1,720,987 research outputs found
Sensitivity Evaluation in Aerodynamic Optimal Design
Full text linkThe possibility to compute first- and second-derivatives of functionals subject to equality constraints given by state equations (and in particular non-linear systems of Partial Derivative Equations) allows us to use efficient techniques to solve several industrial-strength problems. Among possible applications that require knowledge of the derivatives, let us mention: aerodynamic shape optimization with gradient-based descent algorithms, propagation of uncertainties using perturbation techniques, robust optimization, and improvement of the accuracy of a functionnal using the adjoint state. In this work, we develop and analyze several strategies to evaluate the first- and second-derivatives of constrained functionals, using techniques based on Automatic Differentiation. Furthermore, we propose a descent algorithm for aerodynamic shape optimization, that is based on techniques of multi-level gradient, and which can be applied to different kinds of parameterization
Pupil dilation prediction of random events
No full textWe report the results of a conceptual replication of a study that reported that pupil dilation can predict potentially threatening random events above chance level. In this study, participants’ pupil dilation was used to predict the appearance of a threatening or a neutral stimulus, presented randomly in a double sequence of ten trials with replacement, i.e. replacing the chosen trial for the future extractions.
In the first experiment, with a sample of 100 participants, the average correct prediction was 55.9%, with a small difference between the two stimuli.
This effect was further tested in an exact pre-registered study where the average correct prediction was 58.7%. The reliability of these findings was checked utilizing both a frequentist and a Bayesian statistical parameters estimate approach.
These findings collectively support the hypothesis that pupil dilation can be used to anticipate random and therefore theoretically “unpredictable” events in an implicit unconscious way that is without a conscious awareness, and that this ability is another characteristic of the powerful anticipatory adaptive systems of our psychophysiological system
Does Psychophysiological Predictive Anticipatory Activity Predict Real or Future Probable Events?
No full textBackground: The possibility of predicting random future events before any sensory clues by using human physiology as a dependent variable has been supported by the meta- analysis of Mossbridge et al. (2012)1 and recent findings by Tressoldi et al. (2011 and 2013) and Mossbridge et al. (2014) defined this phenomenon predictive anticipatory activity (PAA).
Aim of the study: From a theoretical point of view, one interesting question is whether PAA is related to the effective, real future presentation of these stimuli or whether it is related only to the probability of their presentation.
Methods: This hypothesis was tested with four experiments, two using heart rate and two using pupil dilation as dependent variables.
Results: In all four experiments, both a neutral stimulus and a potentially threatening stimulus were predicted 7–10% above chance, independently from whether the predicted threatening stimulus was presented or not.
Conclusion: These findings are discussed with reference to the “grandfather paradox,” and some candidate explanations for this phenomena are presented
Saliency from orthogonal velocity component in texture segregation.
No full textWe found that a moving target line, more-vertical than 45 deg-oriented background lines, pops-out (d'=1.2) although it moves at the same speed of background elements and although it is invisible in static presentation (d'=.7). We suggest that the moving more-vertical target is more salient because the motion system responds to the orthogonal-velocity-component (V(perpendicular)=Delta d/Delta t sin theta) that is larger for the more-vertical target than for distracters. However, motion does not produce high d' when the target is more horizontal than background (d'=.6). This result is not expected if saliency resulted from the sum of saliency of orientation and motion independently coded but is instead predicted by visual search asymmetry. A line length effect on the moving target saliency also suggests that V(perpendicular) is extracted on the whole line and this operation is facilitated by line length in the same way for more-vertical and more-horizontal targets. Altogether, these results demonstrate that speed-based segmentation operating on V(perpendicular) not only affects speed and direction of motion discrimination, as previously demonstrated, but accounts for high saliency of image features that would otherwise prov
Effects of aging on interference control in selective attention and working memory
No full textWorking memory decay in advanced age has been attributed to a concurrent decrease in the ability to control interference. The present study contrasted a form of interference control in selective attention that acts upon the perception of external stimuli (access) with another form that operates on internal representations in working memory (deletion), in order to determine both of their effects on working memory efficiency in younger and older adults. Additionally, we compared memory performance under these access and deletion functions to performance in their respective control conditions. The results indicated that memory accuracy improved in both age groups from the access functions, but that only young adults benefited from the deletion functions. In addition, intrusion effects in the deletion condition were larger in older than in younger adults. The ability to control the irrelevant perception- and memory-elicited interference did not decline in general with advancing age; rather, the control mechanisms that operate on internal memory representations declined specifically
Exploring the suitability of Virtual Environments for safety training: Signals, Norms and Ambiguity in a Simulated Emergency Escape.
No full textThis study aims at exploring the suitability of virtual environments for safety training in large public spaces. A virtual library was constructed which simulated many of the physical and normative characteristics of the ‘real’ university library which was the target of the virtual safety training project. In the virtual library, two different types of signals (fixed red signs vs. moving green arrows) for guiding people to the emergency exits were presented, and their efficacy on escape times was tested in three different conditions, differing with respect to the distance of participants from the escape exits (measured according to the number of corners separating participants from direct visual discovery of the emergency exit). No significant differences between the different kinds of signals were found, whereas surprising discrepancies among the three conditions appeared. The differences in performance in the three conditions were contingent upon the presence in the virtual library of peculiar environmental features embodying social norms – like a red ribbon indicating no transit. Uncertainty about the sense of such normative features in the context of the simulated emergency made some participants prone to peculiar knowledge-based errors consisting of inadequate sense-making of the normative aspects of the ongoing situation. This kind of error shows that the simulation succeeded in capturing one of the crucial characteristics of ‘real’ social context: ambiguity, which mostly depends on the fact that the social norms structuring public spaces and defining their legitimate uses are often ill defined and context dependent. Every valid experience in safety training requires coping with ambiguity in situations
Igatools: An isogeometric analysis library
Full text linkWe present the design of an object oriented general purpose library for isogeometric analysis, where the mathematical concepts of the isogeometric method and their relationships are directly mapped into classes and their interactions. The encapsulation of mathematical concepts into interacting building blocks gives flexibility to use the library in a wide range of scientific areas and applications. We provide a precise framework for a lot of loose, available information regarding the implementation of the isogeometric method, and also discuss the similarities and differences between this and the finite element method. We also describe how to implement this proposed design in a C++11 open source library, \textttigatools (http://www.igatools.org). The library uses advanced object oriented and generic programming techniques to ensure reusability, reliability, and maintainability of the source code. It includes isogeometric elements of the h-div and h-curl type, and supports the development of dimension independent code (including manifolds and tensor-valued spaces). We finally present a number of code examples to illustrate the flexibility and power of the library, including surface domains, nonlinear elasticity, and Navier--Stokes computations on nontrivial geometries.Fil: Pauletti, Miguel Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Instituto de Matemática Aplicada del Litoral. Universidad Nacional del Litoral. Instituto de Matemática Aplicada del Litoral; ArgentinaFil: Martinelli, Massimiliano. Consiglio Nazionale delle Ricerche. Istituto di Matematica Applicata e Tecnologie Informatiche; ItaliaFil: Cavallini, Nicola. Scuola Internazionale Superiore di Studi Avanzati; ItaliaFil: Antolin, Pablo. Università degli Studi di Pavia. Dipartimento di Ingegneria Civile ed Architettura; Itali
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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