5,031 research outputs found
Network attack detection at flow level
In this paper, we propose a new method for detecting unauthorized network
intrusions, based on a traffic flow model and Cisco NetFlow protocol
application. The method developed allows us not only to detect the most common
types of network attack (DDoS and port scanning), but also to make a list of
trespassers' IP-addresses. Therefore, this method can be applied in intrusion
detection systems, and in those systems which lock these IP-addresses
Why is solar cycle 24 an inefficient producer of high-energy particle events?
The aim of the study is to investigate the reason for the low productivity of
high-energy SEPs in the present solar cycle. We employ scaling laws derived
from diffusive shock acceleration theory and simulation studies including
proton-generated upstream Alfv\'en waves to find out how the changes observed
in the long-term average properties of the erupting and ambient coronal and/or
solar wind plasma would affect the ability of shocks to accelerate particles to
the highest energies. Provided that self-generated turbulence dominates
particle transport around coronal shocks, it is found that the most crucial
factors controlling the diffusive shock acceleration process are the number
density of seed particles and the plasma density of the ambient medium.
Assuming that suprathermal populations provide a fraction of the particles
injected to shock acceleration in the corona, we show that the lack of most
energetic particle events as well as the lack of low charge-to-mass ratio ion
species in the present cycle can be understood as a result of the reduction of
average coronal plasma and suprathermal densities in the present cycle over the
previous one
Xi and AntiXi production in Pb+Pb collisions at 40 AGeV at CERN SPS
First results on the production of Xi and AntiXi hyperons in Pb+Pb
interactions at 40 AGeV are presented. The AntiXi/Xi ratio at midrapidity is
studied as a function of collision centrality. The ratio shows no significant
centrality dependence within statistical errors; it ranges from 0.07 to 0.15.
The AntiXi/Xi ratio for central Pb+Pb collisions increases strongly with the
collision energy.Comment: 6 pages, 6 figures, proceedings of SQM03, to be published in Journal
of Physics G; V2: changes in table 1 and figure
Methods to study event-by-event fluctuations in the NA61/SHINE experiment at the CERN SPS
Theoretical calculations locate the critical point of strongly interacting
matter (CP) at energies accessible at the CERN SPS. Event-by-event transverse
momentum and multiplicity fluctuations are considered as one of the most
important tools to search for the CP. Pilot studies of the energy dependence
and the system size dependence of both and multiplicity fluctuations were
performed by the NA49 experiment. The NA61/SHINE ion program is a continuation
of these efforts. After briefly recalling the essential NA49 results on
fluctuations we will discuss the technical methods (removing Non-Target
interactions) which we plan to apply for future transverse momentum and
multiplicity fluctuation analyses.Comment: Proceedings of CPOD 2010, 23-29 August, JINR, Dubn
Omega and AntiOmega production in Pb+Pb and p+p collisions at 30, 40 and 158 AGeV
We report preliminary results on Omega and AntiOmega production in central
Pb+Pb collisions at 30, 40 and 158 AGeV and p + p interactions at 158 GeV. The
midrapidity AntiOmega/Omega ratio is estimated to be 0.45 +- 0.05 and 0.41 +-
0.18 for central Pb+Pb collisions at 158 and 40 AGeV, respectively. The
corresponding value for 158 GeV p+p interactions is 0.67 +- 0.62. For central
Pb+Pb collisions at 158 AGeV fully corrected distributions are obtained. The
inverse slope parameters of the transverse mass spectrum and total yields are
T(Omega) = 276 +- 23 MeV, = 0.47 +- 0.07 and T(AntiOmega) = 285 +- 39
MeV, = 0.15 +- 0.02.Comment: Contribution to the proceedings of "Strangeness in Quark Matter 2003"
(March 2003, Atlantic Beach NC, USA), to be published in Journal of Physics
G., 6 pages, 6 figure
Status and plans of the ion program of NA61 at the CERN SPS
The NA61/SHINE at the CERN SPS is a new experiment to study hadron production
in p+p p+A, h+A and A+A interactions. The main goal of the NA61 ion program is
to explore the phase diagram (T - mu_B) of strongly interacting matter. In
particular, we plan to study the properties of the onset of deconfinement and
to search for the signatures of the critical point. A two-dimensional scan of
the phase diagram will be performed by varying the energy (13A-158A GeV) and
system size (p+p, Be+Be, Ar+Ca, Xe+La) of collisions. This paper summarizes the
status and plans of the NA61/SHINE ion program. In particular the detector
upgrades, data taking schedule and the first results on spectra and
correlations are discussed.Comment: Proceedings of "Critical Point and Onset of Deconfinement - CPOD
2011", Wuhan, November 7-11, 2011, version accepted by Central European
Journal of Physic
A new Luminous Variable in M33
We present a new luminous star in M33 located in the nuclear region. The star
shows strong FeII and [FeII] forest, hydrogen emissions in the spectrum, as
well as nebular lines. TiII and SiII lines were detected in absorption, their
radial velocity shifted by ~ -30km/s relative to emission lines. The star is
variable over seven years with 0.5 mag variations over a year. We studied its
spectral energy distribution together with five confirmed Luminous Blue
Variables and Var A in M33 using homogeneous data and methods. We found the
star's bolometric luminosity to be log(L/Lsun)~6.27, a surface temperature of
T~16000K and black body temperatures of two dust components of T~900 and 420K.
The new star has properties intermediate between the LBVs and VarA (probable
cool hypergiant). In the same time it has a hot photosphere, LBV-like
luminosity and an extensive circumstellar material (strong [CaII] lines). In
these seven luminous variables in M33 we find the total range of the hot
component luminosities is 1.0 dex, but that of the dust componets is 2.0 dex.
We conclude that the dust phenomenon in the luminous variables is temporary and
variable, and that dust activity may follow strong eruptions.Comment: 5 pages, 6 figures; MNRAS Letter accepte
Chemical equilibrium study at SPS 158A GeV
A detailed study of chemical freeze-out in nucleus-nucleus collisions at beam
energy 158A GeV is presented. By analyzing hadronic multiplicities within the
statistical hadronization approach, the chemical equilibration of p-p, C-C,
Si-Si and Pb-Pb systems is studied as a function of the number of participating
nucleons in the system. Additionally, Two Component statistical hadronization
model is applied to the data and is found to be able to explain the observed
strangeness hadronic phase space under-saturation.Comment: 4 pages, 3 figures to appear in the proceedings of the ''Strangeness
in Quark Matter 2004'' conferenc
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