73 research outputs found
First detection of 22 GHz H2O masers in TX Camelopardalis
Simultaneous time monitoring observations of HO , SiO
= 1--0, 2--1, 3--2, and SiO = 0, = 1--0 lines were carried
out in the direction of the Mira variable star TX Cam with the Korean VLBI
Network single dish radio telescopes. For the first time, the HO maser
emission from TX Cam was detected near the stellar velocity at five epochs from
April 10, 2013 ( = 3.13) to June 4, 2014 ( = 3.89) including
minimum optical phases. The intensities of HO masers are very weak
compared to SiO masers. The variation of peak antenna temperature ratios among
SiO = 1, = 1--0, = 2--1, and = 3--2 masers is investigated
according to their phases. The shift of peak velocities of HO and SiO
masers with respect to the stellar velocity is also investigated according to
observed optical phases. The HO maser emission occurs around the stellar
velocity during our monitoring interval. On the other hand, the peak velocities
of SiO masers show a spread compared to the stellar velocity. The peak
velocities of SiO = 2--1, and = 3--2 masers show a smaller spread with
respect to the stellar velocity than those of SiO = 1--0 masers. These
simultaneous observations of multi-frequencies will provide a good constraint
for maser pumping models and a good probe for investigating the stellar
atmosphere and envelope according to their different excitation conditions.Comment: 10 page
Debiased Automatic Speech Recognition for Dysarthric Speech via Sample Reweighting with Sample Affinity Test
Automatic speech recognition systems based on deep learning are mainly
trained under empirical risk minimization (ERM). Since ERM utilizes the
averaged performance on the data samples regardless of a group such as healthy
or dysarthric speakers, ASR systems are unaware of the performance disparities
across the groups. This results in biased ASR systems whose performance
differences among groups are severe. In this study, we aim to improve the ASR
system in terms of group robustness for dysarthric speakers. To achieve our
goal, we present a novel approach, sample reweighting with sample affinity test
(Re-SAT). Re-SAT systematically measures the debiasing helpfulness of the given
data sample and then mitigates the bias by debiasing helpfulness-based sample
reweighting. Experimental results demonstrate that Re-SAT contributes to
improved ASR performance on dysarthric speech without performance degradation
on healthy speech.Comment: Accepted by Interspeech 202
Spatial dynamics of Maine lobster landings in a changing coastal system
Continued warming of oceans has caused global shifts in marine species distributions. This can result in changes in the spatial distribution of landings and have distributional impacts on marine resource-dependent communities. We evaluated the spatial dynamics of American lobster (Homarus americanus) landings in coastal Maine, which supports one of the most valuable U.S. fisheries. We coupled a bioclimate envelope model and a generalized additive model to project spatial dynamics of lobster landings under possible climate scenarios. This coupled model was then used to forecast future lobster habitat suitability based on IPCC RCP climate scenarios and predict distributions of fishery landings from this projected lobster habitat suitability. The historical spatial distribution of fishery landings shows the highest proportional landings in Maine’s Southern (southwest) regions. The current distribution of landings shows higher proportional landings in Downeast (northeast) regions with the highest proportional landings in Midcoast (middle) regions. Our results suggest that while the proportion of landings in each zone will remain stable, changes in habitat suitability in the spring and fall will reduce total landings. Future habitat suitability is projected to decrease in spring but increase in fall in Downeast areas. Downeast landings are projected to decrease in the next 30 years, then increase over the subsequent 80 years, depending on RCP scenarios and abundance regimes. Midcoast landings are projected to decrease while Southcoast landings are expected to stay constant. This study develops an approach to link climate change effects to fishery landings. These findings have long-term implications for sustainable, localized management of the Maine lobster fishery in a changing climate
Simultaneous VLBI Astrometry of H2O and SiO Masers toward the Semiregular Variable R Crateris
We obtained, for the first time, astrometrically registered maps of the 22.2
GHz H2O and 42.8, 43.1, and 86.2 GHz SiO maser emission toward the semiregular
b-type variable (SRb) R Crateris, at three epochs (2015 May 21, and 2016
January 7 and 26) using the Korean Very-long-baseline Interferometry Network.
The SiO masers show a ring-like spatial structure, while the H2O maser shows a
very asymmetric one-side outflow structure, which is located at the southern
part of the ring-like SiO maser feature. We also found that the 86.2 GHz SiO
maser spots are distributed in an inner region, compared to those of the 43.1
GHz SiO maser, which is different from all previously known distributions of
the 86.2 GHz SiO masers in variable stars. The different distribution of the
86.2 GHz SiO maser seems to be related to the complex dynamics caused by the
overtone pulsation mode of the SRb R Crateris. Furthermore, we estimated the
position of the central star based on the ring fitting of the SiO masers, which
is essential for interpreting the morphology and kinematics of a circumstellar
envelope. The estimated stellar coordinate corresponds well to the position
measured by Gaia
Algebraic Attacks on Summation Generators
We apply the algebraic attacks
on stream ciphers with memories to the summation generator.
For a summation generator that uses LFSRs, the
algebraic equation relating the key stream bits
and LFSR output bits
can be made to be of degree less than or equal to
, using
consecutive key stream bits.
This is much lower than the upper bound given by
previous general results
The First Very Long Baseline Interferometry Image of 44 GHz Methanol Maser with the KVN and VERA Array (KaVA)
We have carried out the first very long baseline interferometry (VLBI)
imaging of 44 GHz class I methanol maser (7_{0}-6_{1}A^{+}) associated with a
millimeter core MM2 in a massive star-forming region IRAS 18151-1208 with KaVA
(KVN and VERA Array), which is a newly combined array of KVN (Korean VLBI
Network) and VERA (VLBI Exploration of Radio Astrometry). We have succeeded in
imaging compact maser features with a synthesized beam size of 2.7
milliarcseconds x 1.5 milliarcseconds (mas). These features are detected at a
limited number of baselines within the length of shorter than approximately 650
km corresponding to 100 Mlambda in the uv-coverage. The central velocity and
the velocity width of the 44 GHz methanol maser are consistent with those of
the quiescent gas rather than the outflow traced by the SiO thermal line. The
minimum component size among the maser features is ~ 5 mas x 2 mas, which
corresponds to the linear size of ~ 15 AU x 6 AU assuming a distance of 3 kpc.
The brightness temperatures of these features range from ~ 3.5 x 10^{8} to 1.0
x 10^{10} K, which are higher than estimated lower limit from a previous Very
Large Array observation with the highest spatial resolution of ~ 50 mas. The 44
GHz class I methanol maser in IRAS 18151-1208 is found to be associated with
the MM2 core, which is thought to be less evolved than another millimeter core
MM1 associated with the 6.7 GHz class II methanol maser.Comment: 19 pages, 3 figure
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