5,992 research outputs found
Food and feeding habit of a penaeid prawn Metapeneopsis stridulans (Alcock 1905)
Metapeneopsis stridulans feeds on a variety of food items, viz. diatoms, foraminiferans
polychaetes, molluscs, crustaceans and detritus consisting of unidentifiable decaying matter
along with sand and mud. The species does not show a preference for any particular food
item. There is no significant difference in the food habits among the various size groups
observed in the prawn. Monthwise feeding intensity for males and females shows males
with empty stomach to be prevalent in most months
Density Evolution for Asymmetric Memoryless Channels
Density evolution is one of the most powerful analytical tools for
low-density parity-check (LDPC) codes and graph codes with message passing
decoding algorithms. With channel symmetry as one of its fundamental
assumptions, density evolution (DE) has been widely and successfully applied to
different channels, including binary erasure channels, binary symmetric
channels, binary additive white Gaussian noise channels, etc. This paper
generalizes density evolution for non-symmetric memoryless channels, which in
turn broadens the applications to general memoryless channels, e.g. z-channels,
composite white Gaussian noise channels, etc. The central theorem underpinning
this generalization is the convergence to perfect projection for any fixed size
supporting tree. A new iterative formula of the same complexity is then
presented and the necessary theorems for the performance concentration theorems
are developed. Several properties of the new density evolution method are
explored, including stability results for general asymmetric memoryless
channels. Simulations, code optimizations, and possible new applications
suggested by this new density evolution method are also provided. This result
is also used to prove the typicality of linear LDPC codes among the coset code
ensemble when the minimum check node degree is sufficiently large. It is shown
that the convergence to perfect projection is essential to the belief
propagation algorithm even when only symmetric channels are considered. Hence
the proof of the convergence to perfect projection serves also as a completion
of the theory of classical density evolution for symmetric memoryless channels.Comment: To appear in the IEEE Transactions on Information Theor
Inhomogeneous vortex-state-driven enhancement of superconductivity in nanoengineered ferromagnet-superconductor heterostructures
Thin film heterostructures provide a powerful means to study the antagonism
between superconductivity (SC) and ferromagnetism (FM). One interesting issue
in FM-SC hybrids which defies the notion of antagonistic orders is the
observation of magnetic field induced superconductivity (FIS). Here we show
that in systems where the FM domains/islands produce spatial inhomogeneities of
the SC order parameter, the FIS can derive significant contribution from
different mobilities of the magnetic flux identified by two distinct critical
states in the inhomogeneous superconductor. Our experiments on nanoengineered
bilayers of ferromagnetic CoPt and superconducting NbN where CoPt/NbN islands
are separated by a granular NbN, lend support to this alternative explanation
of FIS in certain class of FM-SC hybrids.Comment: 5 figure
Fractional vortices in the XY model with bonds
We define a new set of excitations in the XY model which we call ``fractional
vortices''. In the frustrated XY model containing bonds, we make the
ansatz that the ground state configurations can be characterized by pairs of
oppositely charged fractional vortices. For a chain of bonds, the ground
state energy and the phase configurations calculated on the basis of this
ansatz agree well with the results from direct numerical simulations. Finally,
we discuss the possible connection of these results to some recent experiments
by Kirtley {\it et al} [Phys. Rev. B {\bf 51}, R12057 (1995)] on high-T
superconductors where fractional flux trapping was observed along certain grain
boundaries.Comment: 13 pages, 14 figures included (.eps). No essential differences to
previous version, however more compact forma
Fatigue of notched fiber composite laminates. Part 2: Analytical and experimental evaluation
The analytical/experimental correlation study was performed to develop an understanding of the behavior of notched Boron/epoxy laminates subjected to tension/tension fatigue loading. It is postulated that the fatigue induced property changes (stiffness as well as strength) of the laminate can be obtained from the lamina fatigue properties. To that end, the Boron/epoxy lamina static and fatigue data (lifetime, residual stiffness and strength) were obtained initially. The longitudinal and transverse tension data were determined from the (0) and (90) laminate tests while the in-plane shear data were obtained from the (+ or - 45) sub s laminates. The static tests obtained the notched strength and mode of failure while the fatigue tests determined lifetime, damage propagation and residual strength. The failure in static tension occurred in a transverse crack propagation mode
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