1,056 research outputs found
Several approaches for optical data storage in thin organic films
Date du colloque : 12/2012International audienc
Reversible recording medium based on optical storage of information, method of reversible recording on such a medium.
A reversible recording medium based on optical storage of at least one item ofinformation within a support material, includes at least one layer of support material having: base molecules able to take, in a local zone, a first collective state of molecules able to generate a first signal of second harmonic characteristic of this first collective state of molecules when excited by electromagnetic reading radiation; the base molecules having the first collective state of molecules able to transform, at least in part, into transformed molecules so as to pass to a second collective state of molecules when excited by electromagnetic writing radiation, the molecules having the second collective state of molecules able to generate a second signal of second harmonic characteristic of this second collective state of molecules when excited by the electromagnetic reading radiation. The molecules exhibit a molecular structure based on a coumarin skeleton of Formula (I)
Reversible Two-Photon Optical Data Storage in Coumarin-Based Copolymers
A functionalized polymer film allowing for a complete and straightforward second-harmonic generation (SHG)-assisted high-contrast writing?reading?erasing?writing sequence is proposed. The whole process is supported by the reversible photoinduced dimerization of a coumarin chromophore and enables efficient optical data storage that can be detected only by SHG imaging
Average-Case Optimal Approximate Circular String Matching
Approximate string matching is the problem of finding all factors of a text t
of length n that are at a distance at most k from a pattern x of length m.
Approximate circular string matching is the problem of finding all factors of t
that are at a distance at most k from x or from any of its rotations. In this
article, we present a new algorithm for approximate circular string matching
under the edit distance model with optimal average-case search time O(n(k + log
m)/m). Optimal average-case search time can also be achieved by the algorithms
for multiple approximate string matching (Fredriksson and Navarro, 2004) using
x and its rotations as the set of multiple patterns. Here we reduce the
preprocessing time and space requirements compared to that approach
Non-linear optical and electrical properties of ZnO doped Ni Thin Films obtained using spray ultrasonic technique
In the present study zinc oxide doped Nickel thin films (ZnO:Ni) were deposited on glass substrates using a chemical spray ultrasonic technique. The effect of Ni concentration on the structural, electrical, optical, and non-linear optical (NLO) properties of the ZnO:Ni thin films was investigated. The films were analyzed using X-ray diffraction (XRD), profilometry and optical transmittance. A polycrystalline structure with a preferential growth along the ZnO (002) plane was found, the optical transmittance was found to be higher than 80% and the band gap (E(g)) varied from 3.19 to 3.27 eV. The value of the electrical conductivity was found. Moreover, the effective non-linear quadratic and cubic electronic susceptibilities of thin film samples were determined by the SHG and THG techniques, working at 1064 nm. (C) 2011 Elsevier B.V. All rights reserved
Enhanced ULF radiation observed by DEMETER two months around the strong 2010 Haiti earthquake
In this paper we study the energy of ULF electromagnetic waves that have been
recorded by the satellite DEMETER, during its passing over Haiti before and
after a destructive earthquake. This earthquake occurred on 12/1/2010, at
geographic Latitude 18.46o and Longitude 287.47o, with Magnitude 7.0 R.
Specifically, we are focusing on the variations of energy of Ez-electric field
component concerning a time period of 100 days before and 50 days after the
strong earthquake. In order to study these variations, we developed a novel
method that can be divided in two stages: first we filter the signal keeping
only the very low frequencies and afterwards we eliminate its trend using
techniques of Singular Spectrum Analysis, combined with a third-degree
polynomial filter. As it is shown, a significant increase in energy is observed
for the time interval of 30 days before the strong earthquake. This result
clearly indicates that the change in the energy of ULF electromagnetic waves
could be related to strong precursory earthquake phenomena. Moreover, changes
in energy were also observed 25 days after the strong earthquake associated
with strong aftershock activity. Finally, we present results concerning the
comparison in changes in Energy during night and day passes of the satellite
over Haiti, which showed differences in the mean energy values, but similar
results as far as the rate of energy change is concerned.Comment: 16 pages, 7 figures, submitted to NHES
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