378 research outputs found
Multi-label Ferns for Efficient Recognition of Musical Instruments in Recordings
In this paper we introduce multi-label ferns, and apply this technique for
automatic classification of musical instruments in audio recordings. We compare
the performance of our proposed method to a set of binary random ferns, using
jazz recordings as input data. Our main result is obtaining much faster
classification and higher F-score. We also achieve substantial reduction of the
model size
The effect of distraction on change detection in crowded acoustic scenes
In this series of behavioural experiments we investigated the effect of distraction on the maintenance of acoustic scene information in short-term memory. Stimuli are artificial acoustic ‘scenes’ composed of several (up to twelve) concurrent tone-pip streams (‘sources’). A gap (1000 ms) is inserted partway through the ‘scene’; Changes in the form of an appearance of a new source or disappearance of an existing source, occur after the gap in 50% of the trials. Listeners were instructed to monitor the unfolding ‘soundscapes’ for these events. Distraction was measured by presenting distractor stimuli during the gap. Experiments 1 and 2 used a dual task design where listeners were required to perform a task with varying attentional demands (‘High Demand’ vs. ‘Low Demand’) on brief auditory (Experiment 1a) or visual (Experiment 1b) signals presented during the gap. Experiments 2 and 3 required participants to ignore distractor sounds and focus on the change detection task. Our results demonstrate that the maintenance of scene information in short-term memory is influenced by the availability of attentional and/or processing resources during the gap, and that this dependence appears to be modality specific. We also show that these processes are susceptible to bottom up driven distraction even in situations when the distractors are not novel, but occur on each trial. Change detection performance is systematically linked with the, independently determined, perceptual salience of the distractor sound. The findings also demonstrate that the present task may be a useful objective means for determining relative perceptual salience
Detection of appearing and disappearing objects in complex acoustic scenes.
The ability to detect sudden changes in the environment is critical for survival. Hearing is hypothesized to play a major role in this process by serving as an "early warning device," rapidly directing attention to new events. Here, we investigate listeners' sensitivity to changes in complex acoustic scenes-what makes certain events "pop-out" and grab attention while others remain unnoticed? We use artificial "scenes" populated by multiple pure-tone components, each with a unique frequency and amplitude modulation rate. Importantly, these scenes lack semantic attributes, which may have confounded previous studies, thus allowing us to probe low-level processes involved in auditory change perception. Our results reveal a striking difference between "appear" and "disappear" events. Listeners are remarkably tuned to object appearance: change detection and identification performance are at ceiling; response times are short, with little effect of scene-size, suggesting a pop-out process. In contrast, listeners have difficulty detecting disappearing objects, even in small scenes: performance rapidly deteriorates with growing scene-size; response times are slow, and even when change is detected, the changed component is rarely successfully identified. We also measured change detection performance when a noise or silent gap was inserted at the time of change or when the scene was interrupted by a distractor that occurred at the time of change but did not mask any scene elements. Gaps adversely affected the processing of item appearance but not disappearance. However, distractors reduced both appearance and disappearance detection. Together, our results suggest a role for neural adaptation and sensitivity to transients in the process of auditory change detection, similar to what has been demonstrated for visual change detection. Importantly, listeners consistently performed better for item addition (relative to deletion) across all scene interruptions used, suggesting a robust perceptual representation of item appearance
Structure and physical properties of Na4C60 under ambient and high pressures
The structure and physical properties of two-dimensional polymeric Na4C60 (body-centered monoclinic, space group I2/m) are studied in a wide temperature region from 12 to 300 K at 1 bar, and in a pressure region up to 53 kbar at 300 K. The temperature dependence of lattice constants suggests a structural anomaly below 100 K where the variation of spin susceptibility is observed from electron spin resonance. The thermal expansion of the unit-cell volume V is smaller than that of monomeric Rb3C60 and K3C60. The compressibility of c is larger than that of a and b, which can be well explained by the repulsion between Na ions. The compressibility of the center-to-center distance in the (10(1) over bar) plane is similar to1/3 times smaller that that in the (101) plane, which can be well explained by the formation of the polymer chains. Further, a possibility of a three-dimensional polymerization is discussed on the basis of the pressure dependence of C-60. . .C-60 distances.</p
The Bright and Dark Sides of High-Redshift starburst galaxies from {\it Herschel} and {\it Subaru} observations
We present rest-frame optical spectra from the FMOS-COSMOS survey of twelve
\textit{Herschel} starburst galaxies, with Star Formation Rate
(SFR) elevated by 8, on average, above the star-forming Main Sequence
(MS). Comparing the H to IR luminosity ratio and the Balmer Decrement
we find that the optically-thin regions of the sources contain on average only
percent of the total SFR whereas percent comes from an
extremely obscured component which is revealed only by far-IR observations and
is optically-thick even in H. We measure the [NII]/H
ratio, suggesting that the less obscured regions have a metal content similar
to that of the MS population at the same stellar masses and redshifts. However,
our objects appear to be metal-rich outliers from the metallicity-SFR
anticorrelation observed at fixed stellar mass for the MS population. The
[SII]/[SII] ratio from the average spectrum indicates an
electron density , larger than what
estimated for MS galaxies but only at the 1.5 level. Our results
provide supporting evidence that high- MS outliers are the analogous of
local ULIRGs, and are consistent with a major merger origin for the starburst
event.Comment: 6 pages, 4 figures, Accepted for publication in ApJ Letter
Metal-insulator transition at 50 K in Na2C60
Temperature dependence of electron spin resonance in Na2C60 was studied in a temperature range from 2 to 350 K. It was shown that Na2C60 was metallic above 50 K and had a metal-insulator transition at 50 K. The center frequency for the Hg(2) Raman mode in Na2C60 at 298 K was close to those in the metallic Rb3C60, K3C60, and Cs3C60, while the linewidth was close to that in the metallic but nonsuperconducting Cs3C60. The Hg(2) mode showed a large blueshift and narrowing at 50 K. The center frequency and the linewidth in the low-temperature region from 50 K were almost the same as those in the insulating C-60 and Rb6C60, which showed the metal-insulator transition at 50 K in Na2C60. The origin of this metal-insulator transition was discussed in terms of the electron-phonon interaction (Jahn-Teller effect) and the electron-electron interaction (Mott-Hubbard picture). [S0163-1829(99)04123-5].</p
Fabrication of field-effect transistor device with higher fullerene, C<sub>88</sub>
A fullerene field-effect transistor (FET) device has been fabricated with thin films of C88, and n-channel normally-on depletion-type FET properties have been found in this FET device. The C88 FET exhibited a high mobility, μ, of 2.5 x 10-3 cm2 V-1 s-1 at 300 K, in fullerene FETs. The carrier transport showed a thermally-activated hopping transport. The n-channel normally-on FET properties and the hopping transport reflect the small mobility gap and low carrier concentration in the channel region of C88 thin-films.</p
Rest-frame Optical Emission Lines in Far-Infrared Selected Galaxies at z<1.7 from the FMOS-COSMOS Survey
We have used FMOS on Subaru to obtain near-infrared spectroscopy of 123
far-infrared selected galaxies in COSMOS and obtain the key rest-frame optical
emission lines. This is the largest sample of infrared galaxies with
near-infrared spectroscopy at these redshifts. The far-infrared selection
results in a sample of galaxies that are massive systems that span a range of
metallicities in comparison with previous optically selected surveys, and thus
has a higher AGN fraction and better samples the AGN branch. We establish the
presence of AGN and starbursts in this sample of (U)LIRGs selected as
Herschel-PACS and Spitzer-MIPS detections in two redshift bins (z~0.7 and
z~1.5) and test the redshift dependence of diagnostics used to separate AGN
from star-formation dominated galaxies. In addition, we construct a low
redshift (z~0.1) comparison sample of infrared selected galaxies and find that
the evolution from z~1.5 to today is consistent with an evolving AGN selection
line and a range of ISM conditions and metallicities from the models of Kewley
et al. (2013b). We find that a large fraction of (U)LIRGs are BPT-selected AGN
using their new, redshift-dependent classification line. We compare the
position of known X-ray detected AGN (67 in total) with the BPT selection and
find that the new classification line accurately selects most of these objects
(> 70%). Furthermore, we identify 35 new (likely obscured) AGN not selected as
such by their X-ray emission. Our results have direct implications for AGN
selection at higher redshift with either current (MOSFIRE, KMOS) or future
(PFS, MOONS) spectroscopic efforts with near-infrared spectral coverage.Comment: 7 pages, 3 figures, 2 tables. Accepted for publication in The
Astrophysical Journal Letter
A Multiwavelength Consensus on the Main Sequence of Star-Forming Galaxies at z~2
We compare various star formation rate (SFR) indicators for star-forming
galaxies at in the COSMOS field. The main focus is on the SFRs from
the far-IR (PACS-Herschel data) with those from the ultraviolet, for galaxies
selected according to the BzK criterion. FIR-selected samples lead to a vastly
different slope of the SFR-stellar mass () relation, compared to that of
the dominant main sequence population as measured from the UV, since the FIR
selection picks predominantly only a minority of outliers. However, there is
overall agreement between the main sequences derived with the two SFR
indicators, when stacking on the PACS maps the BzK-selected galaxies. The
resulting logarithmic slope of the SFR-{} relation is , in
agreement with that derived from the dust-corrected UV-luminosity. Exploiting
deeper 24m-Spitzer data we have characterized a sub-sample of galaxies
with reddening and SFRs poorly constrained, as they are very faint in the
band. The combination of Herschel with Spitzer data have allowed us to largely
break the age/reddening degeneracy for these intriguing sources, by
distinguishing whether a galaxy is very red in B-z because of being heavily
dust reddened, or whether because star formation has been (or is being)
quenched. Finally, we have compared our SFR(UV) to the SFRs derived by stacking
the radio data and to those derived from the H luminosity of a sample
of star-forming galaxies at . The two sets of SFRs are broadly
consistent as they are with the SFRs derived from the UV and by stacking the
corresponding PACS data in various mass bins.Comment: Accepted for publication in MNRA
Lagrangian drifter paths and length scales in the tropical Pacific warm pool from 1990 to 1991: with application of fractal techniques
International audienceThis paper presents an analysis of WOCE/TOGA surface drifter paths and its interpretation in conjunction with the west Pacific warm pool water motion. Our interest here lies in the existence of scale invariance in the observed data sets. The analysis proceeds by detecting scale invariance in the drifter paths data, and interpreting the invariance in terms of the statistical second order moment. The range of constant scaling exponent was found to be between 5 days and 10 days, and this range corresponded with the "long tail" of the temporal correlation function in the zonal direction. Velocity covariances in both the zonal and meridional directions were computed, and corresponding diffusivities were 8100 m2/sec meridionally and 41000 m2/sec zonally. Considering the existence of large scale mean flow, it is thought that self-similar energy cascade processes associated with constant scaling exponent may be responsible for the anomalous zonal diffusivity, while the meridional diffusivity may be approximated by ordinary Brownian processes. We suggest that the scale invariance of the WOCE/TOGA surface drifter paths may be a manifestation of energy cascade processes from large scale mean flow to smaller scale irregular flow that is represented by fractional Brownian motion in the zonal direction
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