9,837 research outputs found
Timed Consistent Network Updates
Network updates such as policy and routing changes occur frequently in
Software Defined Networks (SDN). Updates should be performed consistently,
preventing temporary disruptions, and should require as little overhead as
possible. Scalability is increasingly becoming an essential requirement in SDN.
In this paper we propose to use time-triggered network updates to achieve
consistent updates. Our proposed solution requires lower overhead than existing
update approaches, without compromising the consistency during the update. We
demonstrate that accurate time enables far more scalable consistent updates in
SDN than previously available. In addition, it provides the SDN programmer with
fine-grained control over the tradeoff between consistency and scalability.Comment: This technical report is an extended version of the paper "Timed
Consistent Network Updates", which was accepted to the ACM SIGCOMM Symposium
on SDN Research (SOSR) '15, Santa Clara, CA, US, June 201
The Distribution of the Asymptotic Number of Citations to Sets of Publications by a Researcher or From an Academic Department Are Consistent With a Discrete Lognormal Model
How to quantify the impact of a researcher's or an institution's body of work
is a matter of increasing importance to scientists, funding agencies, and
hiring committees. The use of bibliometric indicators, such as the h-index or
the Journal Impact Factor, have become widespread despite their known
limitations. We argue that most existing bibliometric indicators are
inconsistent, biased, and, worst of all, susceptible to manipulation. Here, we
pursue a principled approach to the development of an indicator to quantify the
scientific impact of both individual researchers and research institutions
grounded on the functional form of the distribution of the asymptotic number of
citations. We validate our approach using the publication records of 1,283
researchers from seven scientific and engineering disciplines and the chemistry
departments at the 106 U.S. research institutions classified as "very high
research activity". Our approach has three distinct advantages. First, it
accurately captures the overall scientific impact of researchers at all career
stages, as measured by asymptotic citation counts. Second, unlike other
measures, our indicator is resistant to manipulation and rewards publication
quality over quantity. Third, our approach captures the time-evolution of the
scientific impact of research institutions.Comment: 20 pages, 11 figures, 3 table
Sampling system for wheat (Triticum aestivum L) area estimation using digital LANDSAT MSS data and aerial photographs
A procedure to estimate wheat (Triticum aestivum L) area using sampling technique based on aerial photographs and digital LANDSAT MSS data is developed. Aerial photographs covering 720 square km are visually analyzed. To estimate wheat area, a regression approach is applied using different sample sizes and various sampling units. As the size of sampling unit decreased, the percentage of sampled area required to obtain similar estimation performance also decreased. The lowest percentage of the area sampled for wheat estimation with relatively high precision and accuracy through regression estimation is 13.90% using 10 square km as the sampling unit. Wheat area estimation using only aerial photographs is less precise and accurate than those obtained by regression estimation
Morphological transition between diffusion-limited and ballistic aggregation growth patterns
In this work, the transition between diffusion-limited and ballistic
aggregation models was revisited using a model in which biased random walks
simulate the particle trajectories. The bias is controlled by a parameter
, which assumes the value (1) for ballistic
(diffusion-limited) aggregation model. Patterns growing from a single seed were
considered. In order to simulate large clusters, a new efficient algorithm was
developed. For , the patterns are fractal on the small length
scales, but homogeneous on the large ones. We evaluated the mean density of
particles in the region defined by a circle of radius centered
at the initial seed. As a function of , reaches the asymptotic
value following a power law
with a universal exponent , independent of . The
asymptotic value has the behavior , where . The characteristic crossover length that determines the transition
from DLA- to BA-like scaling regimes is given by ,
where , while the cluster mass at the crossover follows a power
law , where . We deduce the
scaling relations \beta=\n u\gamma and between these
exponents.Comment: 7 pages, 8 figure
Thermostatistics of overdamped motion of interacting particles
We show through a nonlinear Fokker-Planck formalism, and confirm by molecular
dynamics simulations, that the overdamped motion of interacting particles at
T=0, where T is the temperature of a thermal bath connected to the system, can
be directly associated with Tsallis thermostatistics. For sufficiently high
values of T, the distribution of particles becomes Gaussian, so that the
classical Boltzmann-Gibbs behavior is recovered. For intermediate temperatures
of the thermal bath, the system displays a mixed behavior that follows a novel
type of thermostatistics, where the entropy is given by a linear combination of
Tsallis and Boltzmann-Gibbs entropies.Comment: 4 pages, 2 figure
Universal reduction of pressure between charged surfaces by long-wavelength surface charge modulation
We predict theoretically that long-wavelength surface charge modulations
universally reduce the pressure between the charged surfaces with counterions
compared with the case of uniformly charged surfaces with the same average
surface charge density. The physical origin of this effect is the fact that
surface charge modulations always lead to enhanced counterion localization near
the surfaces, and hence, fewer charges at the midplane. We confirm the last
prediction with Monte Carlo simulations.Comment: 8 pages 1 figure, Europhys. Lett., in pres
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