1,856,050 research outputs found
A Priori Bootstrapping
No full textA sceptical scenario is a situation in which your experiences are in some undetectable way unreliable guides to the truth - say, because you are being deceived by a demon (or the like). According to a certain sceptical argument, you cannot have any justification for believing the proposition that you are not in a sceptical scenario, since such justification would have to be either a priori or empirical, but neither a priori nor empirical justification for this proposition is available. In fact, however, if you are justified in believing ordinary propositions about the external world on the basis of your experiences, it follows that you also have a priori justification for believing that you are not in a sceptical scenario. If experiences justify ordinary beliefs in this way, then there is at least one possible process of non-empirical reasoning - the "a priori bootstrapping reasoning" - that can lead you to a justified belief in the proposition that you are not in a sceptical scenario. This point leaves open the question of why experiences justify ordinary beliefs; but it seems to provide an answer to the sceptical argument, and it helps to illuminate the nature of a priori justification
Fast GMTI Algorithm For Traffic Monitoring Based On A Priori Knowledge
No full textIn this paper a fast a priori knowledge-based ground moving target indication and parameter estimation algorithm applicable to single- as well as to multi-channel synthetic aperture airborne radar data is presented. The algorithm operates directly on range-compressed data. Only the intersection points of the moving vehicle signals with the a priori known road axes, which are mapped into the range-compressed data array, are evaluated. For moving vehicle detection and parameter estimation for each considered road point basically only one single FFT has to be performed. Hence, the required computational power is low and the algorithm is well suited for real-time traffic monitoring applications. The proposed algorithm enables the estimation of the whole position and velocity vectors of the detected moving vehicles, even if only a single-channel synthetic aperture radar system is used
On adaptive sliding mode control without a priori bounded uncertainty
No full textAdaptive Sliding Mode Control (ASMC) aims to adapt the switching gain in such a way to cope with possibly unknown uncertainty. In state-of-the-art ASMC methods, a priori boundedness of the uncertainty is crucial to ensure boundedness for the switching gain and uniformly ultimately boundedness. A priori bounded uncertainty might impose a priori bounds on the system state before obtaining closed-loop stability. A design removing this assumption is still missing in literature. A positive answer to this quest is given by this note where a novel ASMC methodology is proposed which does not require a priori bounded uncertainty. An illustrative example is presented to highlight the main features of the approach, after which a general class of Euler–Lagrange systems is taken as a case study to show the applicability of the proposed design.Accepted Author ManuscriptShip Design, Production and OperationsTeam Bart De Schutte
Brain polarization in humans: a reappraisal of an old tool for prolonged non-invasive modulation of brain excitability
No full textDirect current (DC) is very effective in modulating spontaneous neuronal firing. The history of electrophysiology starts with the discovery of the biological effects of DC and as early as two centuries ago scalp DC was used to treat mental disorder. Psychophysiological investigations suggested a possible effect of scalp DC in humans. More recently several studies assessed, with motor potentials evoked by transcranial brain stimulation, the motor-cortical excitability changes induced by scalp DC. Even weak DCs pass through the scalp and influence human brain activity. DCs delivered at relatively strong intensities (1 mA) and for long periods (10 min or so), not only influence (either increase or decrease) brain excitability during their application in normal subjects, but induce persistent changes in excitability after their offset that, at least in the motor cortex, can last for almost I h. Scalp DC might represent a non-invasive simple and valuable potential treatment for psychiatric and neurologic diseases with changes in brain excitability or focally abnormal (increased or decreased) function. (C) 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Science Ireland Ltd. All rights reserved
A priori error analysis of two force-based atomistic/continuum models of a periodic chain
Full text linkThe force-based quasicontinuum (QCF) approximation is a non-conservative atomistic/continuum hybrid model for the simulation of defects in crystals. We present an a priori error analysis of the QCF method, applied to a one-dimensional periodic chain, that is valid for an arbitrary interaction range, large deformations, and takes coarse-graining into account. Our main tool in this analysis is a new concept of atomistic stress. Moreover, we formulate a new atomistic/continuum coupling mechanism based on coupling stresses instead of forces and extend the a priori analysis to this new method. We show that the new method has several theoretical advantages over the original QCF method
Safety criteria for transcranial direct current stimulation (tDCS) in humans - Reply to Dr. Paulus
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