13,150 research outputs found
Hierarchical Design Based Intrusion Detection System For Wireless Ad hoc Network
In recent years, wireless ad hoc sensor network becomes popular both in civil
and military jobs. However, security is one of the significant challenges for
sensor network because of their deployment in open and unprotected environment.
As cryptographic mechanism is not enough to protect sensor network from
external attacks, intrusion detection system needs to be introduced. Though
intrusion prevention mechanism is one of the major and efficient methods
against attacks, but there might be some attacks for which prevention method is
not known. Besides preventing the system from some known attacks, intrusion
detection system gather necessary information related to attack technique and
help in the development of intrusion prevention system. In addition to
reviewing the present attacks available in wireless sensor network this paper
examines the current efforts to intrusion detection system against wireless
sensor network. In this paper we propose a hierarchical architectural design
based intrusion detection system that fits the current demands and restrictions
of wireless ad hoc sensor network. In this proposed intrusion detection system
architecture we followed clustering mechanism to build a four level
hierarchical network which enhances network scalability to large geographical
area and use both anomaly and misuse detection techniques for intrusion
detection. We introduce policy based detection mechanism as well as intrusion
response together with GSM cell concept for intrusion detection architecture.Comment: 16 pages, International Journal of Network Security & Its
Applications (IJNSA), Vol.2, No.3, July 2010. arXiv admin note: text overlap
with arXiv:1111.1933 by other author
Cylindrically symmetric wormholes
This paper discusses traversable wormholes that differ slightly but
significantly from those of the Morris-Thorne type under the assumption of
cylindrical symmetry. The throat is a piecewise smooth cylindrical surface
resulting in a shape function that is not differentiable at some value. It is
proposed that the regular derivative be replaced by a one-sided derivative at
this value. The resulting wormhole geometry satisfies the weak energy
condition.Comment: Supplied missing figures; 15 pages AMSTe
Possible existence of wormholes in the galactic halo region
Two observational results, the density profile from simulations performed in
the CDM scenario and the observed flat galactic rotation curves, are
taken as input with the aim of showing that the galactic halo possesses some of
the characteristics needed to support traversable wormholes. This result should
be sufficient to provide an incentive for scientists to seek observational
evidence for wormholes in the galactic halo region.Comment: 11 pages, 3 figures, 1 table, Eur. Phys. J. C (2014) 74:2750, DOI
10.1140/epjc/s10052-014-2750-
The formation of molecular hydrogen in the interstellar medium
H2 is the most abundant molecule in the interstellar medium and forms on the
surface of interstellar dust grains. Laboratory studies have been conducted of HD
formation on a dust grain analogue, which is a highly-oriented pyrolytic graphite
surface held at 15 K, under ultra-high vacuum. The molecules desorb from the
surface in a distribution of ro-vibrational states, which are probed using Resonance
Enhanced Multi-Photon Ionization Spectroscopy. HD in a particular ro-vibrational
state is ionized using laser photons detected by a time-of-flight mass spectrometer.
The HD+ ion yields are then data processed to obtain the relative rotational
populations of HD formed within one vibrational level and an average rotational
temperature can be found. In this thesis, HD formed in vibrational states v = 3 – 7
have been studied. This carries on from previous studies of HD and H2 in the v = 1
and 2 states. Within each vibrational level, the most populated rotational state was
found to be J = 1 or 2. The most populated vibrational state was found to be v = 4.
The HD experimental results were extrapolated to give the relative ro-vibrational
population distribution of nascent H2, which provides a new model for the
formation pumping of H2. This new formation pumping model has been
implemented into a radiative transfer code, written by Casu and Cecchi-Pestellini,
which takes into account formation, radiative and collisional pumping mechanisms
to calculate the total population distribution of H2 in an interstellar cloud and to
generate H2 spectra. The sensitivity of the H2 spectra to the physical conditions of
interstellar dark clouds, such as cloud density and temperature, has been
investigated. H2 spectra generated using the new experimentally-derived formation
pumping model has also been compared to H2 spectra generated using other
established, theoretically-derived formation pumping models
Self-interest and organizational performance: an empirical examination with U.S. and Brazilian managers
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