79 research outputs found
Development of a Steering law experiment platform with haptic device Phantom Omni
Tatay De Pascual, A. (2010). Development of a Steering law experiment platform with haptic device Phantom Omni. http://hdl.handle.net/10251/8631.Archivo delegad
Generative replay underlies compositional inference in the hippocampal-prefrontal circuit
Human reasoning depends on reusing pieces of information by putting them together in new ways. However, very little is known about how compositional computation is implemented in the brain. Here, we ask participants to solve a series of problems that each require constructing a whole from a set of elements. With fMRI, we find that representations of novel constructed objects in the frontal cortex and hippocampus are relational and compositional. With MEG, we find that replay assembles elements into compounds, with each replay sequence constituting a hypothesis about a possible configuration of elements. The content of sequences evolves as participants solve each puzzle, progressing from predictable to uncertain elements and gradually converging on the correct configuration. Together, these results suggest a computational bridge between apparently distinct functions of hippocampal-prefrontal circuitry and a role for generative replay in compositional inference and hypothesis testing
FUN3D Manual: 13.3
This manual describes the installation and execution of FUN3D version 13.3, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status
NASA Tech Briefs, August 1994
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Neural replay in representation, learning and planning
Spontaneous neural activity is rarely the subject of investigation in cognitive neuroscience. This may be due to a dominant metaphor of cognition as the information processing unit, whereas internally generated thoughts are often considered as noise. Adopting a reinforcement learning (RL) framework, I consider cognition in terms of an agent trying to attain its internal goals. This framework motivated me to address in my thesis the role of spontaneous neural activity in human cognition. First, I developed a general method, called temporal delayed linear modelling (TDLM), to enable me to analyse this spontaneous activity. TDLM can be thought of as a domain general sequence detection method. It combines nonlinear classification and linear temporal modelling. This enables testing for statistical regularities in sequences of neural representations of a decoded state space. Although developed for use with human non- invasive neuroimaging data, the method can be extended to analyse rodent electrophysiological recordings. Next, I applied TDLM to study spontaneous neural activity during rest in humans. As in rodents, I found that spontaneously generated neural events tended to occur in structured sequences. These sequences are accelerated in time compared to those that related to actual experience (30 -50 ms state-to-state time lag). These sequences, termed replay, reverse their direction after reward receipt. Notably, this human replay is not a recapitulation of prior experience, but follows sequence implied by a learnt abstract structural knowledge, suggesting a factorized representation of structure and sensory information. Finally, I test the role of neural replay in model-based learning and planning in humans. Following reward receipt, I found significant backward replay of non-local experience with a 160 ms lag. This replay prioritises and facilitates the learning of action values. In a separate sequential planning task, I show these neural sequences go forward in direction, depicting the trajectory subjects about to take. The research presented in this thesis reveals a rich role of spontaneous neural activity in supporting internal computations that underpin planning and inference in human cognition
FUN3D Manual: 13.5
This manual describes the installation and execution of FUN3D (Fully-UNstructured three-dimensional CFD (Computational Fluid Dynamics) code) version 13.5, including optional dependent packages. FUN3D is a suite of computational fluid dynamics simulation and design tools that uses mixed-element unstructured grids in a large number of formats, including structured multiblock and overset grid systems. A discretely-exact adjoint solver enables efficient gradient-based design and grid adaptation to reduce estimated discretization error. FUN3D is available with and without a reacting, real-gas capability. This generic gas option is available only for those persons that qualify for its beta release status
Interfaces in crystalline materials
Interfaces such as grain boundaries in polycrystalline as well as
heterointerfaces in multiphase solids are ubiquitous in materials science and
engineering. Far from being featureless dividing surfaces between neighboring
crystals, elucidating features of solid-solid interfaces is challenging and
requires theoretical and numerical strategies to describe the physical and
mechanical characteristics of these internal interfaces. The first part of this
manuscript is concerned with interface-dominated microstructures emerging from
polymorphic structural (diffusionless) phase transformations. Under high
hydrostatic compression and shock-wave conditions, the pressure-driven phase
transitions and the formation of internal diffuse interfaces in iron are
captured by a thermodynamically consistent framework for combining nonlinear
elastoplasticity and multivariant phase-field approach at large strains. The
calculations investigate the crucial role played by the plastic deformation in
the morphological and microstructure evolution processes under high hydrostatic
compression and shock-wave conditions. The second section is intended to
describe such imperfect interfaces at a finer scale, for which the semicoherent
interfaces are described by misfit dislocation networks that produce a
lattice-invariant deformation which disrupts the uniformity of the lattice
correspondence across the interfaces and thereby reduces coherency. For the
past ten years, the constant effort has been devoted to combining the closely
related Frank-Bilby and O-lattice techniques with the Stroh sextic formalism
for the anisotropic elasticity theory of interfacial dislocation patterns. The
structures and energetics are quantified and used for rapid computational
design of interfaces with tailored misfit dislocation patterns, including the
interface sink strength for radiation-induced point defects and semicoherent
interfaces.Comment: 138 pages, 70 figure
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