372 research outputs found
Atmospheric Profile Imprint in Firewall Ablation Coefficient
A general formula which expresses the distance along the meteoric fireball trajectory 1 as a function of t is discussed. Differential equations which include the motion and ablation of a single nonfragmenting meteor body are presented. The importance of the atmospheric density profile in the meteor formula is emphasized
Exploratory Analysis of Highly Heterogeneous Document Collections
We present an effective multifaceted system for exploratory analysis of
highly heterogeneous document collections. Our system is based on intelligently
tagging individual documents in a purely automated fashion and exploiting these
tags in a powerful faceted browsing framework. Tagging strategies employed
include both unsupervised and supervised approaches based on machine learning
and natural language processing. As one of our key tagging strategies, we
introduce the KERA algorithm (Keyword Extraction for Reports and Articles).
KERA extracts topic-representative terms from individual documents in a purely
unsupervised fashion and is revealed to be significantly more effective than
state-of-the-art methods. Finally, we evaluate our system in its ability to
help users locate documents pertaining to military critical technologies buried
deep in a large heterogeneous sea of information.Comment: 9 pages; KDD 2013: 19th ACM SIGKDD Conference on Knowledge Discovery
and Data Minin
On the association of the daytime Taurid complex meteor streams with asteroids
The Taurid meteor complex daytime streams Zeta Perseids and Beta Taurids are investigated from the viewpoint of their orbital evolution and relation to the streams of the preperihelion branch of the complex. A search for potential
co-parents among NEOs known until mid-June 2005 is made and two candidates for the association with the Zeta Perseids and two for the Beta Taurids are found. The Beta Taurids are shown to be postperihelion continuation of the Northern Taurids and Zeta Perseids are continuation of two complex filaments related to the Southern Taurids
Disolución de hierro de un concentrado complejo de esfalerita por Acidithiobacillus ferrooxidans
En el presente trabajo se empleó una cepa de Acidithiobacillus ferrooxidans (Af) para biolixiviar el hierro pirítico presente en un concentrado de sulfuro de zinc con un contenido de 1,41% en peso de hierro. El proceso de biolixiviación se llevó a cabo en una suspensión conteniendo de 5 a 8% de sólidos p/v a un pH de alrededor de 2,7 (ajustado con ácido sulfúrico) y a una temperatura de 30 °C. Los resultados muestran que en un periodo de 15 días, el contenido metalúrgico del hierro disminuyó en un 17%, lo cual se traduce en un incremento en el grado metalúrgico del concentrado de zinc de 64,6 a 66,9%, lo que permitió incrementar substancialmente el valor comercial de éste, evitando penalizaciones por el contenido de hierro presente
The SQM/COSMO filter: reliable native pose identification based on the quantum-mechanical description of protein–ligand interactions and implicit COSMO solvation
Current virtual screening tools are fast, but reliable scoring is elusive. Here, we present the "SQM/COSMO filter", a novel scoring function featuring a quantitative semiempirical quantum mechanical (SQM) description of all types of noncovalent interactions coupled with implicit COSMO solvation. We show unequivocally that it outperforms eight widely used scoring functions. The accuracy and chemical generality of the SQM/COSMO filter make it a perfect tool for late stages of virtual screening
Overview of VideoCLEF 2009: New perspectives on speech-based multimedia content enrichment
VideoCLEF 2009 offered three tasks related to enriching video content for improved multimedia access in a multilingual environment. For each task, video data (Dutch-language television, predominantly documentaries) accompanied by speech recognition transcripts were provided.
The Subject Classification Task involved automatic tagging of videos with subject theme labels. The best performance was achieved by approaching subject tagging as an information retrieval task and using both speech recognition transcripts and archival metadata. Alternatively, classifiers were trained using either the training data provided or data collected from Wikipedia or via general Web search. The Affect Task involved detecting narrative peaks, defined as points where viewers perceive heightened dramatic tension. The task was carried out on the “Beeldenstorm” collection containing 45 short-form documentaries on the visual arts. The best runs exploited affective vocabulary and audience directed speech. Other approaches included using topic changes, elevated speaking pitch, increased speaking intensity and radical visual changes. The Linking Task, also called “Finding Related Resources Across Languages,” involved linking video to material on the same subject in a different language.
Participants were provided with a list of multimedia anchors (short video segments) in the Dutch-language “Beeldenstorm” collection and were expected to return target pages drawn from English-language Wikipedia. The best performing methods used the transcript of the
speech spoken during the multimedia anchor to build a query to search an index of the Dutch language Wikipedia. The Dutch Wikipedia pages returned were used to identify related English pages. Participants also experimented with pseudo-relevance feedback, query translation and methods that targeted proper names
The daytime Taurid complex meteor streams: Activity and mass distribution
The activity and mass distribution of the summer daytime Taurid meteor complex streams Zeta Perseids and Beta Taurids in 1997-2004 is analysed and discussed. The results are based on radio observations obtained by the BLM
forward-scatter system (Italy-Slovakia) and by the Ondrejov backscatter meteor radar (Czech Republic). The observed positions of maxima of the streams are in a general agreement with previous analysis. The observations indicate a filamentary structure of the streams, the existence of which is supported also by the mass exponent values
Meteor showers of comet C/1917 F1 Mellish
December Monocerotids and November Orionids are weak but established annual
meteor showers active throughout November and December. Analysis of a high
quality orbits subset of the SonotaCo video meteor database shows that the
distribution of orbital elements, geocentric velocity and also the orbital
evolution of the meteors and potential parent body may imply a common origin
for these meteors coming from the parent comet C/1917 F1 Mellish. This is also
confirmed by the physical properties and activity of these shower meteors. An
assumed release of meteoroids at the perihelion of the comet in the past and
the sky-plane radiant distribution reveal that the December Monocerotid stream
might be younger than the November Orionids. A meteoroid transversal component
of ejection velocity at the perihelion must be larger than 100 m/s. A few
authors have also associated December Canis Minorids with the comet C/1917 F1
Mellish. However, we did not find any connection.Comment: 11 pages, 11 figures and 5 table
Application of an Equilibrium Vaporization Model to the Ablation of Chondritic and Achondritic Meteoroids
We modeled equilibrium vaporization of chondritic and achondritic materials
using the MAGMA code. We calculated both instantaneous and integrated element
abundances of Na, Mg, Ca, Al, Fe, Si, Ti, and K in chondritic and achondritic
meteors. Our results are qualitatively consistent with observations of meteor
spectra.Comment: 8 pages, 4 figures; in press, Earth, Moon, and Planets, Meteoroids
2004 conference proceeding
Asymptotic normalization coefficient of ^{8}B from breakup reactions and the S_{17} astrophysical factor
We show that asymptotic normalization coefficients (ANC) can be extracted
from one nucleon breakup reactions of loosely bound nuclei at 30-300 MeV/u. In
particular, the breakup of ^{8}B is described in terms of an extended Glauber
model. The 8B ANC extracted for the ground state of this nucleus from breakup
data at several energies and on different targets, C^2 = 0.450+/-0.039} fm^-1,
leads to the astrophysical factor S_{17}(0)= 17.4+/-1.5 eVb for the key
reaction for solar neutrino production 7Be(p,gamma)8B. The procedure described
here is more general, providing an indirect method to determine reaction rates
of astrophysical interest with beams of loosely bound radioactive nuclei.Comment: 4 pages, RevTex, 3 figures revised version to appear in Phys Rev Let
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