6,793 research outputs found

    Noise-induced phase transitions: Effects of the noises' statistics and spectrum

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    The local, uncorrelated multiplicative noises driving a second-order, purely noise-induced, ordering phase transition (NIPT) were assumed to be Gaussian and white in the model of [Phys. Rev. Lett. \textbf{73}, 3395 (1994)]. The potential scientific and technological interest of this phenomenon calls for a study of the effects of the noises' statistics and spectrum. This task is facilitated if these noises are dynamically generated by means of stochastic differential equations (SDE) driven by white noises. One such case is that of Ornstein--Uhlenbeck noises which are stationary, with Gaussian pdf and a variance reduced by the self-correlation time (\tau), and whose effect on the NIPT phase diagram has been studied some time ago. Another such case is when the stationary pdf is a (colored) Tsallis' (q)--\emph{Gaussian} which, being a \emph{fat-tail} distribution for (q>1) and a \emph{compact-support} one for (q<1), allows for a controlled exploration of the effects of the departure from Gaussian statistics. As done before with stochastic resonance and other phenomena, we now exploit this tool to study--within a simple mean-field approximation and with an emphasis on the \emph{order parameter} and the ``\emph{susceptibility}''--the combined effect on NIPT of the noises' statistics and spectrum. Even for relatively small (\tau), it is shown that whereas fat-tail noise distributions ((q>1)) counteract the effect of self-correlation, compact-support ones ((q<1)) enhance it. Also, an interesting effect on the susceptibility is seen in the last case.Comment: 6 pages, 10 figures, uses aipproc.cls, aip-8s.clo and aipxfm.sty. To appear in AIP Conference Proceedings. Invited talk at MEDYFINOL'06 (XV Conference on Nonequilibrium Statistical Mechanics and Nonlinear Physics

    Pile Performance Assessment under Induced Lateral Loading

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    This research work focuses on determining the internal force distribution in piles from displacement measurements when the piles no longer behave fully elastically. The method is based on the principle of virtual work (unit-load method) and allows the calculation of the bending moment distribution along piles, which is assumed to be the dominant internal force in bending. Four recent case studies were used, focusing either on liquefaction induced loading or on static induced plasticity. Comparison between the observed and calculated bending moments highlighted the method’s flexibility to derive accurate results in various soil conditions, length-size of experiment and load conditions. The method is also equally applicable to piles and to retaining walls. The maximum error between observed and calculated maximum bending moment ranged from 30% to less than 5% whereas the location of the maximum bending moment along the length of the pile was successfully calculated in all tests which stands promising for prediction of plastic hinges. The method can be used as a reliable-rapid tool to estimate the pile state following earthquake loading. This, in turn, can be used as a resilient and vulnerability indicator of the pile ability to resist further loading and continue to perform its function safely

    Thermal 3D modelling

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    This paper presents the case of 3D reconstructing an object using infrared imagery. Conversely to previous solutions that used the RGB imagery to make the 3D reconstruction and later superimpose the infrared, this paper makes use of the infrared imagery directly. The results of the reconstruction are then compared to an accurate laser scan of the object which provides a ground-truth. The results show that although it is still inaccurate this is mainly due to the low resolution of thermal imagery rather than their direct application for reconstruction

    Alice falls into a black hole: Entanglement in non-inertial frames

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    Two observers determine the entanglement between two free bosonic modes by each detecting one of the modes and observing the correlations between their measurements. We show that a state which is maximally entangled in an inertial frame becomes less entangled if the observers are relatively accelerated. This phenomenon, which is a consequence of the Unruh effect, shows that entanglement is an observer-dependent quantity in non-inertial frames. In the high acceleration limit, our results can be applied to a non-accelerated observer falling into a black hole while the accelerated one barely escapes. If the observer escapes with infinite acceleration, the state's distillable entanglement vanishes.Comment: I.F-S published before with maiden name Fuentes-Guridi Replaced with published version. Phys. Rev. Lett. in pres

    Berry Phase Quantum Thermometer

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    We show how Berry phase can be used to construct an ultra-high precision quantum thermometer. An important advantage of our scheme is that there is no need for the thermometer to acquire thermal equilibrium with the sample. This reduces measurement times and avoids precision limitations.Comment: Updated to published version. I. Fuentes previously published as I. Fuentes-Guridi and I. Fuentes-Schulle

    An improved robot for bridge inspection

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    This paper presents a significant improvement from the previous submission from the same authors at ISARC 2016. The robot is now equipped with low-cost cameras and a 2D laser scanner which is used to monitor and survey a bridge bearing. The robot is capable of localising by combining a data from a pre-surveyed 3D model of the space with real-time data collection in-situ. Autonomous navigation is also performed using the 2D laser scanner in a mapped environment. The Robot Operating System (ROS) framework is used to integrate data collection and communication for navigation

    ViTac: Feature Sharing between Vision and Tactile Sensing for Cloth Texture Recognition

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    Vision and touch are two of the important sensing modalities for humans and they offer complementary information for sensing the environment. Robots could also benefit from such multi-modal sensing ability. In this paper, addressing for the first time (to the best of our knowledge) texture recognition from tactile images and vision, we propose a new fusion method named Deep Maximum Covariance Analysis (DMCA) to learn a joint latent space for sharing features through vision and tactile sensing. The features of camera images and tactile data acquired from a GelSight sensor are learned by deep neural networks. But the learned features are of a high dimensionality and are redundant due to the differences between the two sensing modalities, which deteriorates the perception performance. To address this, the learned features are paired using maximum covariance analysis. Results of the algorithm on a newly collected dataset of paired visual and tactile data relating to cloth textures show that a good recognition performance of greater than 90% can be achieved by using the proposed DMCA framework. In addition, we find that the perception performance of either vision or tactile sensing can be improved by employing the shared representation space, compared to learning from unimodal data
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