28,346 research outputs found
Relevance of Abelian Symmetry and Stochasticity in Directed Sandpiles
We provide a comprehensive view on the role of Abelian symmetry and
stochasticity in the universality class of directed sandpile models, in context
of the underlying spatial correlations of metastable patterns and scars. It is
argued that the relevance of Abelian symmetry may depend on whether the dynamic
rule is stochastic or deterministic, by means of the interaction of metastable
patterns and avalanche flow. Based on the new scaling relations, we conjecture
critical exponents for avalanche, which is confirmed reasonably well in
large-scale numerical simulations.Comment: 4 pages, 3 figures; published versio
Sedentary behaviors and adiposity in young people: causality and conceptual model
Research on sedentary behavior and adiposity in youth dates back to the 1980s. Sedentary behaviors, usually screen time, can be associated with adiposity. Although the association usually is small but significant, the field is complex, and results are dependent on what sedentary behaviors are assessed and may be mediated and moderated by other behaviors
Universality classes and crossover behaviors in non-Abelian directed sandpiles
We study universality classes and crossover behaviors in non-Abelian directed
sandpile models, in terms of the metastable pattern analysis. The non-Abelian
property induces spatially correlated metastable patterns, characterized by the
algebraic decay of the grain density along the propagation direction of an
avalanche. Crossover scaling behaviors are observed in the grain density due to
the interplay between the toppling randomness and the parity of the threshold
value. In the presence of such crossovers, we show that the broadness of the
grain distribution plays a crucial role in resolving the ambiguity of the
universality class. Finally, we claim that the metastable pattern analysis is
important as much as the conventional analysis of avalanche dynamics.Comment: 10 pages, 7 figures, 1 table; published in PRE as the full paper of
PRL v101, 218001 (2008
The Milky Way's stellar halo - lumpy or triaxial?
We present minimum chi-squared fits of power law and Hernquist density
profiles to F-turnoff stars in eight 2.5 deg wide stripes of SDSS data: five in
the North Galactic Cap and three in the South Galactic cap. Portions of the
stellar Galactic halo that are known to contain large streams of tidal debris
or other lumpy structure, or that may include significant contamination from
the thick disk, are avoided. The data strongly favor a model that is not
symmetric about the Galaxy's axis of rotation. If included as a free parameter,
the best fit to the center of the spheroid is surprisingly approx 3 kpc from
the Galactic center in the direction of the Sun's motion. The model fits favor
a low value of the density of halo stars at the solar position. The alternative
to a non-axisymmetric stellar distribution is that our fits are contaminated by
previously unidentified lumpy substructure.Comment: 10 pages, 10 figs, to appear in proceedings of conference "Physics at
the end of the Galactic Cosmic Ray Spectrum", Journal of Physics: Conf.
series, eds. G. Thomson and P. Sokolsk
Measuring the Hidden Aspects of Solar Magnetism
2008 marks the 100th anniversary of the discovery of astrophysical magnetic
fields, when George Ellery Hale recorded the Zeeman splitting of spectral lines
in sunspots. With the introduction of Babcock's photoelectric magnetograph it
soon became clear that the Sun's magnetic field outside sunspots is extremely
structured. The field strengths that were measured were found to get larger
when the spatial resolution was improved. It was therefore necessary to come up
with methods to go beyond the spatial resolution limit and diagnose the
intrinsic magnetic-field properties without dependence on the quality of the
telescope used. The line-ratio technique that was developed in the early 1970s
revealed a picture where most flux that we see in magnetograms originates in
highly bundled, kG fields with a tiny volume filling factor. This led to
interpretations in terms of discrete, strong-field magnetic flux tubes embedded
in a rather field-free medium, and a whole industry of flux tube models at
increasing levels of sophistication. This magnetic-field paradigm has now been
shattered with the advent of high-precision imaging polarimeters that allow us
to apply the so-called "Second Solar Spectrum" to diagnose aspects of solar
magnetism that have been hidden to Zeeman diagnostics. It is found that the
bulk of the photospheric volume is seething with intermediately strong, tangled
fields. In the new paradigm the field behaves like a fractal with a high degree
of self-similarity, spanning about 8 orders of magnitude in scale size, down to
scales of order 10 m.Comment: To appear in "Magnetic Coupling between the Interior and the
Atmosphere of the Sun", eds. S.S. Hasan and R.J. Rutten, Astrophysics and
Space Science Proceedings, Springer-Verlag, Heidelberg, Berlin, 200
Assessment of Climate Events in Changma Season (Korean Monsoon) for Production Trend of Sorghum-Sudangrass Hybrid (\u3ci\u3eSorghum bicolor\u3c/i\u3e L.) in the Central Inland Regions of Korea Using Time Series Analysis
This study aimed to assess the impact of climate events in the Changma (Korean Monsoon) season on the production trend of sorghum-sudangrass hybrid (SSH) in central inland regions using time series analysis. The dataset in Suwon from 1988–2013 (n = 388) was generated by merging SSH data and climate data. The accumulated temperature (SHAT, ℃), rainfall amount (SHRA, mm) and sunshine duration (SHSD, hr) from seeding to harvesting were used to assess their impact on the trend of dry matter yield (DMY, kg/ha) for SSH. Furthermore, heavy rainfall (HRF) and typhoons (TPH) were considered as climate events. As a result, the impact of climate events did not affect DMY, even though the frequency and intensity of HRF increased. Conversely, SHAT and SHRA had positive and negative effects on the trend of DMY, respectively. Therefore, the DMY trend of SSH was forecasted to increase until 2045, unlike maize, which has shown a declining trend. The forecasted DMY in 2045 was 14,926 kg/ha. It is likely that the damage by heavy rainfall and typhoons was reduced due to multiple-harvesting and a deeper extension of the root system. Therefore, in an environment that is rapidly changing due to climate change and abnormal weather, such as the Changma season, the cultivation of SSH would be advantageous as it would ensure a stable and robust yield
Assessment of Causality between Climate Variables and Production for Whole Crop Maize Using Structural Equation Modeling
This study aimed to assess the causality of different climate variables on the production of whole crop maize silage (Zea mays L.; WCM) in the central inland region of the Republic of Korea. Furthermore, the effect of these climate variables was also determined by looking at direct and indirect pathways during the stages before and after silking. The WCM metadata (n = 640) were collected from the Rural Development Administration’s reports of new variety adaptability from 1985‒2011 (27 years). The climate data was collected based on year and location from the Korean Meteorology Administration’s weather information system. Causality, in this study, was defined by various cause-and-effect relationships between climatic factors, such as temperature, rainfall amount, sunshine duration, wind speed and relative humidity in the seeding to silking stage and the silking to harvesting stage. All climate variables except wind speed were different before and after the silking stage, which indicates the silking occurred during the period when the Korean season changed from spring to summer. Therefore, the structure of causality was constructed by taking account of the climate variables that were divided by the silking stage. In particular, the indirect effect of rainfall through the appropriate temperature range was different before and after the silking stage. The damage caused by heat-humidity was having effect before the silking stage while the damage caused by night-heat was not affecting WCM production. There was a large variation in soil surface temperature and rainfall before and after the silking stage. Over 350 mm of rainfall affected dry matter yield (DMY) when soil surface temperatures were less than 22℃ before the silking stage. Over 900 mm of rainfall also affected DMY when soil surface temperatures were over 27℃ after the silking stage. For the longitudinal effects of soil surface temperature and rainfall amount, less than 22℃ soil surface temperature and over 300 mm of rainfall before the silking stage affected yield through over 26℃ soil surface temperature and less than 900 mm rainfall after the silking stage, respectively
Impact of Abnormal Climate Events on the Production of Italian Ryegrass as a Season in the Republic of Korea
This study aimed to assess the impact of abnormal climate events on the production of Italian ryegrass (IRG), such as autumn low-temperature, severe winter cold and spring droughts in the central inland, southern inland and southern coastal regions. Seasonal climatic variables, including temperature, precipitation, wind speed, relative humidity, and sunshine duration, were used to set the abnormal climate events using principal component analysis, and the abnormal climate events were distinguished from normal using Euclidean-distance cluster analysis. Furthermore, to estimate the impact caused by abnormal climate events, the dry matter yield (DMY) of IRG between abnormal and normal climate events was compared using a t-test with 5% significance level. As a result, the impact to the DMY of IRG by abnormal climate events in the central inland of Korea was significantly large in order of severe winter cold, spring drought, and autumn low temperature. In the southern inland regions, severe winter cold was also the most serious abnormal event. These results indicate that the severe cold is critical to IRG in inland regions. Meanwhile, in the southern coastal regions, where severe cold weather is rare, the spring drought was the most serious abnormal climate event. In particular, since 2005, the frequency of spring droughts has tended to increase. In consideration of the trend and frequency of spring drought events, it is likely that drought becomes a NEW NORMAL during spring in Korea. This study was carried out to assess the impact of seasonal abnormal climate events on the DMY of IRG, and it can be helpful to make a guideline for its vulnerability. This study was accepted in the Journal of Animal Science and Technology in 02/NOV/2020
Polarization Switching Dynamics Governed by Thermodynamic Nucleation Process in Ultrathin Ferroelectric Films
A long standing problem of domain switching process - how domains nucleate -
is examined in ultrathin ferroelectric films. We demonstrate that the large
depolarization fields in ultrathin films could significantly lower the
nucleation energy barrier (U*) to a level comparable to thermal energy (kBT),
resulting in power-law like polarization decay behaviors. The "Landauer's
paradox": U* is thermally insurmountable is not a critical issue in the
polarization switching of ultrathin ferroelectric films. We empirically find a
universal relation between the polarization decay behavior and U*/kBT.Comment: 5 pages, 4 figure
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