51 research outputs found
Frequency Estimation Using Complex-Valued Shifted Window Transformer
Estimating closely spaced frequency components of a signal is a fundamental
problem in statistical signal processing. In this letter, we introduce 1-D
real-valued and complex-valued shifted window (Swin) transformers, referred to
as SwinFreq and CVSwinFreq, respectively, for line-spectra frequency estimation
on 1-D complex-valued signals. Whereas 2-D Swin transformer-based models have
gained traction for optical image super-resolution, we introduce for the first
time a complex-valued Swin module designed to leverage the complex-valued
nature of signals for a wide array of applications. The proposed approach
overcomes the limitations of the classical algorithms such as the periodogram,
MUSIC, and OMP in addition to state-of-the-art deep learning approach cResFreq.
SwinFreq and CVSwinFreq boast superior performance at low signal-to-noise ratio
SNR and improved resolution capability while requiring fewer model parameters
than cResFreq, thus deeming it more suitable for edge and mobile applications.
We find that the real-valued Swin-Freq outperforms its complex-valued
counterpart CVSwinFreq for several tasks while touting a smaller model size.
Finally, we apply the proposed techniques for radar range profile
super-resolution using real data. The results from both synthetic and real
experimentation validate the numerical and empirical superiority of SwinFreq
and CVSwinFreq to the state-of-the-art deep learning-based techniques and
traditional frequency estimation algorithms. The code and models are publicly
available at https://github.com/josiahwsmith10/spectral-super-resolution-swin.Comment: Submitted to IEEE Geoscience and Remote Sensing Letter
Emerging Approaches for THz Array Imaging: A Tutorial Review and Software Tool
Accelerated by the increasing attention drawn by 5G, 6G, and Internet of
Things applications, communication and sensing technologies have rapidly
evolved from millimeter-wave (mmWave) to terahertz (THz) in recent years.
Enabled by significant advancements in electromagnetic (EM) hardware, mmWave
and THz frequency regimes spanning 30 GHz to 300 GHz and 300 GHz to 3000 GHz,
respectively, can be employed for a host of applications. The main feature of
THz systems is high-bandwidth transmission, enabling ultra-high-resolution
imaging and high-throughput communications; however, challenges in both the
hardware and algorithmic arenas remain for the ubiquitous adoption of THz
technology. Spectra comprising mmWave and THz frequencies are well-suited for
synthetic aperture radar (SAR) imaging at sub-millimeter resolutions for a wide
spectrum of tasks like material characterization and nondestructive testing
(NDT). This article provides a tutorial review of systems and algorithms for
THz SAR in the near-field with an emphasis on emerging algorithms that combine
signal processing and machine learning techniques. As part of this study, an
overview of classical and data-driven THz SAR algorithms is provided, focusing
on object detection for security applications and SAR image super-resolution.
We also discuss relevant issues, challenges, and future research directions for
emerging algorithms and THz SAR, including standardization of system and
algorithm benchmarking, adoption of state-of-the-art deep learning techniques,
signal processing-optimized machine learning, and hybrid data-driven signal
processing algorithms...Comment: Submitted to Proceedings of IEE
Early-time spectroscopic modelling of the transitional Type Ia Supernova 2021rhu with TARDIS
An open question in SN Ia research is where the boundary lies between
'normal' Type Ia supernovae (SNe Ia) that are used in cosmological measurements
and those that sit off the Phillips relation. We present the spectroscopic
modelling of one such '86G-like' transitional SN Ia, SN 2021rhu, that has
recently been employed as a local Hubble Constant calibrator using a tip of the
red-giant branch measurement. We detail its modelling from -12 d until maximum
brightness using the radiative-transfer spectral-synthesis code tardis. We base
our modelling on literature delayed-detonation and deflagration models of
Chandrasekhar mass white dwarfs, as well as the double-detonation models of
sub-Chandrasekhar mass white dwarfs. We present a new method for 'projecting'
abundance profiles to different density profiles for ease of computation. Due
to the small velocity extent and low outer densities of the W7 profile, we find
it inadequate to reproduce the evolution of SN 2021rhu as it fails to match the
high-velocity calcium components. The host extinction of SN 2021rhu is
uncertain but we use modelling with and without an extinction correction to set
lower and upper limits on the abundances of individual species. Comparing these
limits to literature models we conclude that the spectral evolution of SN
2021rhu is also incompatible with double-detonation scenarios, lying more in
line with those resulting from the delayed detonation mechanism (although there
are some discrepancies, in particular a larger titanium abundance in SN 2021rhu
compared to the literature). This suggests that SN 2021rhu is likely a lower
luminosity, and hence lower temperature, version of a normal SN Ia.Comment: 25 pages, 22 figures, accepted for publication in MNRA
Self-love and sociability: the ‘rudiments of commerce’ in the state of nature
Istvan Hont’s classic work on the theoretical links between the seventeenth-century natural jurists Hugo Grotius and Samuel Pufendorf and the eighteenth-century Scottish political economists remains a popular trope among intellectual and economic historians of various stamps. Despite this, a common criticism levelled at Hont remains his relative lack of engagement with the relationship between religion and economics in the early modern period. This paper challenges this aspect of Hont’s narrative by drawing attention to an alternative, albeit complementary, assessment of the natural jurisprudential heritage of eighteenth-century British political economy. Specifically, the article attempts to map on to Hont’s thesis the Christian Stoic interpretation of Grotius and Pufendorf which has gained greater currency in recent years. In doing so, the paper argues that Grotius and Pufendorf’s contributions to the ‘unsocial sociability’ debate do not necessarily lead directly to the Scottish school of political economists, as is commonly assumed. Instead, it contends that a reconsideration of Grotius and Pufendorf as neo-Stoic theorists, particularly via scrutiny of their respective adaptations of the traditional Stoic theory of oikeiosis, steers us towards the heart of the early English ‘clerical’ Enlightenment
Three Hypervelocity White Dwarfs in Gaia DR2: Evidence for Dynamically Driven Double-Degenerate Double-Detonation Type Ia Supernovae
Double detonations in double white dwarf (WD) binaries undergoing unstable
mass transfer have emerged in recent years as one of the most promising Type Ia
supernova (SN Ia) progenitor scenarios. One potential outcome of this
"dynamically driven double-degenerate double-detonation" (D^6) scenario is that
the companion WD survives the explosion and is flung away with a velocity equal
to its > 1000 km/s pre-SN orbital velocity. We perform a search for these
hypervelocity runaway WDs using Gaia's second data release. In this paper, we
discuss seven candidates followed up with ground-based instruments. Three
sources are likely to be some of the fastest known stars in the Milky Way, with
total Galactocentric velocities between 1000 and 3000 km/s, and are consistent
with having previously been companion WDs in pre-SN Ia systems. However,
although the radial velocity of one of the stars is > 1000 km/s, the radial
velocities of the other two stars are puzzlingly consistent with 0. The
combined five-parameter astrometric solutions from Gaia and radial velocities
from follow-up spectra yield tentative 6D confirmation of the D^6 scenario. The
past position of one of these stars places it within a faint, old SN remnant,
further strengthening the interpretation of these candidates as hypervelocity
runaways from binary systems that underwent SNe Ia.Comment: Accepted for publication in ApJ. Minor corrections for clarity. D6
spectra are available as ancillary data file
Catching Element Formation In The Act
Gamma-ray astronomy explores the most energetic photons in nature to address
some of the most pressing puzzles in contemporary astrophysics. It encompasses
a wide range of objects and phenomena: stars, supernovae, novae, neutron stars,
stellar-mass black holes, nucleosynthesis, the interstellar medium, cosmic rays
and relativistic-particle acceleration, and the evolution of galaxies. MeV
gamma-rays provide a unique probe of nuclear processes in astronomy, directly
measuring radioactive decay, nuclear de-excitation, and positron annihilation.
The substantial information carried by gamma-ray photons allows us to see
deeper into these objects, the bulk of the power is often emitted at gamma-ray
energies, and radioactivity provides a natural physical clock that adds unique
information. New science will be driven by time-domain population studies at
gamma-ray energies. This science is enabled by next-generation gamma-ray
instruments with one to two orders of magnitude better sensitivity, larger sky
coverage, and faster cadence than all previous gamma-ray instruments. This
transformative capability permits: (a) the accurate identification of the
gamma-ray emitting objects and correlations with observations taken at other
wavelengths and with other messengers; (b) construction of new gamma-ray maps
of the Milky Way and other nearby galaxies where extended regions are
distinguished from point sources; and (c) considerable serendipitous science of
scarce events -- nearby neutron star mergers, for example. Advances in
technology push the performance of new gamma-ray instruments to address a wide
set of astrophysical questions.Comment: 14 pages including 3 figure
Jowett’s Thucydides: A corpus-based analysis of translation as political intervention
Thucydides’ History of the Peloponnesian War is a key text in the classical Greek canon and an important source of insights into the structures and tensions at the heart of ancient Athenian democracy. Consequently, modern interpretations of his analysis have repeatedly played a major role in shaping debates on the viability and desirability of democratic rule. This paper aims to build on previous discussion of Benjamin Jowett's 1881 translation of Thucydides by applying a comparative corpus-based methodology to explore how this translator's own personal politics shaped his re-presentation of this text. The analysis reveals a striking emphasis on the position and activity of democratic leaders throughout Jowett’s version, strongly consistent with the ideology of leadership that he developed during his career as Master of Balliol College, Oxford
Does diet affect breast cancer risk?
The role of specific dietary factors in breast cancer causation is not completely resolved. Results from prospective studies do not support the concept that fat intake in middle life has a major relation to breast cancer risk. However, weight gain in middle life contributes substantially to breast cancer risk. Alcohol is the best established dietary risk factor, probably by increasing endogenous estrogen levels. Hypotheses relating diet during youth to risk decades later will be difficult to test. Nevertheless, available evidence is strong that breast cancer risk can be reduced by avoiding weight gain during adult years, and by limiting alcohol consumption
LetsTalkShots: personalized vaccine risk communication
IntroductionVaccine hesitancy is a global health threat undermining control of many vaccine-preventable diseases. Patient-level education has largely been ineffective in reducing vaccine concerns and increasing vaccine uptake. We built and evaluated a personalized vaccine risk communication website called LetsTalkShots in English, Spanish and French (Canadian) for vaccines across the lifespan. LetsTalkShots tailors lived experiences, credible sources and informational animations to disseminate the right message from the right messenger to the right person, applying a broad range of behavioral theories.MethodsWe used mixed-methods research to test our animation and some aspects of credible sources and personal narratives. We conducted 67 discussion groups (n = 325 persons), stratified by race/ethnicity (African American, Hispanic, and White people) and population (e.g., parents, pregnant women, adolescents, younger adults, and older adults). Using a large Ipsos survey among English-speaking respondents (n = 2,272), we tested animations aligned with vaccine concerns and specific to population (e.g., parents of children, parents of adolescents, younger adults, older adults).ResultsDiscussion groups provided robust feedback specific to each animation as well as areas for improvements across animations. Most respondents indicated that the information presented was interesting (85.5%), clear (96.0%), helpful (87.0%), and trustworthy (82.2%).DiscussionTailored vaccine risk communication can assist decision makers as they consider vaccination for themselves, their families, and their communities. LetsTalkShots presents a model for personalized communication in other areas of medicine and public health
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