191 research outputs found
OMP-type Algorithm with Structured Sparsity Patterns for Multipath Radar Signals
A transmitted, unknown radar signal is observed at the receiver through more
than one path in additive noise. The aim is to recover the waveform of the
intercepted signal and to simultaneously estimate the direction of arrival
(DOA). We propose an approach exploiting the parsimonious time-frequency
representation of the signal by applying a new OMP-type algorithm for
structured sparsity patterns. An important issue is the scalability of the
proposed algorithm since high-dimensional models shall be used for radar
signals. Monte-Carlo simulations for modulated signals illustrate the good
performance of the method even for low signal-to-noise ratios and a gain of 20
dB for the DOA estimation compared to some elementary method
New Renaissance (The)
Les sages de ce comité ont procédé à l\u27étude du projet de numérisation de l\u27ensemble du patrimoine culturel européen et proposent dans ce rapport une série de recommandations visant à encadrer cet ambitieux programme afin de :
-partager notre patrimoine commun, dans toute sa richesse et sa diversité ;
- relier notre passé à notre présent ;
- préserver cet héritage pour les générations futures ;
- protĂ©ger les intĂ©rĂȘts des crĂ©ateurs europĂ©ens ;
- favoriser la créativité, celles des professionnels comme celles des amateur
Variations on a theme of Heisenberg, Pauli and Weyl
The parentage between Weyl pairs, generalized Pauli group and unitary group
is investigated in detail. We start from an abstract definition of the
Heisenberg-Weyl group on the field R and then switch to the discrete
Heisenberg-Weyl group or generalized Pauli group on a finite ring Z_d. The main
characteristics of the latter group, an abstract group of order d**3 noted P_d,
are given (conjugacy classes and irreducible representation classes or
equivalently Lie algebra of dimension d**3 associated with P_d). Leaving the
abstract sector, a set of Weyl pairs in dimension d is derived from a polar
decomposition of SU(2) closely connected to angular momentum theory. Then, a
realization of the generalized Pauli group P_d and the construction of
generalized Pauli matrices in dimension d are revisited in terms of Weyl pairs.
Finally, the Lie algebra of the unitary group U(d) is obtained as a subalgebra
of the Lie algebra associated with P_d. This leads to a development of the Lie
algebra of U(d) in a basis consisting of d**2 generalized Pauli matrices. In
the case where d is a power of a prime integer, the Lie algebra of SU(d) can be
decomposed into d-1 Cartan subalgebras.Comment: Dedicated to the memory of Mosh\'e Flato on the occasion of the tenth
anniversary of his deat
Open Data for Global Science
The global science system stands at a critical juncture. On the one hand, it is overwhelmed by a hidden avalanche of ephemeral bits that are central components of modern research and of the emerging âcyberinfrastructureâ4 for e-Science.5 The rational management and exploitation of this cascade of digital assets offers boundless opportunities for research and applications. On the other hand, the ability to access and use this rising flood of data seems to lag behind, despite the rapidly growing capabilities of information and communication technologies (ICTs) to make much more effective use of those data. As long as the attention for data policies and data management by researchers, their organisations and their funders does not catch up with the rapidly changing research environment, the research policy and funding entities in many cases will perpetuate the systemic inefficiencies, and the resulting loss or underutilisation of valuable data resources derived from public investments. There is thus an urgent need for rationalised national strategies and more coherent international arrangements for sustainable access to public research data, both to data produced directly by government entities and to data generated in academic and not-for-profit institutions with public funding. In this chapter, we examine some of the implications of the âdata drivenâ research and possible ways to overcome existing barriers to accessibility of public research data. Our perspective is framed in the context of the predominantly publicly funded global science system. We begin by reviewing the growing role of digital data in research and outlining the roles of stakeholders in the research community in developing data access regimes. We then discuss the hidden costs of closed data systems, the benefits and limitations of openness as the default principle for data access, and the emerging open access models that are beginning to form digitally networked commons. We conclude by examining the rationale and requirements for developing overarching international principles from the top down, as well as flexible, common-use contractual templates from the bottom up, to establish data access regimes founded on a presumption of openness, with the goal of better capturing the benefits from the existing and future scientific data assets. The âPrinciples and Guidelines for Access to Research Data from Public Fundingâ from the Organisation for Economic Cooperation and Development (OECD), reported on in another article by Pilat and Fukasaku,6 are the most important recent example of the high-level (inter)governmental approach. The common-use licenses promoted by the Science Commons are a leading example of flexible arrangements originating within the community. Finally, we should emphasise that we focus almost exclusively on the policyâthe institutional, socioeconomic, and legal aspects of data accessârather than on the technical and management practicalities that are also important, but beyond the scope of this article
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