20,829 research outputs found
Heating analysis for the Pioneer Venus multiprobe mission
The fully coupled, radiating flow field around the entry probes is determined from a detailed calculation which includes equilibrium chemistry, nongray radiative transport, ablation product injection, and a laminar or turbulent boundary layer. Results show that the radiative flux toward the body is attenuated in the boundary layer at downstream regions of the body as well as at the stagnation point and that, even when radiation absorption by ablation products is accounted for, the radiative heating rates along the downstream regions of the body can, under certain conditions, exceed the stagnation point values. It is also shown that, for Venusian entry, the spectral distribution of radiative flux and the magnitude of radiation absorption by ablation products depend strongly on entry velocity, and that the state of the boundary layer can significantly influence the amount of ablation product absorption or emission that occurs in various spectral regions
Identifying the Host Galaxy of Gravitational Wave Signals
One of the goals of the current LIGO-GEO-Virgo science run is to identify
transient gravitational wave (GW) signals in near real time to allow follow-up
electromagnetic (EM) observations. An EM counterpart could increase the
confidence of the GW detection and provide insight into the nature of the
source. Current GW-EM campaigns target potential host galaxies based on overlap
with the GW sky error box. We propose a new statistic to identify the most
likely host galaxy, ranking galaxies based on their position, distance, and
luminosity. We test our statistic with Monte Carlo simulations of GWs produced
by coalescing binaries of neutron stars (NS) and black holes (BH), one of the
most promising sources for ground-based GW detectors. Considering signals
accessible to current detectors, we find that when imaging a single galaxy, our
statistic correctly identifies the true host ~20% to ~50% of the time,
depending on the masses of the binary components. With five narrow-field images
the probability of imaging the true host increases to ~50% to ~80%. When
collectively imaging groups of galaxies using large field-of-view telescopes,
the probability improves to ~30% to ~60% for a single image and to ~70% to ~90%
for five images. For the advanced generation of detectors (c. 2015+), and
considering binaries within 100 Mpc (the reach of the galaxy catalogue used),
the probability is ~40% for one narrow-field image, ~75% for five narrow-field
images, ~65% for one wide-field image, and ~95% for five wide-field images,
irrespective of binary type.Comment: 5 pages, 2 figure
An experimental study of the oxidation of graphite in high-temperature supersonic and hypersonic environments
Graphite oxidation in high temperature supersonic and hypersonic streams of air and air-nitrogen mixture
Experimental L-band SST satellite communications/surveillance terminal study. Volume 1 - Study summary
Study of design for experimental L band supersonic transport communications/surveillance termina
The Rocketdyne Multifunction Tester. Part 1: Test Method
The Rocketdyne Multifunction Tester is a general purpose test apparatus which utilizes axial and radial magnetic bearings as shaft excitation devices. The tester is modular in design so that different seal and bearing packages can be tested on the same test stand. The tester will be used for rotordynamic coefficient extraction, as well as life and fluid/material compatibility evaluations. Use of a magnetic bearing as a shaft excitation device opens up many possibilities for shaft excitation and rotordynamic coefficient extraction. In addition to describing the basic apparatus, some of the excitation and extraction methods are described. Some of the excitation methods to be discussed include random, aperiodic, harmonic, impulse and chirp
Not just for Christmas
This is the working paper for the project ‘Not Just for Christmas: consumption, popular culture and religious observance’.
This workshop engages academic and non-academic participants in the discussion of issues surrounding ethical responses to visual culture, consumption, and their embedding in moral and religious narratives at Christmas. The interdisciplinary workshop will, through a series of events, bring diverse scholars together to critically explore the ethical dilemmas faced in contemporary cultural experience of Christmas and open a positive dialogue over how such choices are informed by popular culture and also expressed through religious symbolism and ritual. The overlapping layers of this debate, intensified during the festive season of Christmas, will be related to sustainability and ethical consumption in daily life.
The project recognises the following intersections of consumption, popular culture and religious observance:
- Broadcasting, advertising and marketing employ the reflexive ethical awareness of consumers, often expressed through resistance
- Ethical approaches to Christmas are often led by religious or charitable organisations, yet also embrace wider issues relating to all consumption
- Embedded or nested narratives of Christmas in visual culture are often appreciated independently from their religious origins, yet are nonetheless historically reliant upon them
- Ethical or spiritual concerns of consumers are translated into, or appropriated from, Christmas traditions, rituals, objects, spaces and narratives
The complex issues raised by these intersections are illustrated in media approaches to Christmas, in the religious symbolism and liturgical practices of Advent and Christmas, as well as by consumer practices and in the spaces of consumption. The workshop will, using a mixture of academic and non-academic participants, object-led and online discussion, discursive publication and public feedback, reveal flashlight issues which will offer new areas of research and inquiry, as well as provide a necessary reappraisal of Christmas in light of changing societal impulses and needs. The workshop events respond to and address complex debates which may transcend religious belief but which often rely upon shared conceptions. Such debates cover the commercialisation of Christmas and other religious festivals in the context of ethical consumption practices including Fair Trade, charity donations, gift-giving alternatives and greeting cards.
The intellectual contribution of the project will be an informed ‘user guide’ to ethical consumption and the moral and spiritual issues it raises every day, guided by serious and sustained critical debate around Christmas. This guidance will be disseminated through the archived online forum and symposium, as well as the project’s webpage. Central to this is a ‘working paper’, written in plain language for a wide audience, which will report on the critical discussion of ethical consumption, Christian narratives, and visual/popular culture. The paper frames the guidance that these discussions have for viewers, consumers and religious practitioners in making ethical choices in daily life, and not just for Christmas
The Dreaming Variational Autoencoder for Reinforcement Learning Environments
Reinforcement learning has shown great potential in generalizing over raw
sensory data using only a single neural network for value optimization. There
are several challenges in the current state-of-the-art reinforcement learning
algorithms that prevent them from converging towards the global optima. It is
likely that the solution to these problems lies in short- and long-term
planning, exploration and memory management for reinforcement learning
algorithms. Games are often used to benchmark reinforcement learning algorithms
as they provide a flexible, reproducible, and easy to control environment.
Regardless, few games feature a state-space where results in exploration,
memory, and planning are easily perceived. This paper presents The Dreaming
Variational Autoencoder (DVAE), a neural network based generative modeling
architecture for exploration in environments with sparse feedback. We further
present Deep Maze, a novel and flexible maze engine that challenges DVAE in
partial and fully-observable state-spaces, long-horizon tasks, and
deterministic and stochastic problems. We show initial findings and encourage
further work in reinforcement learning driven by generative exploration.Comment: Best Student Paper Award, Proceedings of the 38th SGAI International
Conference on Artificial Intelligence, Cambridge, UK, 2018, Artificial
Intelligence XXXV, 201
RECYCLED SUBSTRATES: PLANT BIOMASS AND PLANT COVER CORRELATION
Green roofs extend roof membrane life and reduce waste to landfills. However, green roof costs must be reduced if their benefits are to accrue more widely. Use of recycled materials may reduce costs and also keep those materials out of landfills. Some work has been done on use of local recycled materials for green roof substrates, but none describe the characteristics, proportions and results of using an entire suite of blended recycled materials in admixtures (i.e., mixtures of very different materials) such as crumb rubber (CR), crushed used brick (CB) and compost (CPT) in concert with greens grade sand (#10), biochar (B) and topsoil inoculum (T). How does plant growth and performance on recycled substrates compare with a typical expanded shale and clay (ESC) substrate?
Two main techniques for measuring performance of green roof treatments are plant biomass and plant coverage. Both measure plant growth and performance, while coverage specifically addresses FLL (Forschungsgesellschaft Landschaftsentwicklung Landschaftsbau Guidelines for the Planning, Construction and Maintenance of Green Roofing) standards. This research project tested native plants on recycled substrate admixtures to assess the correlation between these two measures. It was found that the biomass and cover were strongly correlated at 0.665 (P \u3c.0001). Recycled substrate admixtures were found to be heavier, hold less water and had significantly less biomass and cover than the proprietary green roof substrate used as a control, but their native plantings still held the substrate in place. It is suggested that compost is a key ingredient for biomass production and future recycled green roof substrate might use recycled crumb rubber, biochar and compost for lighter substrate loading
Landscape Ecology of Hedgerows and Fencerows in Panama Township, Lancaster County, Nebraska
This study investigated woody plant composition, structure, and biomass of hedgerows and fencerows, and for effects between human attitudes and management practices; Fencerows arise as narrow strips of woody and herbaceous plants at field margins and property boundaries. Hedgerows grow from intentional linear plantings. Exotic species were more important in fencerow composition. Hackberry, Missouri gooseberry, American plum, and white mulberry readily inhabited both fencerows and hedgerows. Woody plants exhibited clumped distribution in both hedgerows and fencerows. A moisture gradient emerged as a factor in distribution of species. Management caused a significant difference in species richness and biomass in both hedgerows and fencerows. Hedgerows (discounting basal area of Osage-orange) had less tree biomass than fencerows and were more evenly distributed between center and margin. For all hedgerows, there was a significant difference between management schemes based on preservation-removal attitude scores
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