436 research outputs found
Integration over song classification replicates: Song variant analysis in the hihi
Human expert analyses are commonly used in bioacoustic studies and can potentially limit the reproducibility of these results. In this paper, a machine learning method is presented to statistically classify avian vocalizations. Automated approaches were applied to isolate bird songs from long field recordings, assess song similarities, and classify songs into distinct variants. Because no positive controls were available to assess the true classification of variants, multiple replicates of automatic classification of song variants were analyzed to investigate clustering uncertainty. The automatic classifications were more similar to the expert classifications than expected by chance. Application of these methods demonstrated the presence of discrete song variants in an island population of the New Zealand hihi (Notiomystis cincta). The geographic patterns of song variation were then revealed by integrating over classification replicates. Because this automated approach considers variation in song variant classification, it reduces potential human bias and facilitates the reproducibility of the results
Long-Term Variations in the Growth and Decay Rates of Sunspot Groups
Using the combined Greenwich (1874-1976) and Solar Optical Observatories
Network (1977-2009) data on sunspot groups, we study the long-term variations
in the mean daily rates of growth and decay of sunspot groups. We find that the
minimum and the maximum values of the annually averaged daily mean growth rates
are ~52% per day and ~183% per day, respectively, whereas the corresponding
values of the annually averaged daily mean decay rates are ~21% per day and
~44% per day, respectively. The average value (over the period 1874-2009) of
the growth rate is about 70% more than that of the decay rate. The growth and
the decay rates vary by about 35% and 13%, respectively, on a 60-year
time-scale. From the beginning of Cycle 23 the growth rate is substantially
decreased and near the end (2007-2008) the growth rate is lowest in the past
about 100 years.Comment: 1 table, 13 figures, accepted by Solar Physic
The G-O Rule and Waldmeier Effect in the Variations of the Numbers of Large and Small Sunspot Groups
We have analysed the combined Greenwich and Solar Optical Observing Network
(SOON) sunspot group data during the period of 1874-2011 and determined
variations in the annual numbers (counts) of the small, large and big sunspot
groups (these classifications are made on the basis of the maximum areas of the
sunspot groups). We found that the amplitude of an even-numbered cycle of the
number of large groups is smaller than that of its immediately following
odd-numbered cycle. This is consistent with the well known Gnevyshev and Ohl
rule or G-O rule of solar cycles, generally described by using the Zurich
sunspot number (Rz). During cycles 12-21 the G-O rule holds good for the
variation in the number of small groups also, but it is violated by cycle pair
(22, 23) as in the case of Rz. This behaviour of the variations in the small
groups is largely responsible for the anomalous behaviour of Rz in cycle pair
(22, 23). It is also found that the amplitude of an odd-numbered cycle of the
number of small groups is larger than that of its immediately following
even-numbered cycle. This can be called as `reverse G-O rule'. In the case of
the number of the big groups, both cycle pairs (12, 13) and (22, 23) violated
the G-O rule. In many cycles the positions of the peaks of the small, large,
and big groups are different and considerably differ with respect to the
corresponding positions of the Rz peaks. In the case of cycle 23, the
corresponding cycles of the small and large groups are largely symmetric/less
asymmetric (Waldmeier effect is weak/absent) with their maxima taking place two
years later than that of Rz. The corresponding cycle of the big groups is more
asymmetric (strong Waldmeier effect) with its maximum epoch taking place at the
same time as that of Rz.Comment: 13 pages, 5 figures, 1 table, accepted by Solar Physic
On the structure and evolution of a polar crown prominence/filament system
Polar crown prominences are made of chromospheric plasma partially circling
the Suns poles between 60 and 70 degree latitude. We aim to diagnose the 3D
dynamics of a polar crown prominence using high cadence EUV images from the
Solar Dynamics Observatory (SDO)/AIA at 304 and 171A and the Ahead spacecraft
of the Solar Terrestrial Relations Observatory (STEREO-A)/EUVI at 195A. Using
time series across specific structures we compare flows across the disk in 195A
with the prominence dynamics seen on the limb. The densest prominence material
forms vertical columns which are separated by many tens of Mm and connected by
dynamic bridges of plasma that are clearly visible in 304/171A two-color
images. We also observe intermittent but repetitious flows with velocity 15
km/s in the prominence that appear to be associated with EUV bright points on
the solar disk. The boundary between the prominence and the overlying cavity
appears as a sharp edge. We discuss the structure of the coronal cavity seen
both above and around the prominence. SDO/HMI and GONG magnetograms are used to
infer the underlying magnetic topology. The evolution and structure of the
prominence with respect to the magnetic field seems to agree with the filament
linkage model.Comment: 24 pages, 14 figures, Accepted for publication in Solar Physics
Journal, Movies can be found at http://www2.mps.mpg.de/data/outgoing/panesar
Work-integrated-learning within undergraduate science degree programs: case studies in assessment.
Employability is an important outcome for students enrolled in university degree programs. A challenge in generalist degrees like the Bachelor of Science (BSc) is that the program is not focused on qualifying graduates for a specific profession, and the curricula often feature limited transferable and employment skills. Work-integrated-learning (WIL) within BSc curriculums aims to develop graduates' employability skills, which are supported by authentic assessment tasks. This paper provides a number of case studies that highlight assessment within WIL subjects in BSc degrees at Australian universities. Across Queensland and Northern New South Wales universities, WIL is imbedded into the BSc curricula via placements, projects, field experience, work simulations, entrepreneurship and reflections on current work practices. Across different universities within this group, assessment typically contains multiple opportunities for reflection. In general, most assessment incorporates an early proposal outlining the tasks to be undertaken, reflection during the industry focused activity and a final written reflection that is often supported by an oral presentation. These case studies demonstrate the use of authentic assessment which is primarily focused on the link between transferable skills developed at university and the area of employability. Development of assessment, following reflection, should ensure that authentic, industry driven tasks are incorporated into any WIL subject
Triggering an eruptive flare by emerging flux in a solar active-region complex
A flare and fast coronal mass ejection originated between solar active
regions NOAA 11514 and 11515 on July 1, 2012 in response to flux emergence in
front of the leading sunspot of the trailing region 11515. Analyzing the
evolution of the photospheric magnetic flux and the coronal structure, we find
that the flux emergence triggered the eruption by interaction with overlying
flux in a non-standard way. The new flux neither had the opposite orientation
nor a location near the polarity inversion line, which are favorable for strong
reconnection with the arcade flux under which it emerged. Moreover, its flux
content remained significantly smaller than that of the arcade (approximately
40 %). However, a loop system rooted in the trailing active region ran in part
under the arcade between the active regions, passing over the site of flux
emergence. The reconnection with the emerging flux, leading to a series of jet
emissions into the loop system, caused a strong but confined rise of the loop
system. This lifted the arcade between the two active regions, weakening its
downward tension force and thus destabilizing the considerably sheared flux
under the arcade. The complex event was also associated with supporting
precursor activity in an enhanced network near the active regions, acting on
the large-scale overlying flux, and with two simultaneous confined flares
within the active regions.Comment: Accepted for publication in Topical Issue of Solar Physics: Solar and
Stellar Flares. 25 pages, 12 figure
Perception of Relative Depth Interval: Systematic Biases in Perceived Depth
Given an estimate of the binocular disparity between a pair of points and an estimate of the viewing distance, or knowledge of eye position, it should be possible to obtain an estimate of their depth separation. Here we show that, when points are arranged in different vertical geometric configurations across two intervals, many observers find this task difficult. Those who can do the task tend to perceive the depth interval in one configuration as very different from depth in the other configuration. We explore two plausible explanations for this effect. The first is the tilt of the empirical vertical horopter: Points perceived along an apparently vertical line correspond to a physical line of points tilted backwards in space. Second, the eyes can rotate in response to a particular stimulus. Without compensation for this rotation, biases in depth perception would result. We measured cyclovergence indirectly, using a standard psychophysical task, while observers viewed our depth configuration. Biases predicted from error due either to cyclovergence or to the tilted vertical horopter were not consistent with the depth configuration results. Our data suggest that, even for the simplest scenes, we do not have ready access to metric depth from binocular disparity.</jats:p
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