208 research outputs found
Interpolating Masked Weak Lensing Signal with Karhunen-Loeve Analysis
We explore the utility of Karhunen Loeve (KL) analysis in solving practical
problems in the analysis of gravitational shear surveys. Shear catalogs from
large-field weak lensing surveys will be subject to many systematic
limitations, notably incomplete coverage and pixel-level masking due to
foreground sources. We develop a method to use two dimensional KL eigenmodes of
shear to interpolate noisy shear measurements across masked regions. We explore
the results of this method with simulated shear catalogs, using statistics of
high-convergence regions in the resulting map. We find that the KL procedure
not only minimizes the bias due to masked regions in the field, it also reduces
spurious peak counts from shape noise by a factor of ~ 3 in the cosmologically
sensitive regime. This indicates that KL reconstructions of masked shear are
not only useful for creating robust convergence maps from masked shear
catalogs, but also offer promise of improved parameter constraints within
studies of shear peak statistics.Comment: 13 pages, 9 figures; submitted to Ap
3D Reconstruction of the Density Field: An SVD Approach to Weak Lensing Tomography
We present a new method for constructing three-dimensional mass maps from
gravitational lensing shear data. We solve the lensing inversion problem using
truncation of singular values (within the context of generalized least squares
estimation) without a priori assumptions about the statistical nature of the
signal. This singular value framework allows a quantitative comparison between
different filtering methods: we evaluate our method beside the previously
explored Wiener filter approaches. Our method yields near-optimal angular
resolution of the lensing reconstruction and allows cluster sized halos to be
de-blended robustly. It allows for mass reconstructions which are 2-3
orders-of-magnitude faster than the Wiener filter approach; in particular, we
estimate that an all-sky reconstruction with arcminute resolution could be
performed on a time-scale of hours. We find however that linear, non-parametric
reconstructions have a fundamental limitation in the resolution achieved in the
redshift direction.Comment: 11 pages, 6 figures. Accepted for publication in Ap
Using Open Source Libraries in the Development of Control Systems Based on Machine Vision
The possibility of the boundaries detection in the images of crushed ore particles using a convolutional neural network is analyzed. The structure of the neural network is given. The construction of training and test datasets of ore particle images is described. Various modifications of the underlying neural network have been investigated. Experimental results are presented. © 2020, IFIP International Federation for Information Processing.Foundation for Assistance to Small Innovative Enterprises in Science and Technology, FASIEFunding. The work was performed under state contract 3170ΓC1/48564, grant from the FASIE
Improving SIEM for critical SCADA water infrastructures using machine learning
Network Control Systems (NAC) have been used in many industrial processes. They aim to reduce the human factor burden and efficiently handle the complex process and communication of those systems. Supervisory control and data acquisition (SCADA) systems are used in industrial, infrastructure and facility processes (e.g. manufacturing, fabrication, oil and water pipelines, building ventilation, etc.) Like other Internet of Things (IoT) implementations, SCADA systems are vulnerable to cyber-attacks, therefore, a robust anomaly detection is a major requirement. However, having an accurate anomaly detection system is not an easy task, due to the difficulty to differentiate between cyber-attacks and system internal failures (e.g. hardware failures). In this paper, we present a model that detects anomaly events in a water system controlled by SCADA. Six Machine Learning techniques have been used in building and evaluating the model. The model classifies different anomaly events including hardware failures (e.g. sensor failures), sabotage and cyber-attacks (e.g. DoS and Spoofing). Unlike other detection systems, our proposed work helps in accelerating the mitigation process by notifying the operator with additional information when an anomaly occurs. This additional information includes the probability and confidence level of event(s) occurring. The model is trained and tested using a real-world dataset
Machine learning based IoT Intrusion Detection System:an MQTT case study (MQTT-IoT-IDS2020 Dataset)
The Internet of Things (IoT) is one of the main research fields in the Cybersecurity domain. This is due to (a) the increased dependency on automated device, and (b) the inadequacy of general-purpose Intrusion Detection Systems (IDS) to be deployed for special purpose networks usage. Numerous lightweight protocols are being proposed for IoT devices communication usage. One of the distinguishable IoT machine-to-machine communication protocols is Message Queuing Telemetry Transport (MQTT) protocol. However, as per the authors best knowledge, there are no available IDS datasets that include MQTT benign or attack instances and thus, no IDS experimental results available. In this paper, the effectiveness of six Machine Learning (ML) techniques to detect MQTT-based attacks is evaluated. Three abstraction levels of features are assessed, namely, packet-based, unidirectional flow, and bidirectional flow features. An MQTT simulated dataset is generated and used for the training and evaluation processes. The dataset is released with an open access licence to help the research community further analyse the accompanied challenges. The experimental results demonstrated the adequacy of the proposed ML models to suit MQTT-based networks IDS requirements. Moreover, the results emphasise on the importance of using flow-based features to discriminate MQTT-based attacks from benign traffic, while packet-based features are sufficient for traditional networking attacks
First-Year Sloan Digital Sky Survey-II (SDSS-II) Supernova Results: Constraints on Non-Standard Cosmological Models
We use the new SNe Ia discovered by the SDSS-II Supernova Survey together
with additional supernova datasets as well as observations of the cosmic
microwave background and baryon acoustic oscillations to constrain cosmological
models. This complements the analysis presented by Kessler et al. in that we
discuss and rank a number of the most popular non-standard cosmology scenarios.
When this combined data-set is analyzed using the MLCS2k2 light-curve fitter,
we find that more exotic models for cosmic acceleration provide a better fit to
the data than the Lambda-CDM model. For example, the flat DGP model is ranked
higher by our information criteria tests than the standard model. When the
dataset is instead analyzed using the SALT-II light-curve fitter, the standard
cosmological constant model fares best. Our investigation also includes
inhomogeneous Lemaitre-Tolman-Bondi (LTB) models. While our LTB models can be
made to fit the supernova data as well as any other model, the extra parameters
they require are not supported by our information criteria analysis.Comment: ApJ in press, updated reference
A Compressed Sensing Approach to 3D Weak Lensing
(Abridged) Weak gravitational lensing is an ideal probe of the dark universe.
In recent years, several linear methods have been developed to reconstruct the
density distribution in the Universe in three dimensions, making use of
photometric redshift information to determine the radial distribution of lensed
sources. In this paper, we aim to address three key issues seen in these
methods; namely, the bias in the redshifts of detected objects, the line of
sight smearing seen in reconstructions, and the damping of the amplitude of the
reconstruction relative to the underlying density. We consider the problem
under the framework of compressed sensing (CS). Under the assumption that the
data are sparse in an appropriate dictionary, we construct a robust estimator
and employ state-of-the-art convex optimisation methods to reconstruct the
density contrast. For simplicity in implementation, and as a proof of concept
of our method, we reduce the problem to one-dimension, considering the
reconstruction along each line of sight independently. Despite the loss of
information this implies, we demonstrate that our method is able to accurately
reproduce cluster haloes up to a redshift of z=1, deeper than state-of-the-art
linear methods. We directly compare our method with these linear methods, and
demonstrate minimal radial smearing and redshift bias in our reconstructions,
as well as a reduced damping of the reconstruction amplitude as compared to the
linear methods. In addition, the CS framework allows us to consider an
underdetermined inverse problem, thereby allowing us to reconstruct the density
contrast at finer resolution than the input data.Comment: Submitted to A&A (6 July 2011
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