2,518 research outputs found
ROSE: a Package for Binary Imbalanced Learning
The ROSE package provides functions to deal with binary classification problems in the presence of imbalanced classes. Artificial balanced samples are generated according to a smoothed
bootstrap approach and allow for aiding both the phases of estimation and accuracy evaluation of a binary classifier in the presence of a rare class. Functions that implement more traditional remedies for
the class imbalance and different metrics to evaluate accuracy are also provided. These are estimated by holdout, bootstrap or cross-validation methods
Automorphism groups and new constructions of maximum additive rank metric codes with restrictions
Let such that . A -code
is a subset of order square
matrices with the property that for all pairs of distinct elements in
, the rank of their difference is greater than or equal to . A
-code with as many as possible elements is called a maximum -code. The
integer is also called the minimum distance of the code. When , a
classical example of such an object is the so-called generalized Gabidulin
code. There exist several classes of maximum -codes made up respectively of
symmetric, alternating and hermitian matrices. In this article we focus on such
examples. Precisely, we determine their automorphism groups and solve the
equivalence issue for them. Finally, we exhibit a maximum symmetric -code
which is not equivalent to the one with same parameters known so far
Preface
This is the preface of the special volume of Discrete Mathematics dedicated to Combinatorics 2008 we curated as guest editors
Laboratory Tests of Low Density Astrophysical Equations of State
Clustering in low density nuclear matter has been investigated using the
NIMROD multi-detector at Texas A&M University. Thermal coalescence modes were
employed to extract densities, , and temperatures, , for evolving
systems formed in collisions of 47 MeV Ar + Sn,Sn
and Zn + Sn, Sn. The yields of , , He, and
He have been determined at = 0.002 to 0.032 nucleons/fm and
= 5 to 10 MeV. The experimentally derived equilibrium constants for
particle production are compared with those predicted by a number of
astrophysical equations of state. The data provide important new constraints on
the model calculations.Comment: 5 pages, 3 figure
Experimental Determination of In-Medium Cluster Binding Energies and Mott Points in Nuclear Matter
In medium binding energies and Mott points for , , He and
clusters in low density nuclear matter have been determined at specific
combinations of temperature and density in low density nuclear matter produced
in collisions of 47 MeV Ar and Zn projectiles with Sn
and Sn target nuclei. The experimentally derived values of the in
medium modified binding energies are in good agreement with recent theoretical
predictions based upon the implementation of Pauli blocking effects in a
quantum statistical approach.Comment: 5 pages, 3 figure
Families of twisted tensor product codes
Using geometric properties of the variety \cV_{r,t}, the image under the
Grassmannian map of a Desarguesian -spread of \PG(rt-1,q), we
introduce error correcting codes related to the twisted tensor product
construction, producing several families of constacyclic codes. We exactly
determine the parameters of these codes and characterise the words of minimum
weight.Comment: Keywords: Segre Product, Veronesean, Grassmannian, Desarguesian
spread, Subgeometry, Twisted Product, Constacyclic error correcting code,
Minimum weigh
Critical Behavior in Light Nuclear Systems: Experimental Aspects
An extensive experimental survey of the features of the disassembly of a
small quasi-projectile system with 36, produced in the reactions of 47
MeV/nucleon Ar + Al, Ti and Ni, has been carried
out. Nuclei in the excitation energy range of 1-9 MeV/u have been investigated
employing a new method to reconstruct the quasi-projectile source. At an
excitation energy 5.6 MeV/nucleon many observables indicate the presence
of maximal fluctuations in the de-excitation processes. The fragment
topological structure shows that the rank sorted fragments obey Zipf's law at
the point of largest fluctuations providing another indication of a liquid gas
phase transition. The caloric curve for this system shows a monotonic increase
of temperature with excitation energy and no apparent plateau. The temperature
at the point of maximal fluctuations is MeV. Taking this
temperature as the critical temperature and employing the caloric curve
information we have extracted the critical exponents , and
from the data. Their values are also consistent with the values of the
universality class of the liquid gas phase transition. Taken together, this
body of evidence strongly suggests a phase change in an equilibrated mesoscopic
system at, or extremely close to, the critical point.Comment: Physical Review C, in press; some discussions about the validity of
excitation energy in peripheral collisions have been added; 24 pages and 32
figures; longer abstract in the preprin
Evidence of Critical Behavior in the Disassembly of Nuclei with A ~ 36
A wide variety of observables indicate that maximal fluctuations in the
disassembly of hot nuclei with A ~ 36 occur at an excitation energy of 5.6 +-
0.5 MeV/u and temperature of 8.3 +- 0.5 MeV. Associated with this point of
maximal fluctuations are a number of quantitative indicators of apparent
critical behavior. The associated caloric curve does not appear to show a
flattening such as that seen for heavier systems. This suggests that, in
contrast to similar signals seen for liquid-gas transitions in heavier nuclei,
the observed behavior in these very light nuclei is associated with a
transition much closer to the critical point.Comment: v2: Major changes, new model calculations, new figure
Towards the critical behavior for the light nuclei by NIMROD detector
The critical behavior for the light nuclei with A has been
investigated experimentally by the NIMROD multi-detectors. The wide variety of
observables indicate the critical point has been reached in the disassembly of
hot nuclei at an excitation energy of 5.60.5 MeV/u.Comment: 4 pages, 2 figures; Proceeding of 18th Nuclear Physics Division
Conference of the Euro. Phys. Society (NPDC18) "Phase transitions in strongly
interacting matter", Prague, 23.8.-29.8. 2004. To be published in Nuclear
Physics
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