scholarly journals The ASKAP/EMU Source Finding Data Challenge

2015 ◽  
Vol 32 ◽  
Author(s):  
A. M. Hopkins ◽  
M. T. Whiting ◽  
N. Seymour ◽  
K. E. Chow ◽  
R. P. Norris ◽  
...  
Keyword(s):  
Radio Source ◽  
Source Identification ◽  
The Other ◽  
Radio Continuum ◽  
Signal To Noise ◽  
Trade Off ◽  
Reliability And Robustness ◽  
Simulated Images ◽  
The Universe ◽  
Measurement Approach

AbstractThe Evolutionary Map of the Universe (EMU) is a proposed radio continuum survey of the Southern Hemisphere up to declination + 30°, with the Australian Square Kilometre Array Pathfinder (ASKAP). EMU will use an automated source identification and measurement approach that is demonstrably optimal, to maximise the reliability and robustness of the resulting radio source catalogues. As a step toward this goal we conducted a “Data Challenge” to test a variety of source finders on simulated images. The aim is to quantify the accuracy and limitations of existing automated source finding and measurement approaches. The Challenge initiators also tested the current ASKAPsoft source-finding tool to establish how it could benefit from incorporating successful features of the other tools. As expected, most finders show completeness around 100% at ≈ 10σ dropping to about 10% by ≈ 5σ. Reliability is typically close to 100% at ≈ 10σ, with performance to lower sensitivities varying between finders. All finders show the expected trade-off, where a high completeness at low signal-to-noise gives a corresponding reduction in reliability, and vice versa. We conclude with a series of recommendations for improving the performance of the ASKAPsoft source-finding tool.

scholarly journals Theoretical estimates of integrated Sachs–Wolfe effect detection through the Australian Square Kilometre Array Pathfinder’s Evolutionary Map of the Universe (ASKAP- EMU) survey, with confusion, position uncertainty, shot noise, and signal-to-noise ratio analysis

2015 ◽  
Vol 93 (4) ◽  
pp. 384-394 ◽  
Author(s):  
Syed Faisal ur Rahman
Keyword(s):  
Root Mean Square ◽  
Shot Noise ◽  
Radio Continuum ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Density Parameter ◽  
Mean Square ◽  
Signal To Noise ◽  
Position Uncertainty ◽  
Square Kilometre Array ◽  
The Universe

Detection of the late-time integrated Sachs–Wolfe (ISW) effect is an active area of study related to large-scale structures (LSSs). The ISW effect can be studied by observing the non-zero cross-correlation between cosmic microwave background (CMB) anisotropies with tracers of mass field, such as galaxy survey data. We study this effect by cross-correlating the CMB data and related cosmological parameters, as delineated by the Wilkinson Microwave Anisotropy Probe (WMAP), with the upcoming Evolutionary Map of the Universe (EMU) survey planned for the Australian Square Kilometre Array Pathfinder (ASKAP). ASKAP-EMU will conduct a deep radio continuum survey with a root-mean-square (rms) flux of 10 μJy per beam (1 Jy = 10–26 Wm–2Hz–1). The survey will cover the entire southern sky, extending to +30° declination. To infer the expected redshift distribution (dN/dz) and differential source count (S) that can be extracted from the galaxies surveyed via EMU, we use data from the S-cubed simulation of extragalactic radio continuum sources (S3-SEX) for the Square Kilometre Array Design Studies (SKADS). We also calculate various parameters including galaxy survey shot noise, root mean square confusion uncertainty, and position uncertainty for the survey, which can help in understanding the accuracy of the survey results and in performing the data analysis. We also discuss signal-to-noise ratios over a range of maximum redshifts and maximum multipole values with some discussion on constraints over dark energy density parameter (ΩΛ) and baryonic matter density parameter (Ωb).

scholarly journals An Improved Demodulation for LoRa Through a Threshold-Based Detection of Error

2021 ◽  
Author(s):  
Vincent Savaux
Keyword(s):  
Performance Analysis ◽  
Order Statistics ◽  
Error Rate ◽  
Detection Rate ◽  
The Other ◽  
Signal To Noise ◽  
Trade Off ◽  
Suggested Technique

This paper deals with an improved demodulation technique for LoRa signal. The principle consists in detecting the possible errors of demodulation, by comparing the highest peak of the periodogram of the dechirped received signal weighted by a coefficient beta? smaller than one with the other peaks of the periodogram. If an error is detected, a second demodulation stage is processed at an oversampling rate (OSR) higher than the first demodulation stage. Otherwise, the result of the first demodulation is kept. A thorough performance analysis of the suggested technique, based on order statistics, is carried out, in terms of detection rate, error rate, and complexity. It is shown that beta? can be tuned to adjusts the trade-off between performance and complexity. Moreover, simulations results shows that it is possible, for relatively low signal-to-noise (SNR) values, to reach the performance of the demodulation at highest OSR while keeping the complexity of the demodulation at lowest OSR.

scholarly journals An Improved Demodulation for LoRa Through a Threshold-Based Detection of Error

2021 ◽  
Author(s):  
Vincent Savaux
Keyword(s):  
Performance Analysis ◽  
Order Statistics ◽  
Error Rate ◽  
Detection Rate ◽  
The Other ◽  
Signal To Noise ◽  
Trade Off ◽  
Suggested Technique

This paper deals with an improved demodulation technique for LoRa signal. The principle consists in detecting the possible errors of demodulation, by comparing the highest peak of the periodogram of the dechirped received signal weighted by a coefficient beta? smaller than one with the other peaks of the periodogram. If an error is detected, a second demodulation stage is processed at an oversampling rate (OSR) higher than the first demodulation stage. Otherwise, the result of the first demodulation is kept. A thorough performance analysis of the suggested technique, based on order statistics, is carried out, in terms of detection rate, error rate, and complexity. It is shown that beta? can be tuned to adjusts the trade-off between performance and complexity. Moreover, simulations results shows that it is possible, for relatively low signal-to-noise (SNR) values, to reach the performance of the demodulation at highest OSR while keeping the complexity of the demodulation at lowest OSR.

scholarly journals The Large Scale Distribution of Radio Continuum in E and SO Galaxies

1978 ◽  
Vol 77 ◽  
pp. 49-55
Author(s):  
R.D. Ekers
Keyword(s):  
Radio Emission ◽  
Radio Source ◽  
Large Scale ◽  
Spiral Galaxies ◽  
Elliptical Galaxy ◽  
Elliptical Galaxies ◽  
The Other ◽  
Radio Continuum ◽  
Radio Structure ◽  
Similar Morphology

If we look at the radio properties of the nearby ellipticals we find a situation considerably different from that just described by van der Kruit for the spiral galaxies. For example NGC 5128 (Cen A), the nearest giant elliptical galaxy, is a thousand times more powerful a radio source than the brightest spiral galaxies and furthermore its radio emission comes from a multiple lobed radio structure which bears no resemblance to the optical light distribution (e.g. Ekers, 1975). The other radio emitting elliptical galaxies in our neighbourhood, NGC 1316 (Fornax A), IC 4296 (1333–33), have similar morphology. A question which then arises is whether at lower levels we can detect radio emission coming from the optical image of the elliptical galaxies and which may be more closely related to the kind of emission seen in the spiral galaxies.

scholarly journals An Improved Demodulation for LoRa Through a Threshold-Based Detection of Error

2021 ◽  
Author(s):  
Vincent Savaux
Keyword(s):  
Performance Analysis ◽  
Order Statistics ◽  
Error Rate ◽  
Detection Rate ◽  
The Other ◽  
Signal To Noise ◽  
Trade Off ◽  
Suggested Technique

This paper deals with an improved demodulation technique for LoRa signal. The principle consists in detecting the possible errors of demodulation, by comparing the highest peak of the periodogram of the dechirped received signal weighted by a coefficient beta? smaller than one with the other peaks of the periodogram. If an error is detected, a second demodulation stage is processed at an oversampling rate (OSR) higher than the first demodulation stage. Otherwise, the result of the first demodulation is kept. A thorough performance analysis of the suggested technique, based on order statistics, is carried out, in terms of detection rate, error rate, and complexity. It is shown that beta? can be tuned to adjusts the trade-off between performance and complexity. Moreover, simulations results shows that it is possible, for relatively low signal-to-noise (SNR) values, to reach the performance of the demodulation at highest OSR while keeping the complexity of the demodulation at lowest OSR.

scholarly journals Black Hole Algorithm for Sustainable Design of Counterfort Retaining Walls

2020 ◽  
Vol 12 (7) ◽  
pp. 2767 ◽  
Author(s):  
Víctor Yepes ◽  
José V. Martí ◽  
José García
Keyword(s):  
Black Hole ◽  
Sustainable Design ◽  
Retaining Walls ◽  
The Other ◽  
Trade Off ◽  
Construction Company ◽  
Geometric Variables ◽  
The Stability ◽  
The Cost ◽  
Black Hole Algorithm

The optimization of the cost and CO 2 emissions in earth-retaining walls is of relevance, since these structures are often used in civil engineering. The optimization of costs is essential for the competitiveness of the construction company, and the optimization of emissions is relevant in the environmental impact of construction. To address the optimization, black hole metaheuristics were used, along with a discretization mechanism based on min–max normalization. The stability of the algorithm was evaluated with respect to the solutions obtained; the steel and concrete values obtained in both optimizations were analyzed. Additionally, the geometric variables of the structure were compared. Finally, the results obtained were compared with another algorithm that solved the problem. The results show that there is a trade-off between the use of steel and concrete. The solutions that minimize CO 2 emissions prefer the use of concrete instead of those that optimize the cost. On the other hand, when comparing the geometric variables, it is seen that most remain similar in both optimizations except for the distance between buttresses. When comparing with another algorithm, the results show a good performance in optimization using the black hole algorithm.

scholarly journals Applying Ateb–Gabor Filters to Biometric Imaging Problems

Symmetry ◽  
2021 ◽  
Vol 13 (4) ◽  
pp. 717
Author(s):  
Mariia Nazarkevych ◽  
Natalia Kryvinska ◽  
Yaroslav Voznyi
Keyword(s):  
Wavelet Transformation ◽  
Symmetric Functions ◽  
Gabor Filter ◽  
Signal To Noise Ratio ◽  
The Other ◽  
Mean Square ◽  
Image Transformation ◽  
Gabor Filtering ◽  
Signal To Noise ◽  
Filtration Method

This article presents a new method of image filtering based on a new kind of image processing transformation, particularly the wavelet-Ateb–Gabor transformation, that is a wider basis for Gabor functions. Ateb functions are symmetric functions. The developed type of filtering makes it possible to perform image transformation and to obtain better biometric image recognition results than traditional filters allow. These results are possible due to the construction of various forms and sizes of the curves of the developed functions. Further, the wavelet transformation of Gabor filtering is investigated, and the time spent by the system on the operation is substantiated. The filtration is based on the images taken from NIST Special Database 302, that is publicly available. The reliability of the proposed method of wavelet-Ateb–Gabor filtering is proved by calculating and comparing the values of peak signal-to-noise ratio (PSNR) and mean square error (MSE) between two biometric images, one of which is filtered by the developed filtration method, and the other by the Gabor filter. The time characteristics of this filtering process are studied as well.

scholarly journals Investigating the properties of a galaxy group at z = 0.6

2020 ◽  
Vol 15 (S359) ◽  
pp. 188-189
Author(s):  
Daniela Hiromi Okido ◽  
Cristina Furlanetto ◽  
Marina Trevisan ◽  
Mônica Tergolina
Keyword(s):  
Large Scale ◽  
The Other ◽  
Numerical Density ◽  
Spectroscopy Data ◽  
Stellar Kinematics ◽  
Galaxy Groups ◽  
The Galaxy ◽  
The Difference ◽  
The Impact ◽  
The Universe

AbstractGalaxy groups offer an important perspective on how the large-scale structure of the Universe has formed and evolved, being great laboratories to study the impact of the environment on the evolution of galaxies. We aim to investigate the properties of a galaxy group that is gravitationally lensing HELMS18, a submillimeter galaxy at z = 2.39. We obtained multi-object spectroscopy data using Gemini-GMOS to investigate the stellar kinematics of the central galaxies, determine its members and obtain the mass, radius and the numerical density profile of this group. Our final goal is to build a complete description of this galaxy group. In this work we present an analysis of its two central galaxies: one is an active galaxy with z = 0.59852 ± 0.00007, while the other is a passive galaxy with z = 0.6027 ± 0.0002. Furthermore, the difference between the redshifts obtained using emission and absorption lines indicates an outflow of gas with velocity v = 278.0 ± 34.3 km/s relative to the galaxy.

Signature change in p-adic and noncommutative FRW cosmology

2014 ◽  
Vol 29 (27) ◽  
pp. 1450155 ◽  
Author(s):  
Goran S. Djordjevic ◽  
Ljubisa Nesic ◽  
Darko Radovancevic
Keyword(s):  
Loop Quantum Gravity ◽  
Initial Conditions ◽  
Planck Scale ◽  
The Other ◽  
Frw Cosmology ◽  
Signature Change ◽  
Discrete Nature ◽  
Frw Metric ◽  
The Universe ◽  
Friedmann Robertson Walker

The significant matter for the construction of the so-called no-boundary proposal is the assumption of signature transition, which has been a way to deal with the problem of initial conditions of the universe. On the other hand, results of Loop Quantum Gravity indicate that the signature change is related to the discrete nature of space at the Planck scale. Motivated by possibility of non-Archimedean and/or noncommutative structure of space–time at the Planck scale, in this work we consider the classical, p-adic and (spatial) noncommutative form of a cosmological model with Friedmann–Robertson–Walker (FRW) metric coupled with a self-interacting scalar field.

scholarly journals Geometric Approach to Analytic Marginalisation of the Likelihood Ratio for Continuous Gravitational Wave Searches

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 174
Author(s):  
Karl Wette
Keyword(s):  
Gravitational Wave ◽  
Likelihood Ratio ◽  
Signal To Noise Ratio ◽  
Geometric Approach ◽  
The Other ◽  
Efficient Computation ◽  
Likelihood Ratios ◽  
Signal To Noise ◽  
Noise Ratio ◽  
Optimal Signal

The likelihood ratio for a continuous gravitational wave signal is viewed geometrically as a function of the orientation of two vectors; one representing the optimal signal-to-noise ratio, and the other representing the maximised likelihood ratio or F-statistic. Analytic marginalisation over the angle between the vectors yields a marginalised likelihood ratio, which is a function of the F-statistic. Further analytic marginalisation over the optimal signal-to-noise ratio is explored using different choices of prior. Monte-Carlo simulations show that the marginalised likelihood ratios had identical detection power to the F-statistic. This approach demonstrates a route to viewing the F-statistic in a Bayesian context, while retaining the advantages of its efficient computation.

Sign in / Sign up

Export Citation Format

Share Document