1,071 research outputs found
Neural modelling, control and optimisation of an industrial grinding process
This paper describes the development of neural model-based control strategies for the optimisation of an industrial aluminium
substrate disk grinding process. The grindstone removal rate varies considerably over a stone life and is a highly nonlinear function
of process variables. Using historical grindstone performance data, a NARX-based neural network model is developed. This model
is then used to implement a direct inverse controller and an internal model controller based on the process settings and previous
removal rates. Preliminary plant investigations show that thickness defects can be reduced by 50% or more, compared to other
schemes employed
Neural modelling, control and optimisation of an industrial grinding process
This paper describes the development of neural model-based control strategies for the optimisation of an industrial aluminium
substrate disk grinding process. The grindstone removal rate varies considerably over a stone life and is a highly nonlinear function
of process variables. Using historical grindstone performance data, a NARX-based neural network model is developed. This model
is then used to implement a direct inverse controller and an internal model controller based on the process settings and previous
removal rates. Preliminary plant investigations show that thickness defects can be reduced by 50% or more, compared to other
schemes employed
Tidal stirring and the origin of dwarf spheroidals in the Local Group
N-Body/SPH simulations are used to study the evolution of dwarf irregular
galaxies (dIrrs) entering the dark matter halo of the Milky Way or M31 on
plunging orbits. We propose a new dynamical mechanism driving the evolution of
gas rich, rotationally supported dIrrs, mostly found at the outskirts of the
Local Group (LG), into gas free, pressure supported dwarf spheroidals (dSphs)
or dwarf ellipticals (dEs), observed to cluster around the two giant spirals.
The initial model galaxies are exponential disks embedded in massive dark
matter halos and reproduce nearby dIrrs. Repeated tidal shocks at the
pericenter of their orbit partially strip their halo and disk and trigger
dynamical instabilities that dramatically reshape their stellar component.
After only 2-3 orbits low surface brightness (LSB) dIrrs are transformed into
dSphs, while high surface brightness (HSB) dIrrs evolve into dEs. This
evolutionary mechanism naturally leads to the morphology-density relation
observed for LG dwarfs. Dwarfs surrounded by very dense dark matter halos, like
the archetypical dIrr GR8, are turned into Draco or Ursa Minor, the faintest
and most dark matter dominated among LG dSphs. If disks include a gaseous
component, this is both tidally stripped and consumed in periodic bursts of
star formation. The resulting star formation histories are in good qualitative
agreement with those derived using HST color-magnitude diagrams for local
dSphs.Comment: 5 pages, 5 figures, to appear on ApJL. Simulation images and movies
can be found at the Local Group web page at
http://pcblu.uni.mi.astro.it/~lucio/LG/LG.htm
Recommended from our members
Individual Experience of Positive and Negative Growth is Asymmetric: Global Evidence from Subjective Well-being Data
Are individuals more sensitive to losses than gains in macroeconomic growth? Using subjective well-being measures across three large data sets, we observe an asymmetry in the way positive and negative economic growth are experienced, with losses having more than twice as much impact on individual happiness as compared to equivalent gains. We use Gallup World Poll data drawn from 151 countries, BRFSS data taken from a representative sample of 2.5 million US respondents, and Eurobarometer data that cover multiple business cycles over four decades. This research provides a new perspective on the welfare cost of business cycles with implications for growth pol- icy and our understanding of the long-run relationship between GDP and subjective well-being
Smooth HI Low Column Density Outskirts In Nearby Galaxies
This is an author-created, un-copyedited version of an article published in The Astronomical Journal. The Version of Record is available online at https://doi.org/10.3847/1538-3881/aabbaa.The low column density gas at the outskirts of galaxies as traced by the 21 cm hydrogen line emission (H i) represents the interface between galaxies and the intergalactic medium, i.e., where galaxies are believed to get their supply of gas to fuel future episodes of star formation. Photoionization models predict a break in the radial profiles of H i at a column density of ∼5 × 10 19 cm -2 due to the lack of self-shielding against extragalactic ionizing photons. To investigate the prevalence of such breaks in galactic disks and to characterize what determines the potential edge of the H i disks, we study the azimuthally averaged H i column density profiles of 17 nearby galaxies from the H i Nearby Galaxy Survey and supplemented in two cases with published Hydrogen Accretion in LOcal GAlaxieS data. To detect potential faint H i emission that would otherwise be undetected using conventional moment map analysis, we line up individual profiles to the same reference velocity and average them azimuthally to derive stacked radial profiles. To do so, we use model velocity fields created from a simple extrapolation of the rotation curves to align the profiles in velocity at radii beyond the extent probed with the sensitivity of traditional integrated H i maps. With this method, we improve our sensitivity to outer-disk H i emission by up to an order of magnitude. Except for a few disturbed galaxies, none show evidence of a sudden change in the slope of the H i radial profiles: the alleged signature of ionization by the extragalactic background.Peer reviewedFinal Accepted Versio
Probabilistic classification of acute myocardial infarction from multiple cardiac markers
Logistic regression and Gaussian mixture model (GMM) classifiers have been trained to estimate the probability of acute myocardial infarction (AMI) in patients based upon the concentrations of a panel of cardiac markers. The panel consists of two new markers, fatty acid binding protein (FABP) and glycogen phosphorylase BB (GPBB), in addition to the traditional cardiac troponin I (cTnI), creatine kinase MB (CKMB) and myoglobin. The effect of using principal component analysis (PCA) and Fisher discriminant analysis (FDA) to preprocess the marker concentrations was also investigated. The need for classifiers to give an accurate estimate of the probability of AMI is argued and three categories of performance measure are described, namely discriminatory ability, sharpness, and reliability. Numerical performance measures for each category are given and applied. The optimum classifier, based solely upon the samples take on admission, was the logistic regression classifier using FDA preprocessing. This gave an accuracy of 0.85 (95% confidence interval: 0.78–0.91) and a normalised Brier score of 0.89. When samples at both admission and a further time, 1–6 h later, were included, the performance increased significantly, showing that logistic regression classifiers can indeed use the information from the five cardiac markers to accurately and reliably estimate the probability AMI
CHANG-ES VI: Probing Supernova Energy Deposition in Spiral Galaxies Through Multi-Wavelength Relationships
How a galaxy regulates its SNe energy into different
interstellar/circumgalactic medium components strongly affects galaxy
evolution. Based on the JVLA D-configuration C- (6 GHz) and L-band (1.6 GHz)
continuum observations, we perform statistical analysis comparing
multi-wavelength properties of the CHANG-ES galaxies. The high-quality JVLA
data and edge-on orientation enable us for the first time to include the halo
into the energy budget for a complete radio-flux-limited sample. We find tight
correlations of with the mid-IR-based SFR. The normalization of
our relation is 2-3 times of
those obtained for face-on galaxies, probably a result of enhanced IR
extinction at high inclination. We also find tight correlations between and the SNe energy injection rate , indicating
the energy loss via synchrotron radio continuum accounts for of
, comparable to the energy contained in CR electrons. The
integrated C-to-L-band spectral index is for non-AGN
galaxies, indicating a dominance by the diffuse synchrotron component. The
low-scatter /
relationships have super-linear logarithmic slopes at in L-band
(/) while consistent with linear in C-band
(/). The super-linearity could be naturally
reproduced with non-calorimeter models for galaxy disks. Using Chandra halo
X-ray measurements, we find sub-linear relations.
These results indicate that the observed radio halo of a starburst galaxy is
close to electron calorimeter, and a galaxy with higher SFR tends to distribute
an increased fraction of SNe energy into radio emission (than X-ray).Comment: 16 pages, 6 figures, 1 table, MNRAS in pres
CHANG-ES IV: Radio continuum emission of 35 edge-on galaxies observed with the Karl G. Jansky Very Large Array in D-configuration, Data Release 1
We present the first part of the observations made for the Continuum Halos in
Nearby Galaxies, an EVLA Survey (CHANG-ES) project. The aim of the CHANG-ES
project is to study and characterize the nature of radio halos, their
prevalence as well as their magnetic fields, and the cosmic rays illuminating
these fields. This paper reports observations with the compact D configuration
of the Karl G. Jansky Very Large Array (VLA) for the sample of 35 nearby
edge-on galaxies of CHANG-ES. With the new wide bandwidth capabilities of the
VLA, an unprecedented sensitivity was achieved for all polarization products.
The beam resolution is an average of 9.6" and 36" with noise levels reaching
approximately 6 and 30 microJy per beam for C- and L-bands, respectively
(robust weighting). We present intensity maps in these two frequency bands (C
and L), with different weightings, as well as spectral index maps, polarization
maps, and new measurements of star formation rates (SFRs). The data products
described herein are available to the public in the CHANG-ES data release
available at www.queensu.ca/changes. We also present evidence of a trend among
galaxies with larger halos having higher SFR surface density, and we show, for
the first time, a radio continuum image of the median galaxy, taking advantage
of the collective signal-to-noise ratio of 30 of our galaxies. This image shows
clearly that a typical spiral galaxy is surrounded by a halo of magnetic fields
and cosmic rays.Comment: 70 pages, of which 35 pages present the data of each galax
- …