887,632 research outputs found
Analysis, Visualization, and Transformation of Audio Signals Using Dictionary-based Methods
date-added: 2014-01-07 09:15:58 +0000 date-modified: 2014-01-07 09:15:58 +0000date-added: 2014-01-07 09:15:58 +0000 date-modified: 2014-01-07 09:15:58 +000
Nonparametric estimation of the dynamic range of music signals
The dynamic range is an important parameter which measures the spread of
sound power, and for music signals it is a measure of recording quality. There
are various descriptive measures of sound power, none of which has strong
statistical foundations. We start from a nonparametric model for sound waves
where an additive stochastic term has the role to catch transient energy. This
component is recovered by a simple rate-optimal kernel estimator that requires
a single data-driven tuning. The distribution of its variance is approximated
by a consistent random subsampling method that is able to cope with the massive
size of the typical dataset. Based on the latter, we propose a statistic, and
an estimation method that is able to represent the dynamic range concept
consistently. The behavior of the statistic is assessed based on a large
numerical experiment where we simulate dynamic compression on a selection of
real music signals. Application of the method to real data also shows how the
proposed method can predict subjective experts' opinions about the hifi quality
of a recording
Water vapor and the dynamics of climate changes
Water vapor is not only Earth's dominant greenhouse gas. Through the release
of latent heat when it condenses, it also plays an active role in dynamic
processes that shape the global circulation of the atmosphere and thus climate.
Here we present an overview of how latent heat release affects atmosphere
dynamics in a broad range of climates, ranging from extremely cold to extremely
warm. Contrary to widely held beliefs, atmospheric circulation statistics can
change non-monotonically with global-mean surface temperature, in part because
of dynamic effects of water vapor. For example, the strengths of the tropical
Hadley circulation and of zonally asymmetric tropical circulations, as well as
the kinetic energy of extratropical baroclinic eddies, can be lower than they
presently are both in much warmer climates and in much colder climates. We
discuss how latent heat release is implicated in such circulation changes,
particularly through its effect on the atmospheric static stability, and we
illustrate the circulation changes through simulations with an idealized
general circulation model. This allows us to explore a continuum of climates,
constrain macroscopic laws governing this climatic continuum, and place past
and possible future climate changes in a broader context.Comment: 22 pages, 11 figure
Hydrological cycle in the Danube basin in present-day and XXII century simulations by IPCCAR4 global climate models
We present an intercomparison and verification analysis of 20 GCMs (Global
Circulation Models) included in the 4th IPCC assessment report regarding their
representation of the hydrological cycle on the Danube river basin for 1961–2000
and for the 2161–2200 SRESA1B scenario runs. The basin-scale properties of the
hydrological cycle are computed by spatially integrating the precipitation, evaporation,
and runoff fields using the Voronoi-Thiessen tessellation formalism. The span of the
model- simulated mean annual water balances is of the same order of magnitude of
the observed Danube discharge of the Delta; the true value is within the range
simulated by the models. Some land components seem to have deficiencies since there
are cases of violation of water conservation when annual means are considered. The
overall performance and the degree of agreement of the GCMs are comparable to those
of the RCMs (Regional Climate Models) analyzed in a previous work, in spite of the
much higher resolution and common nesting of the RCMs. The reanalyses are shown
to feature several inconsistencies and cannot be used as a verification benchmark for
the hydrological cycle in the Danubian region. In the scenario runs, for basically all
models the water balance decreases, whereas its interannual variability increases.
Changes in the strength of the hydrological cycle are not consistent among models:
it is confirmed that capturing the impact of climate change on the hydrological cycle
is not an easy task over land areas. Moreover, in several cases we find that qualitatively
different behaviors emerge among the models: the ensemble mean does not represent
any sort of average model, and often it falls between the models’ clusters
Cloud/climate sensitivity experiments
A study of the relationships between large-scale cloud fields and large scale circulation patterns is presented. The basic tool is a multi-level numerical model comprising conservation equations for temperature, water vapor and cloud water and appropriate parameterizations for evaporation, condensation, precipitation and radiative feedbacks. Incorporating an equation for cloud water in a large-scale model is somewhat novel and allows the formation and advection of clouds to be treated explicitly. The model is run on a two-dimensional, vertical-horizontal grid with constant winds. It is shown that cloud cover increases with decreased eddy vertical velocity, decreased horizontal advection, decreased atmospheric temperature, increased surface temperature, and decreased precipitation efficiency. The cloud field is found to be well correlated with the relative humidity field except at the highest levels. When radiative feedbacks are incorporated and the temperature increased by increasing CO2 content, cloud amounts decrease at upper-levels or equivalently cloud top height falls. This reduces the temperature response, especially at upper levels, compared with an experiment in which cloud cover is fixed
Corrugation of Roads
We present a one dimensional model for the development of corrugations in
roads subjected to compressive forces from a flux of cars. The cars are modeled
as damped harmonic oscillators translating with constant horizontal velocity
across the surface, and the road surface is subject to diffusive relaxation. We
derive dimensionless coupled equations of motion for the positions of the cars
and the road surface H(x,t), which contain two phenomenological variables: an
effective diffusion constant Delta(H) that characterizes the relaxation of the
road surface, and a function alpha(H) that characterizes the plasticity or
erodibility of the road bed. Linear stability analysis shows that corrugations
grow if the speed of the cars exceeds a critical value, which decreases if the
flux of cars is increased. Modifying the model to enforce the simple fact that
the normal force exerted by the road can never be negative seems to lead to
restabilized, quasi-steady road shapes, in which the corrugation amplitude and
phase velocity remain fixed.Comment: 20 pages, 8 figures, typos correcte
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