1,341 research outputs found
Conceptual Design of an In-Space Cryogenic Fluid Management Facility
The conceptual design of a Spacelab experiment to develop the technology associated with low gravity propellant management is presented. The proposed facility consisting of a supply tank, receiver tank, pressurization system, instrumentation, and supporting hardware, is described. The experimental objectives, the receiver tank to be modeled, and constraints imposed on the design by the space shuttle, Spacelab, and scaling requirements, are described. The conceptual design, including the general configurations, flow schematics, insulation systems, instrumentation requirements, and internal tank configurations for the supply tank and the receiver tank, is described. Thermal, structural, fluid, and safety and reliability aspects of the facility are analyzed. The facility development plan, including schedule and cost estimates for the facility, is presented. A program work breakdown structure and master program schedule for a seven year program are included
Conceptual design of an in-space cryogenic fluid management facility, executive summary
The conceptual design of a Spacelab experiment to develop the technology associated with low gravity propellant management is summarized. The preliminary facility definition, conceptual design and design analysis, and facility development plan, including schedule and cost estimates for the facility, are presented
The primordial deuterium abundance at z = 2.504 from a high signal-to-noise spectrum of Q1009+2956
The spectrum of the quasar Q1009+2956 has been observed
extensively on the Keck telescope. The Lyman limit absorption system was previously used to measure D/H by Burles & Tytler using a
spectrum with signal to noise approximately 60 per pixel in the continuum near
Ly {\alpha} at . The larger dataset now available combines
to form an exceptionally high signal to noise spectrum, around 147 per pixel.
Several heavy element absorption lines are detected in this LLS, providing
strong constraints on the kinematic structure. We explore a suite of absorption
system models and find that the deuterium feature is likely to be contaminated
by weak interloping Ly {\alpha} absorption from a low column density H I cloud,
reducing the expected D/H precision. We find D/H =
for this system. Combining this new
measurement with others from the literature and applying the method of Least
Trimmed Squares to a statistical sample of 15 D/H measurements results in a
"reliable" sample of 13 values. This sample yields a primordial deuterium
abundance of (D/H). The
corresponding mean baryonic density of the Universe is . The quasar absorption data is of the same precision as, and
marginally inconsistent with, the 2015 CMB Planck (TT+lowP+lensing)
measurement, . Further quasar and more
precise nuclear data are required to establish whether this is a random
fluctuation.Comment: accepted by MNRAS, 18 pages, 12 figures, 6 table
Shared Secret Places: Social Media and Affordances
The Social Media application Strava is used by exercisers to track running and cycling activities. Strava is carried with the exerciser and displays trophies and leaderboards to reward competitive performance. We were prompted by an auto-ethnographic account of Strava use to examine the way in which a particular stretch of running track around a lake showed up differently to the runner once Strava was integrated into their running practice. We look to Gibson’s relational notions of “affordances” and “niches” to understand this change in direct perception. We propose that these concepts have potential in helping us to research and understand the ways in which groups of Social Media users share and construct a similar experience of place in a way that is largely invisible to non-users. We consider some of the preliminary implications of this differentiated use of place and demonstrate the way in which a relational view of affordances helps us to make sense of this phenomenon
Evaluating the accuracy of facial expressions as emotion indicators across contexts in dogs
Facial expressions potentially serve as indicators of animal emotions if they are consistently present across situations that (likely) elicit the same emotional state. In a previous study, we used the Dog Facial Action Coding System (DogFACS) to identify facial expressions in dogs associated with conditions presumably eliciting positive anticipation (expectation of a food reward) and frustration (prevention of access to the food). Our first aim here was to identify facial expressions of positive anticipation and frustration in dogs that are context-independent (and thus have potential as emotion indicators) and to distinguish them from expressions that are reward-specific (and thus might relate to a motivational state associated with the expected reward). Therefore, we tested a new sample of 28 dogs with a similar set-up designed to induce positive anticipation (positive condition) and frustration (negative condition) in two reward contexts: food and toys. The previous results were replicated: Ears adductor was associated with the positive condition and Ears flattener, Blink, Lips part, Jaw drop, and Nose lick with the negative condition. Four additional facial actions were also more common in the negative condition. All actions except the Upper lip raiser were independent of reward type. Our second aim was to assess basic measures of diagnostic accuracy for the potential emotion indicators. Ears flattener and Ears downward had relatively high sensitivity but low specificity, whereas the opposite was the case for the other negative correlates. Ears adductor had excellent specificity but low sensitivity. If the identified facial expressions were to be used individually as diagnostic indicators, none would allow consistent correct classifications of the associated emotion. Diagnostic accuracy measures are an essential feature for validity assessments of potential indicators of animal emotion. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s10071-021-01532-1
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Influence of Heat-Treatment of Selective Laser Melting Products - e.g. Ti6Al4V
Usually additive manufactured metal parts are showing a different mechanical behavior compared to
conventionally produced parts used the same material. Apart from process-related macroscopic part
imperfections (pores, surface roughness, etc.) the microstructure has a decisive influence on the mechanical
properties of the materials. Thus, in order to optimize mechanical properties of metal parts a heat treatment for
changing microstructures is routinely applied in most production lines to meet the product requirements. By
means of the Titanium alloy Ti6Al4V the optimization of the static- and the fracture mechanical behavior by
changing the microstructure with a heat treatment after the SLM process is discussed on the present work.Mechanical Engineerin
Primordial deuterium abundance at z=2.504 towards Q1009+2956
The z_abs = 2.504 Lyman Limit absorption system (LLS) towards Q1009+2956 has
previously been used to estimate the primordial deuterium abundance. Since the
initial measurement by Burles & Tytler, this quasar has been observed
extensively with the Keck telescope, providing a substantial increase in
signal-to-noise (from 60 to 147 at continuum level of Ly-alpha at z_abs=2.504).
We explore a set of different models for the absorption system and find that
the deuterium feature is contaminated by Ly-alpha absorption from a low column
density H I cloud. This significantly limits precision to which one can
estimate the D/H ratio in this LLS. Our final result for this system D/H
=2.48^{+0.41}_{-0.35}*10^{-5} has the same relative uncertainty of 17% as the
previous estimate by Burles & Tytler despite the far higher signal-to-noise of
our dataset. A weighted mean of 13 D/H measurements available in the literature
(including our result) gives the primordial deuterium abundance of (D/H)_p =
(2.545 +/- 0.025)*10^{-5} and the corresponding baryon density of the Universe
of Omega_b h^2 = 0.02174 +/- 0.00025 marginally inconsistent with the 2015
Planck CMB data.Comment: 7 pages, 3 figures, conference proceedings from PhysicA.SPb 201
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