scholarly journals Constraining the reionization history using deep learning from 21-cm tomography with the Square Kilometre Array

2020 ◽  
Vol 494 (1) ◽  
pp. 600-606 ◽  
Author(s):  
Tumelo Mangena ◽  
Sultan Hassan ◽  
Mario G Santos
Keyword(s):  
High Redshift ◽  
Neutral Hydrogen ◽  
Power Spectral Analysis ◽  
High Accuracy ◽  
Neutral Fraction ◽  
Coefficient Of Determination ◽  
Data Sets ◽  
Imaging Data ◽  
Hydrogen Distribution ◽  
Power Spectral

ABSTRACT Upcoming 21-cm surveys with the SKA1-LOW telescope will enable imaging of the neutral hydrogen distribution on cosmological scales in the early Universe. These surveys are expected to generate huge imaging data sets that will encode more information than the power spectrum. This provides an alternative unique way to constrain the reionization history, which might break the degeneracy in the power spectral analysis. Using convolutional neural networks, we create a fast estimator of the neutral fraction from the 21-cm maps that are produced by our large seminumerical simulation. Our estimator is able to efficiently recover the neutral fraction ($x_{\rm H\,{\small I}}$) at several redshifts with a high accuracy of 99 per cent as quantified by the coefficient of determination R2. Adding the instrumental effects from the SKA design slightly increases the loss function, but nevertheless we are still able to recover the neutral fraction with a similar high accuracy of 98 per cent, which is only 1 per cent less. While a weak dependence on redshift is observed, the accuracy increases rapidly with decreasing neutral fraction. This is due to the fact that the instrumental noise increases towards high redshift where the Universe is highly neutral. Our results show the promise of directly using 21cm-tomography to constrain the reionization history in a model-independent way, complementing similar efforts, such as those of the optical depth measurements from the cosmic microwave background observations by Planck.

scholarly journals Galaxy formation and evolution using multi-wavelength, multi-resolution imaging data in the Virtual Observatory

2006 ◽  
Vol 2 (14) ◽  
pp. 592-592
Author(s):  
Paresh Prema ◽  
Nicholas A. Walton ◽  
Richard G. McMahon
Keyword(s):  
Galaxy Formation ◽  
High Redshift ◽  
Large Data ◽  
Electromagnetic Spectrum ◽  
Data Sets ◽  
Virtual Observatory ◽  
X Rays ◽  
Imaging Data ◽  
Wide Range ◽  
Multi Wavelength

Observational astronomy is entering an exciting new era with large surveys delivering deep multi-wavelength data over a wide range of the electromagnetic spectrum. The last ten years has seen a growth in the study of high redshift galaxies discovered with the method pioneered by Steidel et al. (1995) used to identify galaxies above z>1. The technique is designed to take advantage of the multi-wavelength data now available for astronomers that can extend from X-rays to radio wavelength. The technique is fast becoming a useful way to study large samples of objects at these high redshifts and we are currently designing and implementing an automated technique to study these samples of objects. However, large surveys produce large data sets that have now reached terabytes (e.g. for the Sloan Digital Sky Survey, <http://www.sdss.org>) in size and petabytes over the next 10yr (e.g., LSST, <http://www.lsst.org>). The Virtual Observatory is now providing a means to deal with this issue and users are now able to access many data sets in a quicker more useful form.

COMPARATIVE STUDY OF POWER SPECTRA OF GROUND AND SHALLOW UNDERGROUND MUON DATA

2005 ◽  
Vol 20 (29) ◽  
pp. 6953-6955 ◽  
Author(s):  
A. DRAGIĆ ◽  
R. BANJANAC ◽  
V. UDOVIČIĆ ◽  
D. JOKOVIĆ ◽  
I. ANIČIN ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Solar Rotation ◽  
Rotation Period ◽  
Power Spectra ◽  
Power Spectral Analysis ◽  
Ground Level ◽  
Data Sets ◽  
Power Spectral ◽  
Underground Detector ◽  
Scintillator Detectors

Cosmic muon flux is recorded by two plastic scintillator detectors: one located at ground level and the other located in the Belgrade underground laboratory (25 m w.e.). Power spectral analysis of the raw detector data for the period from January 1st 2002 to December 31st 2002 is performed. Similar periodicities are found in both data sets (ground and underground), but with different amplitudes. Main periodicity in the underground detector data has a 26.5 days period, while the highest amplitude signal in the ground detector data has a 243 ± 45 days period. Other signals present in the time series correspond to higher harmonics of the solar rotation period. There is also a wave with a 34.4 days period, whose significance is confirmed by different methods of spectral analysis. The same periodicity is recently found in some processes on the Sun.

scholarly journals Stacking redshifted 21 cm images of H ii regions around high-redshift galaxies as a probe of early reionization

2020 ◽  
Vol 501 (1) ◽  
pp. 146-156
Author(s):  
James E Davies ◽  
Rupert A C Croft ◽  
Tiziana Di-Matteo ◽  
Bradley Greig ◽  
Yu Feng ◽  
...  
Keyword(s):  
High Redshift ◽  
Neutral Hydrogen ◽  
Neutral Fraction ◽  
H Ii Regions ◽  
Fourier Space ◽  
Signal To Noise ◽  
First Stars ◽  
High Redshift Galaxies ◽  
H Ii Region ◽  
The Universe

ABSTRACT A number of current and future experiments aim to detect the reionization of neutral hydrogen by the first stars and galaxies in the Universe via the redshifted 21 cm line. Using the bluetides simulation, we investigate the measurement of an average ionized region towards the beginning of reionization by stacking redshifted 21 cm images around optically identified bright galaxies using mock observations. We find that with an SKA 1000 h observation, assuming perfect foreground subtraction, a 5σ detection of a stacked H ii region can be made with 30 images around some of the brightest galaxies in bluetides (brighter than MUV &lt; −22.75) at z = 9 (corresponding to a neutral fraction of 90.1 per cent in our model). We present simulated relationships between the UV magnitude of galaxies, the sizes of the ionized regions they reside in, and the shape of the stacked profiles. These mock observations can also distinguish between scenarios where the intergalactic medium is in net emission or absorption of 21 cm photons. Once 21 cm foreground contamination is included, we find that even with up to 200 images around these rare, bright galaxies, only a tentative &gt;1σ detection will be possible. However, partial foreground subtraction substantially improves signal to noise. For example, we predict that reducing the area of Fourier space dominated by foregrounds by 50 (80) per cent will allow &gt;3σ (&gt;5σ) detections of ionized regions at z = 9.

Inflections of Periodicities of Background Photon Spectral Power Densities Are Predicted by the Lorentz Contraction for a Potential Indicator for the Intrinsic Structure of Space

2016 ◽  
pp. 4014-4017
Author(s):  
Michael A Persinger
Keyword(s):  
Spectral Power ◽  
Neutral Hydrogen ◽  
Intrinsic Structure ◽  
Lorentz Contraction ◽  
Intrinsic Nature ◽  
Basic Interval ◽  
Power Spectral ◽  
The Difference ◽  
Background Photon ◽  
Power Densities

                The value for the Lorentz contraction to produce a discrepancy for a hypothetical number that reflects a property (21.3π4) of sub-matter space was calculated. When applied to time the contraction would be ~35 min. The difference in mass-equivalent energy for an electron at c (the velocity of light in a vacuum) and the required v was ~2 ·10-20 J which has emerged as a significant quantity that may permeate from the force at Planck’s Length when applied across the wavelength of the neutral hydrogen line. Two separate types of photomultiplier instruments (digital and analogue) measuring with different sampling rates for background photon quantities over 50 randomly selected days demonstrated averaged conspicuous inflections of standardized spectral power densities around 35 min. This is the same basic interval where microvariations in the value of the gravitational constant (G) approached a limit at which white noise dominated.  The possibility is considered that this value for temporal inflections in photon power spectral densities may reflect the intrinsic nature of space-time contractions that relate gravity and photons.

A computer vision approach to identifying the manufacturer and model of anterior cervical spinal hardware

2019 ◽  
Vol 31 (6) ◽  
pp. 844-850 ◽  
Author(s):  
Kevin T. Huang ◽  
Michael A. Silva ◽  
Alfred P. See ◽  
Kyle C. Wu ◽  
Troy Gallerani ◽  
...  
Keyword(s):  
Computer Vision ◽  
Feature Detection ◽  
High Accuracy ◽  
Detection Accuracy ◽  
Data Sets ◽  
Visual Words ◽  
Fusion Systems ◽  
Kaze Feature ◽  
Applications Of Machine Learning ◽  
Cervical Plating

OBJECTIVERecent advances in computer vision have revolutionized many aspects of society but have yet to find significant penetrance in neurosurgery. One proposed use for this technology is to aid in the identification of implanted spinal hardware. In revision operations, knowing the manufacturer and model of previously implanted fusion systems upfront can facilitate a faster and safer procedure, but this information is frequently unavailable or incomplete. The authors present one approach for the automated, high-accuracy classification of anterior cervical hardware fusion systems using computer vision.METHODSPatient records were searched for those who underwent anterior-posterior (AP) cervical radiography following anterior cervical discectomy and fusion (ACDF) at the authors’ institution over a 10-year period (2008–2018). These images were then cropped and windowed to include just the cervical plating system. Images were then labeled with the appropriate manufacturer and system according to the operative record. A computer vision classifier was then constructed using the bag-of-visual-words technique and KAZE feature detection. Accuracy and validity were tested using an 80%/20% training/testing pseudorandom split over 100 iterations.RESULTSA total of 321 total images were isolated containing 9 different ACDF systems from 5 different companies. The correct system was identified as the top choice in 91.5% ± 3.8% of the cases and one of the top 2 or 3 choices in 97.1% ± 2.0% and 98.4 ± 13% of the cases, respectively. Performance persisted despite the inclusion of variable sizes of hardware (i.e., 1-level, 2-level, and 3-level plates). Stratification by the size of hardware did not improve performance.CONCLUSIONSA computer vision algorithm was trained to classify at least 9 different types of anterior cervical fusion systems using relatively sparse data sets and was demonstrated to perform with high accuracy. This represents one of many potential clinical applications of machine learning and computer vision in neurosurgical practice.

Usefulness of Power Spectral Analysis for Measurement of Local Muscle Fatigue during Keyboard Task

1999 ◽  
Vol 11 (4) ◽  
pp. 449
Author(s):  
Soon Young Kwon ◽  
Chung Yill Park ◽  
Jung Wan Koo ◽  
Hyeon Woo Yim ◽  
Kang Sook Lee
Keyword(s):  
Spectral Analysis ◽  
Muscle Fatigue ◽  
Power Spectral Analysis ◽  
Power Spectral ◽  
Local Muscle Fatigue
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