3,988 research outputs found
Self-Similarity in a multi-stage queueing ATM switch fabric
Recent studies of digital network traffic have shown that arrival processes in such an environment are more accurately modeled as a statistically self-similar process, rather than as a Poisson-based one. We present a simulation of a combination sharedoutput queueing ATM switch fabric, sourced by two models of self-similar input. The effect of self-similarity on the average queue length and cell loss probability for this multi-stage queue is examined for varying load, buffer size, and internal speedup. The results using two self-similar input models, Pareto-distributed interarrival times and a Poisson-Zeta ON-OFF model, are compared with each other and with results using Poisson interarrival times and an ON-OFF bursty traffic source with Ge ometrically distributed burst lengths. The results show that at a high utilization and at a high degree of self-similarity, switch performance improves slowly with increasing buffer size and speedup, as compared to the improvement using Poisson-based traffic
Submillimeter Spectrum of Formic Acid
We have measured new submillimeter-wave data around 600 GHz and around 1.1
THz for the 13C isotopologue of formic acid and for the two deuterium
isotopomers; in each case for both the trans and cis rotamer. For cis-DCOOH and
cis-HCOOD in particular only data up to 50 GHz was previously available. For
all species the quality and quantity of molecular parameters has been increased
providing new measured frequencies and more precise and reliable frequencies in
the range of existing and near-future submillimeter and far-infrared
astronomical spectroscopy instruments such as Herschel, SOFIA and ALMA
Hot tempers can help cool the planet
When conveyed in a bipartisan fashion, collective anger can be a powerful unifier across partisan divisions. Anandita Sabherwal, Adam Pearson, and Gregg Sparkman write that, by expressing their anger, activists can turn individuals who may be sitting at home stewing into a collective that is emboldened to act. Despite our differences, our anger reflects our shared values, and a shared desire for a more sustainable future
X-type and Y-type junction stability in domain wall networks
We develop an analytic formalism that allows one to quantify the stability
properties of X-type and Y-type junctions in domain wall networks in two
dimensions. A similar approach might be applicable to more general defect
systems involving junctions that appear in a range of physical situations, for
example, in the context of F- and D-type strings in string theory. We apply
this formalism to a particular field theory, Carter's pentavac model, where the
strength of the symmetry breaking is governed by the parameter .
We find that for low values of the symmetry breaking parameter X-type junctions
will be stable, whereas for higher values an X-type junction will separate into
two Y-type junctions. The critical angle separating the two regimes is given by
\alpha_c = 293^{\circ}\sqrt{|\epsilon|} and this is confirmed using simple
numerical experiments. We go on to simulate the pentavac model from random
initial conditions and we find that the dominant junction is of \ytype for
|\epsilon| \geq 0.02 and is of \xtype for |\epsilon| \leq 0.02\epsilon\qsubrm{N}{dw}\propto
t^{-1}\epsilont^{-1}$ lore.Comment: 24 pages, 13 figures; typos fixe
Using remote, spatial techniques to select a random household sample in a dispersed, semi-nomadic pastoral community: utility for a longitudinal health and demographic surveillance system
Constraining dark sector perturbations 1: cosmic shear and CMB lensing
We present current and future constraints on equations of state for dark sector perturbations. The equations of state considered are those corresponding to a generalized scalar field model and time-diffeomorphism invariant Script L(g) theories that are equivalent to models of a relativistic elastic medium and also Lorentz violating massive gravity. We develop a theoretical understanding of the observable impact of these models. In order to constrain these models we use CMB temperature data from Planck, BAO measurements, CMB lensing data from Planck and the South Pole Telescope, and weak galaxy lensing data from CFHTLenS. We find non-trivial exclusions on the range of parameters, although the data remains compatible with w=−1. We gauge how future experiments will help to constrain the parameters. This is done via a likelihood analysis for CMB experiments such as CoRE and PRISM, and tomographic galaxy weak lensing surveys, focussing in on the potential discriminatory power of Euclid on mildly non-linear scales
Social Psychology and Neuroscience: Strange Bedfellows or a Healthy Marriage?
In this paper, we assess what neuroscience theory and method have contributed to the study of group processes and intergroup relations and what we see as potential future contributions to the discipline. We briefly review the historical relation between neuroscience and social psychology, identify issues that may limit the value of neuroscience to the study of group processes and relations, and then argue that social neuroscience indeed holds significant promise for understanding many key elements of group processes and intergroup relations. Both the potential problems and the potential benefits of bridging neuroscience and social psychology are considered in terms of theoretical considerations, empirical issues, and practical implications. We conclude that, although not all group phenomena may be reducible to neural activity and pathways, there are significant benefits to social psychology by having an even broader multidisciplinary orientation within social psychology, one that incorporates the complementary perspectives, techniques, and knowledge of neuroscience
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