29,363 research outputs found
Data-driven Soft Sensors in the Process Industry
In the last two decades Soft Sensors established themselves as a valuable alternative to the traditional means for the acquisition of critical process variables, process monitoring and other tasks which are related to process control. This paper discusses characteristics of the process industry data which are critical for the development of data-driven Soft Sensors. These characteristics are common to a large number of process industry fields, like the chemical industry, bioprocess industry, steel industry, etc. The focus of this work is put on the data-driven Soft Sensors because of their growing popularity, already demonstrated usefulness and huge, though yet not completely realised, potential. A comprehensive selection of case studies covering the three most important Soft Sensor application fields, a general introduction to the most popular Soft Sensor modelling techniques as well as a discussion of some open issues in the Soft Sensor development and maintenance and their possible solutions are the main contributions of this work
First results from the IllustrisTNG simulations: radio haloes and magnetic fields
We introduce the IllustrisTNG project, a new suite of cosmological
magnetohydrodynamical simulations performed with the moving-mesh code AREPO
employing an updated Illustris galaxy formation model. Here we focus on the
general properties of magnetic fields and the diffuse radio emission in galaxy
clusters. Magnetic fields are prevalent in galaxies, and their build-up is
closely linked to structure formation. We find that structure formation
amplifies the initial seed fields ( comoving Gauss) to the values
observed in low-redshift galaxies (). The magnetic field
topology is closely connected to galaxy morphology such that irregular fields
are hosted by early-type galaxies, while large-scale, ordered fields are
present in disc galaxies. Using two simple models for the energy distribution
of relativistic electrons we predict the diffuse radio emission of
clusters with a baryonic mass resolution of , and generate mock observations for VLA, LOFAR, ASKAP and SKA. Our
simulated clusters show extended radio emission, whose detectability correlates
with their virial mass. We reproduce the observed scaling relations between
total radio power and X-ray emission, , and the Sunyaev-Zel'dovich
parameter. The radio emission surface brightness profiles of our
most massive clusters are in reasonable agreement with VLA measurements of Coma
and Perseus. Finally, we discuss the fraction of detected extended radio haloes
as a function of virial mass and source count functions for different
instruments. Overall our results agree encouragingly well with observations,
but a refined analysis requires a more sophisticated treatment of relativistic
particles in large-scale galaxy formation simulations.Comment: 28 pages, 18 figures, 2 tables, 3 appendices. Added a new
relativistic electron energy parametrization and text modifications to match
the accepted version for publication in MNRAS. More information, images and
movies of the IllustrisTNG project can be found at http://www.tng-project.or
A comprehensive asteroseismic modelling of the high-amplitude delta Scuti star RV Arietis
We present a comprehensive asteroseismic study of the double-mode
high-amplitude delta Scuti star HD 187642 (RV Arietis). The modelling includes
some of the most recent techniques: 1) effects of rotation on both equilibrium
models and adiabatic oscillation spectrum, 2) non-adiabatic study of radial and
non-radial modes, 3) relationship between the fundamental radial mode and the
first overtone in the framework of Petersen diagrams. The analysis reveals that
two of the observed frequencies are very probably identified as the fundamental
and first overtone radial modes. Analysis of the colour index variations,
together with theoretical non-adiabatic calculations, points to models in the
range of [7065,7245] K in effective temperature and of [1190, 1270] Myr in
stellar age. These values were found to be compatible with those obtained using
the three other asteroseismic techniques.Comment: accepted for publication in A&
On the dynamics of planetesimals embedded in turbulent protoplanetary discs
(abridged) Angular momentum transport and accretion in protoplanetary discs
are generally believed to be driven by MHD turbulence via the
magneto-rotational instability (MRI). The dynamics of solid bodies embedded in
such discs (dust grains, boulders, planetesimals and planets) may be strongly
affected by the turbulence, such that the formation pathways for planetary
systems are determined in part by the strength and spatial distribution of the
turbulent flow.
We examine the dynamics of planetesimals, with radii between 1m \^a 10 km,
embedded in turbulent protoplanetary discs, using three dimensional MHD
simulations. The planetesimals experience gas drag and stochastic gravitational
forces due to the turbulent disc. We use, and compare the results from, local
shearing box simulations and global models in this study.
The main aims of this work are to examine: the growth, and possible
saturation, of the velocity dispersion of embedded planetesimals as a function
of their size and disc parameters; the rate of radial migration and diffusion
of planetesimals; the conditions under which the results from shearing box and
global simulations agree.
We find good agreement between local and global simulations when shearing
boxes of dimension 4H x 16H x 2H are used (H being the local scale height). The
magnitude of the density fluctuations obtained is sensitive to the box size,
due to the excitation and propagation of spiral density waves. This affects the
stochastic forcing experienced by planetesimals. [...]
Our models show that fully developed MHD turbulence in protoplanetary discs
would have a destructive effect on embedded planetesimals. Relatively low
levels of turbulence are required for traditional models of planetesimal
accretion to operate, this being consistent with the existence of a dead zone
in protoplanetary discs.Comment: 23 pages, 28 figures, 3 tables, accepted for publication in MNRA
Ice condensation as a planet formation mechanism
We show that condensation is an efficient particle growth mechanism, leading
to growth beyond decimeter-sized pebbles close to an ice line in protoplanetary
discs. As coagulation of dust particles is frustrated by bouncing and
fragmentation, condensation could be a complementary, or even dominant, growth
mode in the early stages of planet formation. Ice particles diffuse across the
ice line and sublimate, and vapour diffusing back across the ice line
recondenses onto already existing particles, causing them to grow. We develop a
numerical model of the dynamical behaviour of ice particles close to the water
ice line, approximately 3 AU from the host star. Particles move with the
turbulent gas, modelled as a random walk. They also sediment towards the
midplane and drift radially towards the central star. Condensation and
sublimation are calculated using a Monte Carlo approach. Our results indicate
that, with a turbulent alpha-value of 0.01, growth from millimeter to at least
decimeter-sized pebbles is possible on a time scale of 1000 years. We find that
particle growth is dominated by ice and vapour transport across the radial ice
line, with growth due to transport across the atmospheric ice line being
negligible. Ice particles mix outwards by turbulent diffusion, leading to net
growth across the entire cold region. The resulting particles are large enough
to be sensitive to concentration by streaming instabilities, and in pressure
bumps and vortices, which can cause further growth into planetesimals. In our
model, particles are considered to be homogeneous ice particles. Taking into
account the more realistic composition of ice condensed onto rocky ice nuclei
might affect the growth time scales, by release of refractory ice nuclei after
sublimation. We also ignore sticking and fragmentation in particle collisions.
These effects will be the subject of future investigations.Comment: 15 pages, 11 figures. Accepted for publication in A&
Particle-based and Meshless Methods with Aboria
Aboria is a powerful and flexible C++ library for the implementation of
particle-based numerical methods. The particles in such methods can represent
actual particles (e.g. Molecular Dynamics) or abstract particles used to
discretise a continuous function over a domain (e.g. Radial Basis Functions).
Aboria provides a particle container, compatible with the Standard Template
Library, spatial search data structures, and a Domain Specific Language to
specify non-linear operators on the particle set. This paper gives an overview
of Aboria's design, an example of use, and a performance benchmark
Sub-Inertial Gravity Modes in the B8V Star KIC 7760680 Reveal Moderate Core Overshooting and Low Vertical Diffusive Mixing
KIC 7760680 is so far the richest slowly pulsating B star, by exhibiting 36
consecutive dipole () gravity (g-) modes. The monotonically decreasing
period spacing of the series, in addition to the local dips in the pattern
confirm that KIC 7760680 is a moderate rotator, with clear mode trapping in
chemically inhomogeneous layers. We employ the traditional approximation of
rotation to incorporate rotational effects on g-mode frequencies. Our detailed
forward asteroseismic modelling of this g-mode series reveals that KIC 7760680
is a moderately rotating B star with mass M. By
simultaneously matching the slope of the period spacing, and the number of
modes in the observed frequency range, we deduce that the equatorial rotation
frequency of KIC 7760680 is 0.4805 day, which is 26\% of its Roche break
up frequency. The relative deviation of the model frequencies and those
observed is less than one percent. We succeed to tightly constrain the
exponentially-decaying convective core overshooting parameter to . This means that convective core overshooting can
coexist with moderate rotation. Moreover, models with exponentially-decaying
overshoot from the core outperform those with the classical step-function
overshoot. The best value for extra diffusive mixing in the radiatively stable
envelope is confined to (with in cm sec), which is notably smaller than theoretical
predictions.Comment: 12 Figures, 2 Tables, all data publicly available for download;
accepted for publication in Astrophysical Journa
Stellar orbits in cosmological galaxy simulations: the connection to formation history and line-of-sight kinematics
We analyze orbits of stars and dark matter out to three effective radii for
42 galaxies formed in cosmological zoom simulations. Box orbits always dominate
at the centers and -tubes become important at larger radii. We connect the
orbital structure to the formation histories and specific features (e.g. disk,
counter-rotating core, minor axis rotation) in two-dimensional kinematic maps.
Globally, fast rotating galaxies with significant recent in situ star formation
are dominated by -tubes. Slow rotators with recent mergers have significant
box orbit and -tube components. Rotation, quantified by the
-parameter often originates from streaming motion of stars on
-tubes but sometimes from figure rotation. The observed anti-correlation of
and in rotating galaxies can be connected to a dissipative
formation history leading to high -tube fractions. For galaxies with recent
mergers in situ formed stars, accreted stars and dark matter particles populate
similar orbits. Dark matter particles have isotropic velocity dispersions.
Accreted stars are typically radially biased (). In
situ stars become tangentially biased (as low as ) if
dissipation was relevant during the late assembly of the galaxy. We discuss the
relevance of our analysis for integral field surveys and for constraining
galaxy formation models.Comment: 21 pages, 19 figure
Modelling of the fast rotating delta Scuti star Altair
We present an asteroseismic study of the fast rotating star HD187642
(Altair), recently discovered to be a delta Scuti pulsator. We have computed
models taking into account rotation for increasing rotational velocities. We
investigate the relation between the fundamental radial mode and the first
overtone in the framework of Petersen diagrams. The effects of rotation on such
diagrams, which become important at rotational velocities above 150 km/s, as
well as the domain of validity of our seismic tools are discussed. We also
investigate the radial and non-radial modes in order to constrain models
fitting the five most dominant observed oscillation modes.Comment: Accepted for publication in A&A (11 pages, 6 figures, 4 tables
- …