14,101 research outputs found
Heat and work distributions for mixed Gauss-Cauchy process
We analyze energetics of a non-Gaussian process described by a stochastic
differential equation of the Langevin type. The process represents a
paradigmatic model of a nonequilibrium system subject to thermal fluctuations
and additional external noise, with both sources of perturbations considered as
additive and statistically independent forcings. We define thermodynamic
quantities for trajectories of the process and analyze contributions to
mechanical work and heat. As a working example we consider a particle subjected
to a drag force and two independent Levy white noises with stability indices
and . The fluctuations of dissipated energy (heat) and
distribution of work performed by the force acting on the system are addressed
by examining contributions of Cauchy fluctuations to either bath or external
force acting on the system
Transfer molding of PMR-15 polyimide resin
Transfer molding is an economically viable method of producing small shapes of PMR-15 polyimide. It is shown that with regard to flexural, compressive, and tribological properties transfer-molded PMR-15 polyimide is essentially equivalent to PMR-15 polyimide produced by the more common method of compression molding. Minor variations in anisotropy are predictable effects of molding design and secondary finishing operations
Invariant expectations and vanishing of bounded cohomology for exact groups
We study exactness of groups and establish a characterization of exact groups
in terms of the existence of a continuous linear operator, called an invariant
expectation, whose properties make it a weak counterpart of an invariant mean
on a group. We apply this operator to show that exactness of a finitely
generated group implies the vanishing of the bounded cohomology of with
coefficients in a new class of modules, which are defined using the Hopf
algebra structure of .Comment: Final version, to appear in the Journal of Topology and Analysi
Seeking for a fingerprint: analysis of point processes in actigraphy recording
Motor activity of humans displays complex temporal fluctuations which can be
characterized by scale-invariant statistics, thus documenting that structure
and fluctuations of such kinetics remain similar over a broad range of time
scales. Former studies on humans regularly deprived of sleep or suffering from
sleep disorders predicted change in the invariant scale parameters with respect
to those representative for healthy subjects. In this study we investigate the
signal patterns from actigraphy recordings by means of characteristic measures
of fractional point processes. We analyse spontaneous locomotor activity of
healthy individuals recorded during a week of regular sleep and a week of
chronic partial sleep deprivation. Behavioural symptoms of lack of sleep can be
evaluated by analysing statistics of duration times during active and resting
states, and alteration of behavioural organization can be assessed by analysis
of power laws detected in the event count distribution, distribution of waiting
times between consecutive movements and detrended fluctuation analysis of
recorded time series. We claim that among different measures characterizing
complexity of the actigraphy recordings and their variations implied by chronic
sleep distress, the exponents characterizing slopes of survival functions in
resting states are the most effective biomarkers distinguishing between healthy
and sleep-deprived groups.Comment: Communicated at UPON2015, 14-17 July 2015, Barcelona. 21 pages, 11
figures; updated: figures 4-7, text revised, expanded Sec. 1,3,
Radiative, actively cooled panel tests results
The radiative, actively cooled panel designed to withstand a uniform incident heat flux of 136 kW/sq m to a 444 K surface temperature was evaluated. The test program consisted of preliminary static thermal mechanical loading and aerothermal flow tests. Test results are briefly discussed
Study of 'ratio' automatically assembled structures final report, 15 jun. 1963 - 15 jun. 1964
Structural analysis of RATIO automatically assembled panel sections for application to spaceborne paraboloidal antenn
X-ray and Radio Monitoring of GX 339-4 and Cyg X-1
Previous work by Motch et al. (1985) suggested that in the low/hard state of
GX339-4, the soft X-ray power-law extrapolated backward in energy agrees with
the IR flux level. Corbel and Fender (2002) later showed that the typical hard
state radio power-law extrapolated forward in energy meets the backward
extrapolated X-ray power-law at an IR spectral break, which was explicitly
observed twice in GX339-4. This has been cited as further evidence that jet
synchrotron radiation might make a significant contribution to the observed
X-rays in the hard state. We explore this hypothesis with a series of
simultaneous radio/X-ray hard state observations of GX339-4. We fit these
spectra with a simple, but remarkably successful, doubly broken power-law model
that indeed requires a spectral break in the IR. For most of these
observations, the break position as a function of X-ray flux agrees with the
jet model predictions. We then examine the radio flux/X-ray flux correlation in
Cyg X-1 through the use of 15 GHz radio data, obtained with the Ryle radio
telescope, and Rossi X-ray Timing Explorer data, from the All Sky Monitor and
pointed observations. We find evidence of `parallel tracks' in the radio/X-ray
correlation which are associated with `failed transitions' to, or the beginning
of a transition to, the soft state. We also find that for Cyg X-1 the radio
flux is more fundamentally correlated with the hard, rather than the soft,
X-ray flux.Comment: To Appear in the Proceedings of "From X-ray Binaries to Quasars:
Black Hole Accretion on All Mass Scales" (Amsterdam, July 2004). Eds. T
Maccarone, R. Fender, L. H
Reasoning about transfinite sequences
We introduce a family of temporal logics to specify the behavior of systems
with Zeno behaviors. We extend linear-time temporal logic LTL to authorize
models admitting Zeno sequences of actions and quantitative temporal operators
indexed by ordinals replace the standard next-time and until future-time
operators. Our aim is to control such systems by designing controllers that
safely work on -sequences but interact synchronously with the system in
order to restrict their behaviors. We show that the satisfiability problem for
the logics working on -sequences is EXPSPACE-complete when the
integers are represented in binary, and PSPACE-complete with a unary
representation. To do so, we substantially extend standard results about LTL by
introducing a new class of succinct ordinal automata that can encode the
interaction between the different quantitative temporal operators.Comment: 38 page
A coarse grained model of granular compaction and relaxation
We introduce a theoretical model for the compaction of granular materials by discrete vibrations which is expected to hold when the intensity of vibration is low. The dynamical unit is taken to be clusters of granules that belong to the same collective structure. We rigourously construct the model from first principles and show that numerical solutions compare favourably with a range of experimental results. This includes the logarithmic relaxation towards a statistical steady state, the effect of varying the intensity of vibration resulting in a so-called `annealing' curve, and the power spectrum of density fluctuations in the steady state itself. A mean-field version of the model is introduced which shares many features with the exact model and is open to quantitative analysi
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