24,732 research outputs found

    Norwegian Aerospace Activities: an Overview

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    Excerpts from a Governmental Investigation concerning Norwegian participation in the European Space Organization (ESA) is presented. The implications and advantages of such a move and a suggestion for the reorganization of Norwegian Aerospace activity is given

    Polar communications: Status and recommendations. Report of the Science Working Group

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    The capabilities of the existing communication links within the polar regions, as well as between the polar regions and the continental United States, are summarized. These capabilities are placed in the context of the principal scientific disciplines that are active in polar research, and in the context of how scientists both utilize and are limited by present technologies. Based on an assessment of the scientific objectives potentially achievable with improved communication capabilities, a list of requirements on and recommendations for communication capabilities necessary to support polar science over the next ten years is given

    Clear air turbulence

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    Research on forecasting, detection, and incidents of clear air turbulenc

    On non-normality and classification of amplification mechanisms in stability and resolvent analysis

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    We seek to quantify non-normality of the most amplified resolvent modes and predict their features based on the characteristics of the base or mean velocity profile. A 2-by-2 model linear Navier-Stokes (LNS) operator illustrates how non-normality from mean shear distributes perturbation energy in different velocity components of the forcing and response modes. The inverse of their inner product, which is unity for a purely normal mechanism, is proposed as a measure to quantify non-normality. In flows where there is downstream spatial dependence of the base/mean, mean flow advection separates the spatial support of forcing and response modes which impacts the inner product. Success of mean stability analysis depends on the normality of amplification. If the amplification is normal, the resolvent operator written in its dyadic representation reveals that the adjoint and forward stability modes are proportional to the forcing and response resolvent modes. If the amplification is non-normal, then resolvent analysis is required to understand the origin of observed flow structures. Eigenspectra and pseudospectra are used to characterize these phenomena. Two test cases are studied: low Reynolds number cylinder flow and turbulent channel flow. The first deals mainly with normal mechanisms and quantification of non-normality using the inverse inner product of the leading forcing and response modes agrees well with the product of the resolvent norm and distance between the imaginary axis and least stable eigenvalue. In turbulent channel flow, structures result from both normal and non-normal mechanisms. Mean shear is exploited most efficiently by stationary disturbances while bounds on the pseudospectra illustrate how non-normality is responsible for the most amplified disturbances at spatial wavenumbers and temporal frequencies corresponding to well-known turbulent structures

    The Continued Relevance of the Irrelevance-of-Motive Maxim

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    The irrelevance-of-motive maxim-the longstanding principle that a defendant\u27s motives are irrelevant to criminal liability-has come under attack. Critics of this maxim claim that motives, under any plausible conception of the term, are in fact relevant in the criminal law. According to these critics, the only way to defend the truth of the irrelevance-of-motive maxim is to render it true by definition, by defining motive as the subcategory of intentions that are irrelevant to criminal liability. This Note defends the irrelevance-of-motive maxim by applying a plausible conception of motive that conforms to the historical meaning of the term. With the proper definition in place, the irrelevance-of-motive maxim can be understood as stating a valid principle of criminal law, defied only by the advent of a certain kind of bias crime legislation

    Smart helmet: wearable multichannel ECG & EEG

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    Modern wearable technologies have enabled continuous recording of vital signs, however, for activities such as cycling, motor-racing, or military engagement, a helmet with embedded sensors would provide maximum convenience and the opportunity to monitor simultaneously both the vital signs and the electroencephalogram (EEG). To this end, we investigate the feasibility of recording the electrocardiogram (ECG), respiration, and EEG from face-lead locations, by embedding multiple electrodes within a standard helmet. The electrode positions are at the lower jaw, mastoids, and forehead, while for validation purposes a respiration belt around the thorax and a reference ECG from the chest serve as ground truth to assess the performance. The within-helmet EEG is verified by exposing the subjects to periodic visual and auditory stimuli and screening the recordings for the steady-state evoked potentials in response to these stimuli. Cycling and walking are chosen as real-world activities to illustrate how to deal with the so-induced irregular motion artifacts, which contaminate the recordings. We also propose a multivariate R-peak detection algorithm suitable for such noisy environments. Recordings in real-world scenarios support a proof of concept of the feasibility of recording vital signs and EEG from the proposed smart helmet

    Surgery and the Spectrum of the Dirac Operator

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    We show that for generic Riemannian metrics on a simply-connected closed spin manifold of dimension at least 5 the dimension of the space of harmonic spinors is no larger than it must be by the index theorem. The same result holds for periodic fundamental groups of odd order. The proof is based on a surgery theorem for the Dirac spectrum which says that if one performs surgery of codimension at least 3 on a closed Riemannian spin manifold, then the Dirac spectrum changes arbitrarily little provided the metric on the manifold after surgery is chosen properly.Comment: 23 pages, 4 figures, to appear in J. Reine Angew. Mat
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