682 research outputs found
An objective based classification of aggregation techniques for wireless sensor networks
Wireless Sensor Networks have gained immense popularity in recent years due to their ever increasing capabilities and wide range of critical applications. A huge body of research efforts has been dedicated to find ways to utilize limited resources of these sensor nodes in an efficient manner. One of the common ways to minimize energy consumption has been aggregation of input data. We note that every aggregation technique has an improvement objective to achieve with respect to the output it produces. Each technique is designed to achieve some target e.g. reduce data size, minimize transmission energy, enhance accuracy etc. This paper presents a comprehensive survey of aggregation techniques that can be used in distributed manner to improve lifetime and energy conservation of wireless sensor networks. Main contribution of this work is proposal of a novel classification of such techniques based on the type of improvement they offer when applied to WSNs. Due to the existence of a myriad of definitions of aggregation, we first review the meaning of term aggregation that can be applied to WSN. The concept is then associated with the proposed classes. Each class of techniques is divided into a number of subclasses and a brief literature review of related work in WSN for each of these is also presented
Deviation of Atmospheric Mixing from Maximal and Structure in the Leptonic Flavor Sector
I attempt to quantify how far from maximal one should expect the atmospheric
mixing angle to be given a neutrino mass-matrix that leads, at zeroth order, to
a nu_3 mass-eigenstate that is 0% nu_e, 50% nu_mu, and 50% nu_tau. This is done
by assuming that the solar mass-squared difference is induced by an
"anarchical" first order perturbation, an approach than can naturally lead to
experimentally allowed values for all oscillation parameters. In particular,
both |cos 2theta_atm| (the measure for the deviation of atmospheric mixing from
maximal) and |U_e3| are of order sqrt(Delta m^2_sol/Delta m^2_atm) in the case
of a normal neutrino mass-hierarchy, or of order Delta m^2_sol/Delta m^2_atm in
the case of an inverted one. Hence, if any of the textures analyzed here has
anything to do with reality, next-generation neutrino experiments can see a
nonzero cos 2theta_atm in the case of a normal mass-hierarchy, while in the
case of an inverted mass-hierarchy only neutrino factories should be able to
see a deviation of sin^2 2theta_atm from 1.Comment: 12 pages, no figures, references and acknowledgments adde
Punctuated equilibria and 1/f noise in a biological coevolution model with individual-based dynamics
We present a study by linear stability analysis and large-scale Monte Carlo
simulations of a simple model of biological coevolution. Selection is provided
through a reproduction probability that contains quenched, random interspecies
interactions, while genetic variation is provided through a low mutation rate.
Both selection and mutation act on individual organisms. Consistent with some
current theories of macroevolutionary dynamics, the model displays
intermittent, statistically self-similar behavior with punctuated equilibria.
The probability density for the lifetimes of ecological communities is well
approximated by a power law with exponent near -2, and the corresponding power
spectral densities show 1/f noise (flicker noise) over several decades. The
long-lived communities (quasi-steady states) consist of a relatively small
number of mutualistically interacting species, and they are surrounded by a
``protection zone'' of closely related genotypes that have a very low
probability of invading the resident community. The extent of the protection
zone affects the stability of the community in a way analogous to the height of
the free-energy barrier surrounding a metastable state in a physical system.
Measures of biological diversity are on average stationary with no discernible
trends, even over our very long simulation runs of approximately 3.4x10^7
generations.Comment: 20 pages RevTex. Minor revisions consistent with published versio
Self-optimization, community stability, and fluctuations in two individual-based models of biological coevolution
We compare and contrast the long-time dynamical properties of two
individual-based models of biological coevolution. Selection occurs via
multispecies, stochastic population dynamics with reproduction probabilities
that depend nonlinearly on the population densities of all species resident in
the community. New species are introduced through mutation. Both models are
amenable to exact linear stability analysis, and we compare the analytic
results with large-scale kinetic Monte Carlo simulations, obtaining the
population size as a function of an average interspecies interaction strength.
Over time, the models self-optimize through mutation and selection to
approximately maximize a community fitness function, subject only to
constraints internal to the particular model. If the interspecies interactions
are randomly distributed on an interval including positive values, the system
evolves toward self-sustaining, mutualistic communities. In contrast, for the
predator-prey case the matrix of interactions is antisymmetric, and a nonzero
population size must be sustained by an external resource. Time series of the
diversity and population size for both models show approximate 1/f noise and
power-law distributions for the lifetimes of communities and species. For the
mutualistic model, these two lifetime distributions have the same exponent,
while their exponents are different for the predator-prey model. The difference
is probably due to greater resilience toward mass extinctions in the food-web
like communities produced by the predator-prey model.Comment: 26 pages, 12 figures. Discussion of early-time dynamics added. J.
Math. Biol., in pres
Neutralino Dark Matter, b-tau Yukawa Unification and Non-Universal Sfermion Masses
We study the implications of minimal non-Universal Boundary Conditions in the
sfermion Soft SUSY Breaking (SSB) masses of mSUGRA. We impose asymptotic b-tau
Yukawa coupling Unification and we resort to a parameterization of the
deviation from Universality in the SSB motivated by the multiplet structure of
SU(5) GUT. A set of cosmo-phenomenological constraints, including the recent
results from WMAP, determines the allowed parameter space of the models under
consideration. We highlight a new coannihilation corridor where
neutralino-sbottom and neutralino-tau sneutrino-stau coannihilations
significantly contribute to the reduction of the neutralino relic density.Comment: 38 pages, 27 Figures, Latex; Version accepted for publication in PR
Superhard Phases of Simple Substances and Binary Compounds of the B-C-N-O System: from Diamond to the Latest Results (a Review)
The basic known and hypothetic one- and two-element phases of the B-C-N-O
system (both superhard phases having diamond and boron structures and
precursors to synthesize them) are described. The attention has been given to
the structure, basic mechanical properties, and methods to identify and
characterize the materials. For some phases that have been recently described
in the literature the synthesis conditions at high pressures and temperatures
are indicated.Comment: Review on superhard B-C-N-O phase
A Model for the Development of the Rhizobial and Arbuscular Mycorrhizal Symbioses in Legumes and Its Use to Understand the Roles of Ethylene in the Establishment of these two Symbioses
We propose a model depicting the development of nodulation and arbuscular mycorrhizae. Both processes are dissected into many steps, using Pisum sativum L. nodulation mutants as a guideline. For nodulation, we distinguish two main developmental programs, one epidermal and one cortical. Whereas Nod factors alone affect the cortical program, bacteria are required to trigger the epidermal events. We propose that the two programs of the rhizobial symbiosis evolved separately and that, over time, they came to function together. The distinction between these two programs does not exist for arbuscular mycorrhizae development despite events occurring in both root tissues. Mutations that affect both symbioses are restricted to the epidermal program. We propose here sites of action and potential roles for ethylene during the formation of the two symbioses with a specific hypothesis for nodule organogenesis. Assuming the epidermis does not make ethylene, the microsymbionts probably first encounter a regulatory level of ethylene at the epidermisâoutermost cortical cell layer interface. Depending on the hormone concentrations there, infection will either progress or be blocked. In the former case, ethylene affects the cortex cytoskeleton, allowing reorganization that facilitates infection; in the latter case, ethylene acts on several enzymes that interfere with infection thread growth, causing it to abort. Throughout this review, the difficulty of generalizing the roles of ethylene is emphasized and numerous examples are given to demonstrate the diversity that exists in plants
Search for lepton-flavor violation at HERA
A search for lepton-flavor-violating interactions and has been performed with the ZEUS detector using the entire HERA I
data sample, corresponding to an integrated luminosity of 130 pb^{-1}. The data
were taken at center-of-mass energies, , of 300 and 318 GeV. No
evidence of lepton-flavor violation was found, and constraints were derived on
leptoquarks (LQs) that could mediate such interactions. For LQ masses below
, limits were set on , where
is the coupling of the LQ to an electron and a
first-generation quark , and is the branching ratio of
the LQ to the final-state lepton ( or ) and a quark . For
LQ masses much larger than , limits were set on the four-fermion
interaction term for LQs that couple to an electron and a quark
and to a lepton and a quark , where and are
quark generation indices. Some of the limits are also applicable to
lepton-flavor-violating processes mediated by squarks in -Parity-violating
supersymmetric models. In some cases, especially when a higher-generation quark
is involved and for the process , the ZEUS limits are the most
stringent to date.Comment: 37 pages, 10 figures, Accepted by EPJC. References and 1 figure (Fig.
6) adde
Multijet production in neutral current deep inelastic scattering at HERA and determination of alpha_s
Multijet production rates in neutral current deep inelastic scattering have
been measured in the range of exchanged boson virtualities 10 < Q2 < 5000 GeV2.
The data were taken at the ep collider HERA with centre-of-mass energy sqrt(s)
= 318 GeV using the ZEUS detector and correspond to an integrated luminosity of
82.2 pb-1. Jets were identified in the Breit frame using the k_T cluster
algorithm in the longitudinally invariant inclusive mode. Measurements of
differential dijet and trijet cross sections are presented as functions of jet
transverse energy E_{T,B}{jet}, pseudorapidity eta_{LAB}{jet} and Q2 with
E_{T,B}{jet} > 5 GeV and -1 < eta_{LAB}{jet} < 2.5. Next-to-leading-order QCD
calculations describe the data well. The value of the strong coupling constant
alpha_s(M_Z), determined from the ratio of the trijet to dijet cross sections,
is alpha_s(M_Z) = 0.1179 pm 0.0013(stat.) {+0.0028}_{-0.0046}(exp.)
{+0.0064}_{-0.0046}(th.)Comment: 22 pages, 5 figure
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