167 research outputs found
Dataset for Mapping Stellar Surfaces II: An interpretable Gaussian process model for light curves
No full textDataset used in the generation of the figures in Luger et al. (2021)
Dataset for Mapping Stellar Surfaces I: Degeneracies in the rotational light curve problem
No full textDataset used in the generation of the figures in Luger et al. (2021)
Simulated gunshot with: (A) .40-caliber S&W bullet; (B) 9×19-mm Luger bullet; (C) .380-caliber bullet.
No full text<p>Simulated gunshot with: (A) .40-caliber S&W bullet; (B) 9×19-mm Luger bullet; (C) .380-caliber bullet.</p
von Mises stress distribution and wounds in both orbital roofs of the skull model after each shooting simulation (A) FMJ FP.40 S (B) FMJ RN 9×19-mm Luger; (C) FMJ RN.380.
No full text<p>von Mises stress distribution and wounds in both orbital roofs of the skull model after each shooting simulation (A) FMJ FP.40 S (B) FMJ RN 9×19-mm Luger; (C) FMJ RN.380.</p
Comparison of gunshot entrance morphologies caused by .40-caliber Smith & Wesson, .380-caliber, and 9-mm Luger bullets: a finite element analysis study.
No full textFirearms can cause fatal wounds, which can be identified by traces on or around the body. However, there are cases where neither the bullet nor gun is found at the crime scene. Ballistic research involving finite element models can reproduce computational biomechanical conditions, without compromising bioethics, as they involve no direct tests on animals or humans. This study aims to compare the morphologies of gunshot entrance holes caused by.40-caliber Smith & Wesson (S&W), .380-caliber, and 9×19-mm Luger bullets. A fully metal-jacketed.40 S&W projectile, a fully metal-jacketed.380 projectile, and a fully metal-jacketed 9×19-mm Luger projectile were computationally fired at the glabellar region of the finite element model from a distance of 10 cm, at perpendicular incidence. The results show different morphologies in the entrance holes produced by the three bullets, using the same skull at the same shot distance. The results and traits of the entrance holes are discussed. Finite element models allow feasible computational ballistic research, which may be useful to forensic experts when comparing and analyzing data related to gunshot wounds in the forehead
EVEREST
No full text<p><strong>EVEREST</strong> (EPIC Variability Extraction and Removal for Exoplanet Science Targets) is an open-source pipeline for removing instrumental noise from light curves generated by <em>K2</em>, the repurposed <em>Kepler</em> spacecraft. Operating with only two of four reaction wheels, <em>K2</em> is unable to maintain the precise pointing precision required to detect the small light modulations caused by transiting exoplanets. <strong>EVEREST</strong> exploits correlations across the pixels on the <em>Kepler</em> CCD to remove systematics introduced by the spacecraft's pointing error, yielding light curves with precision comparable to that of the original<em>Kepler</em> mission.</p>
Vallende ankers op tunneldaken
No full textIn opdracht van de Bouwdienst Rijkswaterstaat Utrecht is door Grondmecbanica Delft onderzoek gedaan naar het indringsmechanisme vaneen vallend anker in een afdekkende laag op een tunneldak. Dit rapport geeft de resultaten van de vijfde fase van het VALANK project Weer. In deze fase van het onderzoek is gebruik gemaakt vaneen zgn. dipoolmodel. Dit analytische model is uitgewerkt in een Pascal programma De resultaten van de analyses die hiermee zijn uitgevoerd zijn vertaald naar ontwerpgrafieken. De ontwerpgrafieken geven voor verschillende ankermassa' s, valsnelheden en diktes van de afdeklaag de resulterende maximale kracht, de einddiepte waar het anker stopt en in het geval van raken de eindsnelheid van het anker.Valan
Joint Modeling of Radial Velocities and Photometry with a Gaussian Process Framework
No full textDevelopments in the stability of modern spectrographs have led to extremely
precise instrumental radial velocity (RV) measurements. For most stars, the
detection limit of planetary companions with these instruments is expected to
be dominated by astrophysical noise sources such as starspots. Correlated
signals caused by rotationally-modulated starspots can obscure or mimic the
Doppler shifts induced by even the closest, most massive planets. This is
especially true for young, magnetically active stars where stellar activity can
cause fluctuation amplitudes of 0.1 mag in brightness and 100
m s in RV semi-amplitudes. Techniques that can mitigate these effects
and increase our sensitivity to young planets are critical to improving our
understanding of the evolution of planetary systems. Gaussian processes (GPs)
have been successfully employed to model and constrain activity signals in
individual cases. However, a principled approach of this technique,
specifically for the joint modeling of photometry and RVs, has not yet been
developed. In this work, we present a GP framework to simultaneously model
stellar activity signals in photometry and RVs that can be used to investigate
the relationship between both time series. Our method, inspired by the
framework of (Aigrain et al. 2012), models spot-driven
activity signals as the linear combinations of two independent latent GPs and
their time derivatives. We also simulate time series affected by starspots by
extending the software (Luger et al. 2019) to incorporate
time evolution of stellar features. Using these synthetic datasets, we show
that our method can predict spot-driven RV variations with greater accuracy
than other GP approaches.Comment: 19 pages, 10 figure
On The Evolution, Detection, and Characterization of Small Planets in the Habitable Zones of M Dwarfs
No full textThesis (Ph.D.)--University of Washington, 2017-08As the technology behind instrumentation in astronomy improves, so too does our ability to detect and characterize worlds outside our solar system. We are currently witnessing a revolution in exoplanet science: for the past three decades, the number of known planets orbiting other stars has grown exponentially, showing no signs of tapering off. We now know of dozens of small planets in the habitable zones of their stars, and this number is expected to grow with upcoming survey missions such as the Transiting Exoplanet Survey Satellite (TESS) and the PLAnetary Transits and Oscillations telescope (PLATO). Improving commensurately with our capacity to detect these planets is our ability to characterize them. Missions such as the James Webb Space Telescope (JWST) and subsequent generations of space-based telescopes will be capable of characterizing these planets' atmospheres and searching for molecular signatures of habitability and life. Given the large number of potentially habitable planets we will soon discover, knowing which targets to prioritize for follow-up observations is paramount to furthering our goal of understanding the potential for habitability of exoplanets. Once data becomes available, its interpretation will rely heavily on a physical understanding of the processes that contribute to making a planet habitable (or not). Models of the evolutionary processes of potentially habitable planets can therefore improve target selection for biosignature searches and enhance the science return from terrestrial planet characterization. In this dissertation, I develop theoretical models of the evolution of the atmospheres and surface water inventories of planets in the habitable zones of low mass stars. While these stars currently offer the best opportunity to characterize potentially habitable planets, my work shows that vigorous atmospheric escape from these planets due to intense stellar activity could render many of them uninhabitable. I discuss observational signatures of the escape process and best case scenarios for planets around low mass stars, including the possibility that planets that form with substantial primordial atmospheres of hydrogen and helium could weather the active phase of the host star without substantial devolatilization. I also refine existing techniques to detect and characterize exoplanets, with particular emphasis on small planets in the habitable zones of low mass stars. I introduce EVEREST, a pipeline to remove instrumental noise from photometric datasets and enable the detection of planet transit signals that would otherwise be hidden in the noise. Furthermore, I develop two novel techniques for the detection and characterization of potentially habitable exoplanets: the exo-auroral method, which relies on the spectroscopic detection of auroral emission from terrestrial planets, and planet-planet occultations, wherein an exoplanet occults another planet in the same system, imparting a small photometric signal on the system's light curve. I show how the next generation of telescopes may enable the application of both techniques to planets in the habitable zones of low mass stars, uncovering detailed information about their orbits and surface/atmospheric properties. I discuss all of my results in the context of TRAPPIST-1, a nearby low mass star hosting seven transiting planets, three of which are in the habitable zone. This and similar soon-to-be discovered systems will likely revolutionize our understanding of exoplanets, habitability, and astrobiology in general
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