6,878 research outputs found
Development of explosive welding techniques for fabrication of regeneratively cooled thrust chambers for large rocket engine requirements Final report, 28 Jun. 1967 - 15 Sep. 1970
Explosive welding techniques in fabricating regeneratively cooled thrust chambers for large rocket engine requirements including ultrasonic inspection, metallography, and burst testin
Testing Assumptions in Deliberative Democratic Design: A Preliminary Assessment of the Efficacy of the Participedia Data Archive as an Analytic Tool
At smaller social scales, deliberative democratic theory can be restated as an input-process-output model. We advance such a model to formulate hypotheses about how the context and design of a civic engagement process shape the deliberation that takes place therein, as well as the impact of the deliberation on participants and subsequent policymaking. To test those claims, we extract and code case studies from Participedia.net, a research platform that has adopted a self-directed crowd-sourcing strategy to collect data on participatory institutions and deliberative interventions around the world. We explain and confront the challenges faced in coding and analyzing the Participedia cases, which involves managing reliability issues and missing data. In spite of those difficulties, regression analysis of the coded cases shows compelling results, which provide considerable support for our general theoretical model. We conclude with reflections on the implications of our findings for deliberative theory, the design of democratic innovations, and the utility of Participedia as a data archive
Preliminary results using a P300 brain-computer interface speller: a possible interaction effect between presentation paradigm and set of stimuli
Fernández-Rodríguez Á., Medina-Juliá M.T., Velasco-Álvarez F., Ron-Angevin R. (2019) Preliminary Results Using a P300 Brain-Computer Interface Speller: A Possible Interaction Effect Between Presentation Paradigm and Set of Stimuli. In: Rojas I., Joya G., Catala A. (eds) Advances in Computational Intelligence. IWANN 2019. Lecture Notes in Computer Science, vol 11506. Springer, ChamSeveral proposals to improve the performance controlling a P300-based BCI speller have been studied using the standard row-column presentation (RCP) par-adigm. However, this paradigm could not be suitable for those patients with lack of gaze control. To solve that, the rapid serial visual presentation (RSVP) para-digm, which presents the stimuli located in the same position, has been proposed in previous studies. Thus, the aim of the present work is to assess if a stimuli set of pictures that improves the performance in RCP, could also improve the per-formance in a RSVP paradigm. Six participants have controlled four conditions in a calibration task: letters in RCP, pictures in RCP, letters in RSVP and pictures in RSVP. The results showed that pictures in RCP obtained the best accuracy and information transfer rate. The improvement effect given by pictures was greater in the RCP paradigm than in RSVP. Therefore, the improvements reached under RCP may not be directly transferred to the RSVP.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Non-Linear Effects in Non-Kerr spacetimes
There is a chance that the spacetime around massive compact objects which are
expected to be black holes is not described by the Kerr metric, but by a metric
which can be considered as a perturbation of the Kerr metric. These non-Kerr
spacetimes are also known as bumpy black hole spacetimes. We expect that, if
some kind of a bumpy black hole exists, the spacetime around it should possess
some features which will make the divergence from a Kerr spacetime detectable.
One of the differences is that these non-Kerr spacetimes do not posses all the
symmetries needed to make them integrable. We discuss how we can take advantage
of this fact by examining EMRIs into the Manko-Novikov spacetime.Comment: 8 pages, 3 Figures; to appear in the proceedings of the conference
"Relativity and Gravitation: 100 Years after Einstein in Prague" (2012
Tree-Independent Dual-Tree Algorithms
Dual-tree algorithms are a widely used class of branch-and-bound algorithms.
Unfortunately, developing dual-tree algorithms for use with different trees and
problems is often complex and burdensome. We introduce a four-part logical
split: the tree, the traversal, the point-to-point base case, and the pruning
rule. We provide a meta-algorithm which allows development of dual-tree
algorithms in a tree-independent manner and easy extension to entirely new
types of trees. Representations are provided for five common algorithms; for
k-nearest neighbor search, this leads to a novel, tighter pruning bound. The
meta-algorithm also allows straightforward extensions to massively parallel
settings.Comment: accepted in ICML 201
The Evolving Faint-End of the Luminosity Function
We investigate the evolution of the faint-end slope of the luminosity
function, , using semi-analytical modeling of galaxy formation. In
agreement with observations, we find that the slope can be fitted well by
, with a=-1.13 and b=-0.1. The main driver for the evolution
in is the evolution in the underlying dark matter mass function.
Sub-L_* galaxies reside in dark matter halos that occupy a different part of
the mass function. At high redshifts, this part of the mass function is steeper
than at low redshifts and hence is steeper. Supernova feedback in
general causes the same relative flattening with respect to the dark matter
mass function. The faint-end slope at low redshifts is dominated by field
galaxies and at high redshifts by cluster galaxies. The evolution of
in each of these environments is different, with field galaxies
having a slope b=-0.14 and cluster galaxies b=-0.05. The transition from
cluster-dominated to field-dominated faint-end slope occurs roughly at a
redshift , and suggests that a single linear fit to the overall
evolution of might not be appropriate. Furthermore, this result
indicates that tidal disruption of dwarf galaxies in clusters cannot play a
significant role in explaining the evolution of at z< z_*. In
addition we find that different star formation efficiencies a_* in the
Schmidt-Kennicutt-law and supernovae-feedback efficiencies generally
do not strongly influence the evolution of .Comment: 4 pages, replaced with version accepted to ApJL, minor changes to
figure
Galaxy Mergers at z>1 in the HUDF: Evidence for a Peak in the Major Merger Rate of Massive Galaxies
We present a measurement of the galaxy merger fraction and number density
from observations in the Hubble Ultra Deep Field for 0.5<z<2.5. We fit the
combination of broadband data and slitless spectroscopy of 1308 galaxies with
stellar population synthesis models to select merging systems based on a
stellar mass of >10^10 M_sol. When correcting for mass incompleteness, the
major merger fraction is not simply proportional to (1+z)^m, but appears to
peak at z_frac~=1.3+-0.4. From this merger fraction, we infer that ~42% of
massive galaxies have undergone a major merger since z~1. We show that the
major merger number density peaks at z_dens~1.2, which marks the epoch where
major merging of massive galaxies is most prevalent. This critical redshift is
comparable to the peak of the cosmic star formation rate density, and occurs
roughly 2.6 Gyr earlier in cosmic time than the peak in the number density of
X-ray selected active galactic nuclei. These observations support an indirect
evolutionary link between merging, starburst, and active galaxies.Comment: Accepted to ApJ. 7 pages, 6 figures, 1 table. Uses and includes
emulateapj.cls. In the initial submission, Figures 1 and 2 where switche
Quantum Cosmology of Kantowski-Sachs like Models
The Wheeler-DeWitt equation for a class of Kantowski-Sachs like models is
completely solved. The generalized models include the Kantowski-Sachs model
with cosmological constant and pressureless dust. Likewise contained is a
joined model which consists of a Kantowski-Sachs cylinder inserted between two
FRW half--spheres. The (second order) WKB approximation is exact for the wave
functions of the complete set and this facilitates the product structure of the
wave function for the joined model. In spite of the product structure the wave
function can not be interpreted as admitting no correlations between the
different regions. This problem is due to the joining procedure and may
therefore be present for all joined models. Finally, the {s}ymmetric {i}nitial
{c}ondition (SIC) for the wave function is analyzed and compared with the ``no
bouindary'' condition. The consequences of the different boundary conditions
for the arrow of time are briefly mentioned.Comment: 21 pages, uses LaTeX2e, epsf.sty and float.sty, three figures (50
kb); changes: one figure added, new interpretation of quantizing procedure
for the joined model and many minor change
Students’ Modular Learning Experiences Amidst Pandemic: A Basis for Recovery Plan
The researchers of this study determined the experiences of students to modular learning, the things that they like most about the module, and the students’ priorities for the improvement of the module. The researchers employed the descriptive-survey design and the subjects of this study were 102 officially enrolled Grade 11 and Grade 12 Academic and TVL students of Juban National High School during the school year 2021-2022 and used adopted questionnaire. Findings revealed that the majority of the respondents had positive responses about the quality of the module. Moreover, there are things that the students like most about the module. Still, they have priorities to improve the module. The researchers recommended that the continuous improvement of the learning module must be done across the subject areas. Keywords: Modular Learning, COVID-19 Pandemic, Learning Experiences, Recovery Plan DOI: 10.7176/JEP/14-7-03 Publication date:March 31st 202
Constraining the Distribution of L- & T-Dwarfs in the Galaxy
We estimate the thin disk scale height of the Galactic population of L- &
T-dwarfs based on star counts from 15 deep parallel fields from the Hubble
Space Telescope. From these observations, we have identified 28 candidate L- &
T- dwarfs based on their (i'-z') color and morphology. By comparing these star
counts to a simple Galactic model, we estimate the scale height to be 350+-50
pc that is consistent with the increase in vertical scale with decreasing
stellar mass and is independent of reddening, color-magnitude limits, and other
Galactic parameters. With this refined measure, we predict that less than 10^9
M_{sol} of the Milky Way can be in the form L- & T- dwarfs, and confirm that
high-latitude, z~6 galaxy surveys which use the i'-band dropout technique are
97-100% free of L- & T- dwarf interlopers.Comment: 4 pages, 4 figures, accepted to ApJ
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