1,666 research outputs found
Stationary and Mobile Target Detection using Mobile Wireless Sensor Networks
In this work, we study the target detection and tracking problem in mobile
sensor networks, where the performance metrics of interest are probability of
detection and tracking coverage, when the target can be stationary or mobile
and its duration is finite. We propose a physical coverage-based mobility
model, where the mobile sensor nodes move such that the overlap between the
covered areas by different mobile nodes is small. It is shown that for
stationary target scenario the proposed mobility model can achieve a desired
detection probability with a significantly lower number of mobile nodes
especially when the detection requirements are highly stringent. Similarly,
when the target is mobile the coverage-based mobility model produces a
consistently higher detection probability compared to other models under
investigation.Comment: 7 pages, 12 figures, appeared in INFOCOM 201
Networking Behavior in Thin Film and Nanostructure Growth Dynamics
Thin film coatings have been essential in development of several micro and
nano-scale devices. To realize thin film coatings various deposition techniques
are employed, each yielding surface morphologies with different characteristics
of interest. Therefore, understanding and control of the surface growth is of
great interest. In this paper, we devise a novel network-based modeling of the
growth dynamics of such thin films and nano-structures. We specifically map
dynamic steps taking place during the growth to components (e.g., nodes, links)
of a corresponding network. We present initial results showing that this
network-based modeling approach to the growth dynamics can simplify our
understanding of the fundamental physical dynamics such as shadowing and
re-emission effects
Focused Azimuthally Polarized Vector Beam and Spatial Magnetic Resolution below the Diffraction Limit
An azimuthally electric-polarized vector beam (APB), with a polarization
vortex, has a salient feature that it contains a magnetic-dominant region
within which electric field ideally has a null while longitudinal magnetic
field is maximum. Fresnel diffraction theory and plane-wave spectral (PWS)
calculations are applied to quantify field features of such a beam upon
focusing through a lens. The diffraction-limited full width at half maximum
(FWHM) of the beam's longitudinal magnetic field intensity profile and
complementary FWHM (CFWHM) of the beam's annular-shaped total electric field
intensity profile are examined at the lens's focal plane as a function of the
lens's paraxial focal distance. Then, we place a subwavelength dense dielectric
Mie scatterer in the minimum-waist plane of a self-standing converging APB and
demonstrate for the first time that a very high resolution magnetic field at
optical frequency is achieved with total magnetic field FWHM of 0.23{\lambda}
(i.e., magnetic field spot area of 0.04{\lambda}^2) within a magnetic-dominant
region. The theory shown here is valuable for development of optical microscopy
and spectroscopy systems based on magnetic dipolar transitions which are in
general much weaker than their electric counterparts
Electronic shells of Dirac fermions in graphene quantum rings in a magnetic field
We present results of tight binding calculations demonstrating existence of
degenerate electronic shells of Dirac Fermions in narrow, charge neutral
graphene quantum rings. We predict removal of degeneracy with finite magnetic
field. We show, using a combination of tight binding and configuration
interaction methods, that by filling a graphene ring with additional electrons
this carbon based structure with half-filled shell acquires a finite magnetic
moment.Comment: 10 pages, 4 figure
Theory of a Directive Optical Leaky Wave Antenna Integrated into a Resonator and Enhancement of Radiation Control
We provide for the first time the detailed study of the radiation performance
of an optical leaky wave antenna (OLWA) integrated into a Fabry-P\'erot
resonator. We show that the radiation pattern can be expressed as the one
generated by the interference of two leaky waves counter-propagating in the
resonator leading to a design procedure for achieving optimized broadside
radiation, i.e., normal to the waveguide axis. We thus report a realizable
implementation of the OLWA made of semiconductor and dielectric regions. The
theoretical modeling is supported by full-wave simulation results, which are
found to be in good agreement. We aim to control the radiation intensity in the
broadside direction via excess carrier generation in the semiconductor regions.
We show that the presence of the resonator can provide an effective way of
enhancing the radiation level modulation, which reaches values as high as 13.5
dB, paving the way for novel promising control capabilities that might allow
the generation of very fast optical switches, as an example.Comment: 10 pages, 14 figure
Graphene-Dielectric Composite Metamaterials: Evolution from Elliptic to Hyperbolic Wavevector Dispersion and The Transverse Epsilon-Near-Zero Condition
We investigated a multilayer graphene-dielectric composite material,
comprising graphene sheets separated by subwavelength-thick dielectric spacer,
and found it to exhibit hyperbolic isofrequency wavevector dispersion at far-
and mid-infrared frequencies allowing propagation of waves that would be
otherwise evanescent in a dielectric. Electrostatic biasing was considered for
tunable and controllable transition from hyperbolic to elliptic dispersion. We
explored the validity and limitation of the effective medium approximation
(EMA) for modeling wave propagation and cutoff of the propagating spatial
spectrum due to the Brillouin zone edge. We found that EMA is capable of
predicting the transition of the isofrequency dispersion diagram under certain
conditions. The graphene-based composite material allows propagation of
backward waves under the hyperbolic dispersion regime and of forward waves
under the elliptic regime. Transition from hyperbolic to elliptic dispersion
regimes is governed by the transverse epsilon-near-zero (TENZ) condition, which
implies a flatter and wider propagating spectrum with higher attenuation, when
compared to the hyperbolic regime. We also investigate the tunable transparency
of the multilayer at that condition in contrast to other materials exhibiting
ENZ phenomena.Comment: to be published in Journal of Nanophotonic
Population structure of killifish, Aphanius anatoliae (Cyprinodontidae) endemic to Anatolia in Lake Eğirdir-Isparta (Turkey)
The population structure of Aphanius anatoliae in Lake Eğirdir-Isparta-Turkey was studied, using 522 fish monthly in 2008. This study were observed in the number of individuals of each sex, age, weight and size compositions. In addition, the total length-weight relationship was calculated as well as the Von Bertalanffy growth equation. A study of the food uptake throughout the year has been carried by examination of the content of the digestive track. Males made up 51.92%, and females 48.08% of the population. The length-weight relationship and Von Bertalanffy growth equation were estimated as W= 0.0232 e ^0.098L, r=0.8262, Lt = 54.51(1 – e ^–0.279(t+1.345)), respectively. Bacillariophyta, Gammarus pulex and aquatic insecta are the major food items for Aphanius anatoliae
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