5,261 research outputs found
Data and performance of an active-set truncated Newton method with non-monotone line search for bound-constrained optimization
In this data article, we report data and experiments related to the research article entitled âA Two-Stage Active-Set Algorithm for Bound-Constrained Optimizationâ, by Cristofari et al. (2017). The method proposed in Cristofari et al. (2017), tackles optimization problems with bound constraints by properly combining an active-set estimate with a truncated Newton strategy. Here, we report the detailed numerical experience performed over a commonly used test set, namely CUTEst (Gould et al., 2015). First, the algorithm ASA-BCP proposed in Cristofari et al. (2017) is compared with the related method NMBC (De Santis et al., 2012). Then, a comparison with the renowned methods ALGENCAN (Birgin and MartĂnez et al., 2002) and LANCELOT B (Gould et al., 2003) is reported
Coordination defects in a-Si and a-Si:H : a characterization from first principles calculations
We study by means of first-principles pseudopotential method the coordination
defects in a-Si and a-Si:H, also in their formation and their evolution upon
hydrogen interaction. An accurate analysis of the valence charge distribution
and of the ``electron localization function'' (ELF) allows to resolve possible
ambiguities in the bonding configuration, and in particular to identify clearly
three-fold (T_3) and five-fold (T_5) coordinated defects. We found that
electronic states in the gap can be associated to both kind of defects, and
that in both cases the interaction with hydrogen can reduce the density of
states in the gap.Comment: To appear in Philos. Ma
A nonmonotone GRASP
A greedy randomized adaptive search procedure (GRASP) is an itera-
tive multistart metaheuristic for difficult combinatorial optimization problems. Each
GRASP iteration consists of two phases: a construction phase, in which a feasible
solution is produced, and a local search phase, in which a local optimum in the
neighborhood of the constructed solution is sought. Repeated applications of the con-
struction procedure yields different starting solutions for the local search and the
best overall solution is kept as the result. The GRASP local search applies iterative
improvement until a locally optimal solution is found. During this phase, starting from
the current solution an improving neighbor solution is accepted and considered as the
new current solution. In this paper, we propose a variant of the GRASP framework that
uses a new ânonmonotoneâ strategy to explore the neighborhood of the current solu-
tion. We formally state the convergence of the nonmonotone local search to a locally
optimal solution and illustrate the effectiveness of the resulting Nonmonotone GRASP
on three classical hard combinatorial optimization problems: the maximum cut prob-
lem (MAX-CUT), the weighted maximum satisfiability problem (MAX-SAT), and
the quadratic assignment problem (QAP)
Anisotropic Anomalous Diffusion assessed in the human brain by scalar invariant indices
A new method to investigate anomalous diffusion in human brain is proposed.
The method has been inspired by both the stretched-exponential model proposed
by Hall and Barrick (HB) and DTI. Quantities extracted using HB method were
able to discriminate different cerebral tissues on the basis of their
complexity, expressed by the stretching exponent gamma and of the anisotropy of
gamma across different directions. Nevertheless, these quantities were not
defined as scalar invariants like mean diffusivity and fractional anisotropy,
which are eigenvalues of the diffusion tensor. We hypotesize instead that the
signal may be espressed as a simple stretched-exponential only along the
principal axes of diffusion, while in a generic direction the signal is modeled
as a combination of three different stretched-exponentials. In this way, we
derived indices to quantify both the tissue anomalous diffusion and its
anisotropy, independently of the reference frame of the experiment. We tested
and compare our new method with DTI and HB approaches applying them to 10
healty subjects brain at 3T. Our experimental results show that our parameters
are highly correlated to intrinsic local geometry when compared to HB indices.
Moreover, they offer a different kind of contrast when compared to DTI outputs.
Specifically, our indices show a higher capability to discriminate among
different areas of the corpus callosum, which are known to be associated to
different axonal densities.Comment: 21 pages, 6 figures, 2 table
Optimal Colored Threshold Visual Cryptography Schemes
Visual cryptography schemes allow the encoding of a secret image into n shares which are distributed to the participants. The shares are such that only qualified subsets of participants can visually recover the secret image. Usually the secret image consist of black and white pixels. In colored threshold visual cryptography schemes the secret image is composed of pixels taken from a given set of c colors. The pixels expansion and the contrast of a scheme are two measures of the goodness of the scheme.
In this paper, we study c-color (k,n)-threshold visual cryptography schemes and provide a characterization of contrast-optimal schemes. More specifically we prove that there exists a contrast-optimal scheme that is a member of a special set of schemes, which we call canonical schemes, and that satisfy strong symmetry properties.
Then we use canonical schemes to provide a constructive proof of optimality, with respect to the pixel expansion, of c-color (n,n)-threshold visual cryptography schemes.
Finally, we provide constructions of c-color (2,n)-threshold schemes whose pixels expansion improves on previously proposed schemes
Solar flares and their associated processes
The evolution of the solar neutrino flux which is described by the wave
function
is examined. Our treatment of the problem holds for any standard model (SM)
extensions possessing nonzero dipole magnetic and anapole moments. When the
solar neutrino flux moves through the solar flare (SF) region in the preflare
period, then it undergoes the additional (compared with the SM) resonance
conversions. As a result, the weakening the electron neutrinos flux takes
place. On the other hand, existence of the additional resonances lead to
appearance of the and neutrinos
that could be detected by the terrestrial detectors.
The hypothesis of the -induced -decays is also discussed.
According to it, before the large SF, decreasing the -decay rate for
some elements takes place. The possible influence of the electron antineutrino
flux produced in the superflares on the regime of the hypothetical georeactor
is considered.Comment: 11 pages. arXiv admin note: text overlap with arXiv:hep-ph/0401221 by
other author
Effect of gaseous ozone treatment on the aroma and clove rot by Fusarium proliferatum during garlic postharvest storage
It is known that garlic bulbs preserved with traditional methods undergo considerable losses, ranging from 25 to 40%. A frequent cause of these losses is associated with the development of pathogenic fungi, such as those of the genus Fusarium. The effect of ozone on post-harvest garlic bulbs was evaluated. Garlic cloves inoculated with Fusarium proliferatum F21 and F22 strains, were exposed to a continuous gaseous ozone flow (2.14 ÎŒg mâ3), during 4 days, 20 h a day. After ozone-treatment, the garlic samples were moved at 22 °C to mimic retail conditions (shelf life). The changes in several quality parameters such as fungal decay and aroma were evaluated on garlic samples, as whole bulbs, cloves with and without tunic, through a sensorial descriptive test, SPME analysis in GC/MS and microbiological approaches. The data collected showed that ozone treatment did not affect the aromatic profile of garlic. A significant detrimental effect of ozone treatment on garlic decay was observed. Our results encourage the use of gaseous ozone treatment for containing garlic fungal decay during its storage
Overcoming the Obfuscation of Java Programs by Identifier Renaming
Decompilation is the process of translating object code to source code and is usually the first step towards the reverse-engineering
of an application. Many obfuscation techniques and tools have been developed, with the aim of modifying a program, such that its
functionalities are preserved, while its understandability is compromised for a human reader or the decompilation is made unsuccessful.
Some approaches rely on malicious identifiers renaming, i.e., on the modification of the program identifiers in order to introduce
confusion and possibly prevent the decompilation of the code.
In this work we introduce a new technique to overcome the obfuscation of Java programs by identifier renaming. Such a technique
relies on the intelligent modification of identifiers in Java bytecode.
We present a new software tool which implements our technique and allows the processing of an obfuscated program in order to
rename the identifiers as required by our technique. Moreover, we show how to use the existing tools to provide a partial implementation
of the technique we propose.
Finally, we discuss the feasibility of our approach by showing how to contrast the obfuscation techniques based on malicious
identifier renaming recently presented in literature
Targeting leukemic stem cells in chronic myeloid leukemia: Is it worth the effort?
Chronic myeloid leukemia (CML) is a classical example of stem cell cancer since it arises in a multipotent hematopoietic stem cell upon the acquisition of the t(9;22) chromosomal transloca-tion, that converts it into a leukemic stem cell (LSC). The resulting BCRâABL1 fusion gene encodes a deregulated tyrosine kinase that is recognized as the disease driver. Therapy with tyrosine kinase inhibitors (TKIs) eliminates progenitor and more differentiated cells but fails to eradicate quiescent LSCs. Thus, although many patients obtain excellent responses and a proportion of them can even attempt treatment discontinuation (treatment free remission [TFR]) after some years of therapy, LSCs persist, and represent a potentially dangerous reservoir feeding relapse and hampering TFR. Over the past two decades, intensive efforts have been devoted to the characterization of CML LSCs and to the dissection of the cellâintrinsic and âextrinsic mechanisms sustaining their persistence, in an attempt to find druggable targets enabling LSC eradication. Here we provide an overview and an update on these mechanisms, focusing in particular on the most recent acquisitions. Moreover, we provide a critical appraisal of the clinical relevance and feasibility of LSC targeting in CML
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