8,786 research outputs found
Weil's converse theorem with poles
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Information reuse in dynamic spectrum access
Dynamic spectrum access (DSA), where the permission to use slices of radio spectrum is dynamically shifted (in time an in different geographical areas) across various communications services and applications, has been an area of interest from technical and public policy perspectives over the last decade. The underlying belief is that this will increase spectrum utilization, especially since many spectrum bands are relatively unused, ultimately leading to the creation of new and innovative services that exploit the increase in spectrum availability. Determining whether a slice of spectrum, allocated or licensed to a primary user, is available for use by a secondary user at a certain time and in a certain geographic area is a challenging task. This requires 'context information' which is critical to the operation of DSA. Such context information can be obtained in several ways, with different costs, and different quality/usefulness of the information. In this paper, we describe the challenges in obtaining this context information, the potential for the integration of various sources of context information, and the potential for reuse of such information for related and unrelated purposes such as localization and enforcement of spectrum sharing. Since some of the infrastructure for obtaining finegrained context information is likely to be expensive, the reuse of this infrastructure/information and integration of information from less expensive sources are likely to be essential for the economical and technological viability of DSA. © 2013 IEEE
Strong light fields coax intramolecular reactions on femtosecond time scales
Energetic H ions are formed as a result of intra-molecular
rearrangement during fragmentation of linear alcohols (methanol, ethanol,
propanol, hexanol, and dodecanol) induced by intense optical fields produced by
100 fs long, infrared, laser pulses of peak intensity 8 W
cm. Polarization dependent measurements show, counterintuitively, that
rearrangement is induced by the strong optical field within a single laser
pulse, and that it occurs before Coulomb explosion of the field-ionized
multiply charged alcohols
Test vectors for Rankin-Selberg -functions
We study the local zeta integrals attached to a pair of generic
representations of , , over a -adic
field. Through a process of unipotent averaging we produce a pair of
corresponding Whittaker functions whose zeta integral is non-zero, and we
express this integral in terms of the Langlands parameters of and .
In many cases, these Whittaker functions also serve as a test vector for the
associated Rankin-Selberg (local) -function.Comment: arXiv admin note: text overlap with arXiv:1804.0772
When is electromagnetic spectrum fungible?
Fungibility is a common assumption for market-based spectrum management. In this paper, we explore the dimensions of practical fungibility of frequency bands from the point of view of the spectrum buyer who intends to use it. The exploration shows that fungibility is a complex, multidimensional concept that cannot casually be assumed. We develop two ideas for quantifying fungibility-(i) of a fungibility space in which the 'distance' between two slices of spectrum provides score of fungibility and (ii) a probabilistic score of fungibility. © 2012 IEEE
Online Public Access Catalog Through Libsys : An Experience
With the advent of Online Public Access Catalogs, librarians and their
staff have been freed from the labor-intensive processes involved in the creation
and maintenance of card catalogue. At the Indian statistical Institute library, this
new system has been devoted to enhancing access to the library collections.
Libsys, a commercially available integrated house keeping software, is being
used at ISI BC library. The experience of author in using modules of Libsys is
discussed
Auralization of Amplitude Modulated Helicopter Flyover Noise
Rotorcraft noise is an active field of study as the sound produced by these vehicles is often found to be annoying. A means to auralize rotorcraft flyover noise is sought to help understand the factors leading to annoyance. Previous work by the authors auralized a complete flyover event in which the source noise synthesis traversed a range of emission angles. The source noise definition process for the synthesis used helicopter flyover recordings. Although this process yielded both periodic and aperiodic (modulation) components at a set of discrete emission angles, only the periodic components were used in the previous work to synthesize the sound of the flyover event. In the current work, aperiodic amplitude modulation is incorporated into the source noise synthesis to improve its fidelity toward assessing rotorcraft noise annoyance. The method is demonstrated using ground recordings from a flight test of the AS350 helicopter for the source noise definition
Internal avalanches in models of granular media
We study the phenomenon of internal avalanching within the context of
recently introduced lattice models of granular media. The avalanche is produced
by pulling out a grain at the base of the packing and studying how many grains
have to rearrange before the packing is once more stable. We find that the
avalanches are long-ranged, decaying as a power-law. We study the distriution
of avalanches as a function of the density of the packing and find that the
avalanche distribution is a very sensitive structural probe of the system.Comment: 12 pages including 9 eps figures, LaTeX. To appear in Fractal
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