213 research outputs found
Introduction of Fractal Dimension Feature and Reduction of Calculation Amount in Person Authentication Using Evoked EEG by Ultrasound
The aim of this study is to authenticate individuals using an electroencephalogram (EEG) evoked by a stimulus. EEGs are highly confidential and enable continuous authentication during the use of or access to the given information or service. However, perceivable stimulation distracts the users from the activity they are carrying out while using the service. Therefore, ultrasound stimuli were chosen for EEG evocation. In our previous study, an Equal Error Rate (EER) of 0 % was achieved; however, there were some features which had not been evaluated. In this paper, we introduce a new type of feature, namely fractal dimension, as a nonlinear feature, and evaluate its verification performance on its own and in combination with other conventional features. As a result, an EER of 0 % was achieved when using five features and 14 electrodes, which accounted for 70 support vector machine (SVM) models. However, the construction of the 70 SVM models required extensive calculations. Thus, we reduced the number of SVM models to 24 while maintaining an EER = 0 %
Introduction of a Mutual Feature between Electrodes into Support Vector Machine Based Person Verification Using Evoked Electroencephalogram by Ultrasound
In user management, to realize continuous user authentication, we study the use of an electroencephalogram (EEG) evoked by ultrasound as biometrics. In previous studies, using a spectrum and four nonlinear quantities in EEG as individual features and a support vector machine (SVM) as a verification method achieved an equal error rate (EER) of 0 %. However, it required a large number of SVM models, wherein considerable amount of computation regarding learning was consumed. In this study, we introduce a mutual feature between electrodes and confirm its effectiveness in achieving EER = 0 % with a smaller number of SVM models
ASTE Simultaneous HCN(4-3) and HCO+(4-3) Observations of the Two Luminous Infrared Galaxies NGC 4418 and Arp 220
We report the results of HCN(J=4-3) and HCO+(J=4-3) observations of two
luminous infrared galaxies (LIRGs), NGC 4418 and Arp 220, made using the
Atacama Submillimeter Telescope Experiment (ASTE). The ASTE wide-band
correlator provided simultaneous observations of HCN(4-3) and HCO+(4-3) lines,
and a precise determination of their flux ratios. Both galaxies showed high
HCN(4-3) to HCO+(4-3) flux ratios of >2, possibly due to AGN-related phenomena.
The J = 4-3 to J = 1-0 transition flux ratios for HCN (HCO+) are similar to
those expected for fully thermalized (sub-thermally excited) gas in both
sources, in spite of HCN's higher critical density. If we assume collisional
excitation and neglect an infrared radiative pumping process, our non-LTE
analysis suggests that HCN traces gas with significantly higher density than
HCO+. In Arp 220, we separated the double-peaked HCN(4-3) emission into the
eastern and western nuclei, based on velocity information. We confirmed that
the eastern nucleus showed a higher HCN(4-3) to HCN(1-0) flux ratio, and thus
contained a larger amount of highly excited molecular gas than the western
nucleus.Comment: 21 pages, 4 figures, accepted for publication in PASJ (Vol.62, No.1,
2010 Feb 25 issue
Correlation Analysis of Features for Fusing in User Verification Using EEG Evoked by Ultrasound
In user verification using electroencephalograms (EEGs) evoked by ultrasound, an error rate of 0% was achieved. However, to achieve this, the classifiers for the number of features multiplied by the number of electrodes must be learned. Therefore, reducing the number of classifiers is crucial and must be achieved. This study confirmed that the random selection of features and electrodes facilitates further reduction in the number of classifiers. Random selection is equivalent to evenly selecting electrodes for each feature and electrode position. Consequently, the effectiveness of even selection was statistically confirmed. Furthermore, even selection resulted in the fusion of uncorrelated features. Thus, four statistical values of an EEG were introduced, and the effectiveness of fusing uncorrelated (independent) features was confirmed
ASTE CO(3--2) Survey of Elliptical Galaxies
We report CO(3--2) observations of 15 nearby elliptical galaxies
carried out with the ASTE telescope. Thirteen were selected without regard to
the presence of other tracers of cold interstellar matter. CO emission was
detected from three of the galaxies, two of which are undetected by IRAS at 100
microns, suggesting that cold ISM may be present in more ellipticals than
previously thought. The molecular gas masses range from to
. The ratio of the CO(3--2) and (1--0) lines,
, has a lower value for elliptical galaxies than for spiral galaxies
except for NGC 855, for which the value is close to the mean for spirals. The
molecular gas in NGC 855 has a mean density in the range 300 -- 1000 cm
adopting a temperature range of 15 -- 100 K.Comment: 6 pages, 3 figures, Accepted for publication in PAS
ASTE observations of nearby galaxies: A tight correlation between CO(J=3-2) emission and Halpha
Star formation rates (SFRs) obtained via extinction corrected H alpha are
compared to dense gas as traced by CO(J=3-2) emission at the centers of nearby
galaxies, observed with the ASTE telescope. It is found that, although many of
the observed positions are dusty and therefore heavily absorbed at H alpha, the
SFR shows a striking correlation with dense gas in the form of the Schmidt law
with an index 1.0. The correlation is also compared between gas traced by
CO(J=1-0) and application of H alpha extinction correction. We find that dense
gas produces a far better correlation with SFR in view of surface density
values.Comment: 6 pages, PASJ accepte
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