11,903 research outputs found
Surface electrical properties experiment, part 1
The work is reported which was performed on the Surface Electrical Properties Experiment Data Acquisition System. Areas discussed include: data handling and processing, installation and external signal application, operation of the equipment, and digital output. Detailed circuit descriptions are included
Spatial coherence resonance on diffusive and small-world networks of Hodgkin-Huxley neurons
Spatial coherence resonance in a spatially extended system that is locally
modeled by Hodgkin-Huxley (HH) neurons is studied in this paper. We focus on
the ability of additive temporally and spatially uncorrelated Gaussian noise to
extract a particular spatial frequency of excitatory waves in the medium,
whereby examining also the impact of diffusive and small-world network topology
determining the interactions amongst coupled HH neurons. We show that there
exists an intermediate noise intensity that is able to extract a characteristic
spatial frequency of the system in a resonant manner provided the latter is
diffusively coupled, thus indicating the existence of spatial coherence
resonance. However, as the diffusive topology of the medium is relaxed via the
introduction of shortcut links introducing small-world properties amongst
coupled HH neurons, the ability of additive Gaussian noise to evoke ordered
excitatory waves deteriorates rather spectacularly, leading to the decoherence
of the spatial dynamics and with it related absence of spatial coherence
resonance. In particular, already a minute fraction of shortcut links suffices
to substantially disrupt coherent pattern formation in the examined system.Comment: 8 two-column pages, 6 figures; accepted for publication in Chao
Evaluation of be-38 percent al alloy final report, 27 jun. 1964 - 28 feb. 1965
Mechanical properties, microstructural features, and general metallurgical quality of beryllium- aluminum allo
Non-nequilibrium model on Apollonian networks
We investigate the Majority-Vote Model with two states () and a noise
on Apollonian networks. The main result found here is the presence of the
phase transition as a function of the noise parameter . We also studies de
effect of redirecting a fraction of the links of the network. By means of
Monte Carlo simulations, we obtained the exponent ratio ,
, and for several values of rewiring probability . The
critical noise was determined and also was calculated. The
effective dimensionality of the system was observed to be independent on ,
and the value is observed for these networks. Previous
results on the Ising model in Apollonian Networks have reported no presence of
a phase transition. Therefore, the results present here demonstrate that the
Majority-Vote Model belongs to a different universality class as the
equilibrium Ising Model on Apollonian Network.Comment: 5 pages, 5 figure
Evidence from satellite altimetry for small-scale convection in the mantle
Small scale convection can be defined as that part of the mantle circulation in which upwellings and downwellings can occur beneath the lithosphere within the interiors of plates, in contrast to the large scale flow associated with plate motions where upwellings and downwellings occur at ridges and trenches. The two scales of convection will interact so that the form of the small scale convection will depend on how it arises within the large scale flow. Observations based on GEOS-3 and SEASAT altimetry suggest that small scale convection occurs in at least two different ways
STEPS - an approach for human mobility modeling
In this paper we introduce Spatio-TEmporal Parametric Stepping (STEPS) - a simple parametric mobility model which can cover a large spectrum of human mobility patterns. STEPS makes abstraction of spatio-temporal preferences in human mobility by using a power law to rule the nodes movement. Nodes in STEPS have preferential attachment to favorite locations where they spend most of their time. Via simulations, we show that STEPS is able, not only to express the peer to peer properties such as inter-ontact/contact time and to reflect accurately realistic routing performance, but also to express the structural properties of the underlying interaction graph such as small-world phenomenon. Moreover, STEPS is easy to implement, exible to configure and also theoretically tractable
Enhancing complex-network synchronization
Heterogeneity in the degree (connectivity) distribution has been shown to
suppress synchronization in networks of symmetrically coupled oscillators with
uniform coupling strength (unweighted coupling). Here we uncover a condition
for enhanced synchronization in directed networks with weighted coupling. We
show that, in the optimum regime, synchronizability is solely determined by the
average degree and does not depend on the system size and the details of the
degree distribution. In scale-free networks, where the average degree may
increase with heterogeneity, synchronizability is drastically enhanced and may
become positively correlated with heterogeneity, while the overall cost
involved in the network coupling is significantly reduced as compared to the
case of unweighted coupling.Comment: 4 pages, 3 figure
Recovery of Large Angular Scale CMB Polarization for Instruments Employing Variable-delay Polarization Modulators
Variable-delay Polarization Modulators (VPMs) are currently being implemented
in experiments designed to measure the polarization of the cosmic microwave
background on large angular scales because of their capability for providing
rapid, front-end polarization modulation and control over systematic errors.
Despite the advantages provided by the VPM, it is important to identify and
mitigate any time-varying effects that leak into the synchronously modulated
component of the signal. In this paper, the effect of emission from a K
VPM on the system performance is considered and addressed. Though instrument
design can greatly reduce the influence of modulated VPM emission, some
residual modulated signal is expected. VPM emission is treated in the presence
of rotational misalignments and temperature variation. Simulations of
time-ordered data are used to evaluate the effect of these residual errors on
the power spectrum. The analysis and modeling in this paper guides
experimentalists on the critical aspects of observations using VPMs as
front-end modulators. By implementing the characterizations and controls as
described, front-end VPM modulation can be very powerful for mitigating
noise in large angular scale polarimetric surveys. None of the systematic
errors studied fundamentally limit the detection and characterization of
B-modes on large scales for a tensor-to-scalar ratio of . Indeed,
is achievable with commensurately improved characterizations and
controls.Comment: 13 pages, 13 figures, 1 table, matches published versio
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