6,967 research outputs found
Aspects of the biology of the lagoon crab Callinectes amnicola (Derocheburne) in Badagry, Lagos and Lekki lagoons, Nigeria
A preliminary report of the size, composition, growth pattern and food habits of the blue crab, Callinectes amnicola, (De Rocheburne) in the Badagry, Lagos and Lekki Lagoons (Nigeria) is presented. The collection of crabs from the three lagoons covered the period from May 1999 to October 2000. The carapace length for Badagry Lagoon ranged from 2.2 cm to 16.4 cm with weight of 4.4 g to 252.6 g. The crabs showed a unimodal size distribution. For the Lagos Lagoon, crabs sizes ranged from 3.5 cm to 16.8 cm and weighed 3.28 to 277.1 g. The sizes of crabs in the Lekki Lagoon ranged from 3.5 cm to 16.1 cm and weighed 3.5 g to 262.7 g. Crabs from the three lagoons exhibited negative allometric growth. The food items were similar in the three lagoons and comprised mainly mollusc shells, fish parts, shrimps and crab appendages and occasionally higher plant material
Heisenberg modules as function spaces
Let be a closed, cocompact subgroup of , where
is a second countable, locally compact abelian group. Using localization of
Hilbert -modules, we show that the Heisenberg module
over the twisted group -algebra
due to Rieffel can be continuously and densely embedded into the Hilbert space
. This allows us to characterize a finite set of generators for
as exactly the generators of multi-window
(continuous) Gabor frames over , a result which was previously known
only for a dense subspace of . We show that
as a function space satisfies two properties that
make it eligible for time-frequency analysis: Its elements satisfy the
fundamental identity of Gabor analysis if is a lattice, and their
associated frame operators corresponding to are bounded.Comment: 24 pages; several changes have been made to the presentation, while
the content remains essentially unchanged; to appear in Journal of Fourier
Analysis and Application
An early warning system for multivariate time series with sparse and non-uniform sampling
In this paper we propose a new early warning test statistic, the ratio of
deviations (RoD), which is defined to be the root mean squared of successive
differences divided by the standard deviation. We show that RoD and
autocorrelation are asymptotically related, and this relationship motivates the
use of RoD to predict Hopf bifurcations in multivariate systems before they
occur. We validate the use of RoD on synthetic data in the novel situation
where the data is sparse and non-uniformly sampled. Additionally, we adapt the
method to be used on high-frequency time series by sampling, and demonstrate
the proficiency of RoD as a classifier.Comment: 14 pages, 8 figure
Gabor Duality Theory for Morita Equivalent -algebras
The duality principle for Gabor frames is one of the pillars of Gabor
analysis. We establish a far-reaching generalization to Morita equivalent
-algebras where the equivalence bimodule is a finitely generated
projective Hilbert -module. These Hilbert -modules are equipped with
some extra structure and are called Gabor bimodules. We formulate a duality
principle for standard module frames for Gabor bimodules which reduces to the
well-known Gabor duality principle for twisted group -algebras of a
lattice in phase space. We lift all these results to the matrix algebra level
and in the description of the module frames associated to a matrix Gabor
bimodule we introduce -matrix frames, which generalize superframes and
multi-window frames. Density theorems for -matrix frames are
established, which extend the ones for multi-window and super Gabor frames. Our
approach is based on the localization of a Hilbert -module with respect to
a trace.Comment: 36 page
Training-Embedded, Single-Symbol ML-Decodable, Distributed STBCs for Relay Networks
Recently, a special class of complex designs called Training-Embedded Complex
Orthogonal Designs (TE-CODs) has been introduced to construct single-symbol
Maximum Likelihood (ML) decodable (SSD) distributed space-time block codes
(DSTBCs) for two-hop wireless relay networks using the amplify and forward
protocol. However, to implement DSTBCs from square TE-CODs, the overhead due to
the transmission of training symbols becomes prohibitively large as the number
of relays increase. In this paper, we propose TE-Coordinate Interleaved
Orthogonal Designs (TE-CIODs) to construct SSD DSTBCs. Exploiting the block
diagonal structure of TE-CIODs, we show that, the overhead due to the
transmission of training symbols to implement DSTBCs from TE-CIODs is smaller
than that for TE-CODs. We also show that DSTBCs from TE-CIODs offer higher rate
than those from TE-CODs for identical number of relays while maintaining the
SSD and full-diversity properties.Comment: 7 pages, 2 figure
Non-atomic Games for Multi-User Systems
In this contribution, the performance of a multi-user system is analyzed in
the context of frequency selective fading channels. Using game theoretic tools,
a useful framework is provided in order to determine the optimal power
allocation when users know only their own channel (while perfect channel state
information is assumed at the base station). We consider the realistic case of
frequency selective channels for uplink CDMA. This scenario illustrates the
case of decentralized schemes, where limited information on the network is
available at the terminal. Various receivers are considered, namely the Matched
filter, the MMSE filter and the optimum filter. The goal of this paper is to
derive simple expressions for the non-cooperative Nash equilibrium as the
number of mobiles becomes large and the spreading length increases. To that end
two asymptotic methodologies are combined. The first is asymptotic random
matrix theory which allows us to obtain explicit expressions of the impact of
all other mobiles on any given tagged mobile. The second is the theory of
non-atomic games which computes good approximations of the Nash equilibrium as
the number of mobiles grows.Comment: 17 pages, 4 figures, submitted to IEEE JSAC Special Issue on ``Game
Theory in Communication Systems'
- …