131,104 research outputs found
Semi-relativistic description of quasielastic neutrino reactions and superscaling in a continuum shell model
The so-called semi-relativistic expansion of the weak charged current in
powers of the initial nucleon momentum is performed to describe
charge-changing, quasielastic neutrino reactions at
intermediate energies. The quality of the expansion is tested by comparing with
the relativistic Fermi gas model using several choices of kinematics of
interest for ongoing neutrino oscillation experiments. The new current is then
implemented in a continuum shell model together with relativistic kinematics to
investigate the scaling properties of and cross
sections.Comment: 33 pages, 10 figures, to appear in PR
Neutrino Interactions Importance for Nuclear Physics
We review the general interplay between Nuclear Physics and neutrino-nucleus
cross sections at intermediate and high energies. The effects of different
reaction mechanisms over the neutrino observables are illustrated with examples
in calculations using several nuclear models and ingredients.Comment: To appear in the proceedings of 6th International Workshop on
Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt09), Sitges, Spain,
18 - 22 May 200
Lower and upper estimates on the excitation threshold for breathers in DNLS lattices
We propose analytical lower and upper estimates on the excitation threshold
for breathers (in the form of spatially localized and time periodic solutions)
in DNLS lattices with power nonlinearity. The estimation depending explicitly
on the lattice parameters, is derived by a combination of a comparison argument
on appropriate lower bounds depending on the frequency of each solution with a
simple and justified heuristic argument. The numerical studies verify that the
analytical estimates can be of particular usefulness, as a simple analytical
detection of the activation energy for breathers in DNLS lattices.Comment: 10 pages, 3 figure
Ultrasonic, molecular and mechanical testing diagnostics in natural fibre reinforced, polymer-stabilised earth blocks
The aim of this research study was to evaluate the influence of utilising natural polymers as a form of soil stabilization, in order to assess their potential for use in building applications. Mixtures were stabilized with a natural polymer (alginate) and reinforced with wool fibres in order to improve the overall compressive and flexural strength of a series of composite materials. Ultrasonic pulse velocity (UPV) and mechanical strength testing techniques were then used to measure the porous properties of the manufactured natural polymer-soil composites, which were formed into earth blocks. Mechanical tests were carried out for three different clays which showed that the polymer increased the mechanical resistance of the samples to varying degrees, depending on the plasticity index of each soil. Variation in soil grain size distributions and Atterberg limits were assessed and chemical compositions were studied and compared. X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), and energy dispersive X-ray fluorescence (EDXRF) techniques were all used in conjunction with qualitative identification of the aggregates. Ultrasonic wave propagation was found to be a useful technique for assisting in the determination of soil shrinkage characteristics and fibre-soil adherence capacity and UPV results correlated well with the measured mechanical properties
Distributed boundary tracking using alpha and Delaunay-Cech shapes
For a given point set in a plane, we develop a distributed algorithm to
compute the shape of . shapes are well known geometric
objects which generalize the idea of a convex hull, and provide a good
definition for the shape of . We assume that the distances between pairs of
points which are closer than a certain distance are provided, and we show
constructively that this information is sufficient to compute the alpha shapes
for a range of parameters, where the range depends on .
Such distributed algorithms are very useful in domains such as sensor
networks, where each point represents a sensing node, the location of which is
not necessarily known.
We also introduce a new geometric object called the Delaunay-\v{C}ech shape,
which is geometrically more appropriate than an shape for some cases,
and show that it is topologically equivalent to shapes
Equations, inequations and inequalities characterizing the configurations of two real projective conics
Couples of proper, non-empty real projective conics can be classified modulo
rigid isotopy and ambient isotopy.
We characterize the classes by equations, inequations and inequalities in the
coefficients of the quadratic forms defining the conics.
The results are well--adapted to the study of the relative position of two
conics defined by equations depending on parameters.Comment: 31 pages. See also
http://emmanuel.jean.briand.free.fr/publications/twoconics/ Added references
to important prior work on the subject. The title changed accordingly. Some
typos and imprecisions corrected. To be published in Applicable Algebra in
Engineering, Communication and Computin
Stabilization of the Peregrine soliton and Kuznetsov-Ma breathers by means of nonlinearity and dispersion management
We demonstrate a possibility to make rogue waves (RWs) in the form of the
Peregrine soliton (PS) and Kuznetsov-Ma breathers (KMBs) effectively stable
objects, with the help of properly defined dispersion or nonlinearity
management applied to the continuous-wave (CW) background supporting the RWs.
In particular, it is found that either management scheme, if applied along the
longitudinal coordinate, making the underlying nonlinear Schr\"odinger equation
(NLSE) selfdefocusing in the course of disappearance of the PS, indeed
stabilizes the global solution with respect to the modulational instability of
the background. In the process, additional excitations are generated, namely,
dispersive shock waves and, in some cases, also a pair of slowly separating
dark solitons. Further, the nonlinearity-management format, which makes the
NLSE defocusing outside of a finite domain in the transverse direction, enables
the stabilization of the KMBs, in the form of confined oscillating states. On
the other hand, a nonlinearity-management format applied periodically along the
propagation direction, creates expanding patterns featuring multiplication of
KMBs through their cascading fission.Comment: Physics Letters A, on pres
A Seidel-Walsh theorem with linear differential operators
Assume that {Sn}∞1 is a sequence of automorphisms of the open unit disk D and that {Tn}∞1 is a sequence of linear differential operators with constant coefficients, both of them satisfying suitable conditions. We prove that for certain spaces X of holomorphic
functions in the open unit disk, the set of functions f ∈ X such that {(Tnf) ◦ Sn : n ∈ N} is dense in H(D) is residual in X. This extends
the Seidel-Walsh theorem together with some subsequent results.Dirección General de Enseñanza Superior (DGES). EspañaJunta de Andalucí
Feed-forward Space Vector Modulation for Single-Phase Multilevel Cascade Converters with any DC voltage ratio
Modulation techniques for multilevel converters
can create distorted output voltages and currents if the DC link
voltages are unbalanced. This situation can be avoided if the
instantaneous DC voltage error is not taken into account in the
modulation process. This paper proposes a feed-forward space
vector modulation method for a single-phase multilevel cascade
converter. Using this modulation technique, the modulated output
voltage of the power converter always generates the reference
determined by the controller even in worst case voltage unbalance
conditions. In addition the possibility of optimizing the DC
voltage ratio between the H-bridges of the power converter is
introduced. Experimental results from a 5kVA prototype are
presented in order to validate the proposed modulation technique
LVDS Serial AER Link performance
Address-Event-Representation (AER) is a
communication protocol for transferring asynchronous events
between VLSI chips, originally developed for bio-inspired
processing systems (for example, image processing). Such
systems may consist of a complicated hierarchical structure
with many chips that transmit data among them in real time,
while performing some processing (for example, convolutions).
The event information is transferred using a high speed digital
parallel bus (typically 16 bits and 20ns-40ns per event). This
paper presents a testing platform for AER systems that allows
analysing a LVDS Serial AER link produced by a Spartan 3
FPGA, or by a commercial LVDS transceiver. The interface
allows up to 0.728 Gbps (~40Mev/s, 16 bits/ev). The eye
diagram ensures that the platform could support 1.2 Gbps.Commission of the European Communities IST-2001-34124 (CAVIAR)Comisión Interministerial de Ciencia y Tecnología TIC-2003-08164-C03-0
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