914 research outputs found
Waiting time distribution of solar energetic particle events modeled with a non-stationary Poisson process
We present a study of the waiting time distributions (WTDs) of solar
energetic particle (SEP) events observed with the spacecraft and .
Both the WTDs of solar electron events (SEEs) and solar proton events (SPEs)
display a power-law tail . The SEEs display a broken
power-law WTD. The power-law index is 0.99 for the short waiting
times (100
hours). The break of the WTD of SEEs is probably due to the modulation of the
corotating interaction regions (CIRs). The power-law index 1.82
is derived for the WTD of SPEs that is consistent with the WTD of type II radio
bursts, indicating a close relationship between the shock wave and the
production of energetic protons. The WTDs of SEP events can be modeled with a
non-stationary Poisson process which was proposed to understand the waiting
time statistics of solar flares (Wheatland 2000; Aschwanden McTiernan
2010). We generalize the method and find that, if the SEP event rate varies as the time distribution of event rate , the time-dependent Poisson distribution
can produce a power-law tail WTD , where .Comment: 10 pages, 4 figures, accepted for publication in ApJ Letter
Impact of information cost and switching of trading strategies in an artificial stock market
This paper studies the switching of trading strategies and its effect on the
market volatility in a continuous double auction market. We describe the
behavior when some uninformed agents, who we call switchers, decide whether or
not to pay for information before they trade. By paying for the information
they behave as informed traders. First we verify that our model is able to
reproduce some of the stylized facts in real financial markets. Next we
consider the relationship between switching and the market volatility under
different structures of investors. We find that there exists a positive
relationship between the market volatility and the percentage of switchers. We
therefore conclude that the switchers are a destabilizing factor in the market.
However, for a given fixed percentage of switchers, the proportion of switchers
that decide to buy information at a given moment of time is negatively related
to the current market volatility. In other words, if more agents pay for
information to know the fundamental value at some time, the market volatility
will be lower. This is because the market price is closer to the fundamental
value due to information diffusion between switchers.Comment: 15 pages, 9 figures, Physica A, 201
Physical outdoor activity versus indoor activity: their influence on environmental behaviors
There are strong evidences linking physical outdoor activity and health benefits; however, little is known about the impact on environmental behaviors. Thus, this study aims to close this gap by investigating the influence of physical outdoor activity on environmental behaviors. A total of 416 surveys were distributed to students in eight public primary schools located near the Hsinchu Science and Industrial Park in Taiwan. Findings from the analysis revealed that subjective norms had a more influential effect on environmental behaviors for participants who engaged in physical activity at outdoor parks. In contrast, descriptive norms had a direct predictive impact on environmental behaviors for participants whose main physical activity venue was at the indoor after-school
centers. Research results also highlighted attitude as the strongest predictive variable influence on environmental behaviors for children who engaged in physical indoor and outdoor activities
Structure-Exploiting Delay-Dependent Stability Analysis Applied to Power System Load Frequency Control
Linear matrix inequality (LMI) based delay-dependent stability analysis/synthesis methods have been applied to power system load frequency control (LFC) which has communication networks in its loops. However, the computational burden of solving large-scale LMIs poses a great challenge to the application of those methods to real-world power systems. This paper investigates the computational aspect of delay-dependent stability analysis (DDSA) of LFC. The basic idea is to improve the numerical tractability of DDSA by exploiting the chordal sparsity and symmetry of the graph related to LFC loops. The graph-theoretic analysis yields the structure restrictions of weighting matrices needed for the LMIs to inherit the chordal sparsity of the control loops. By enforcing those structure restrictions on weighting matrices, the positive semidefinite constraints in the LMIs can be decomposed into smaller ones, and the number of decision variables can be greatly reduced. Symmetry in LFC control loops is also exploited to reduce the number of decision variables. Numerical studies show the proposed structure-exploiting techniques significantly improves the numerical tractability of DDSA at the cost of the introduction of acceptable minor conservatism
BGO quenching effect on spectral measurements of cosmic-ray nuclei in DAMPE experiment
The Dark Matter Particle Explorer (DAMPE) is a satellite-borne detector
designed to measure high energy cosmic-rays and -rays. As a key
sub-detector of DAMPE, the Bismuth Germanium Oxide (BGO) imaging calorimeter is
utilized to measure the particle energy with a high resolution. The nonlinear
fluorescence response of BGO for large ionization energy deposition, known as
the quenching effect, results in an under-estimate of the energy measurement
for cosmic-ray nuclei. In this paper, various models are employed to
characterize the BGO quenching factors obtained from the experimental data of
DAMPE. Applying the proper quenching model in the detector simulation process,
we investigate the tuned energy responses for various nuclei and compare the
results based on two different simulation softwares, i.e. GEANT4 and FLUKA. The
BGO quenching effect results in a decrease of the measured energy by
approximately () for carbon (iron) at 10 GeV/n and
above 1 TeV/n, respectively. Accordingly, the correction of the BGO quenching
effect leads to an increase of the low-energy flux measurement of cosmic-ray
nuclei.Comment: 13 pages, 4 figures, to be published in Nuclear Inst. and Methods in
Physics Research,
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Selection and environmental adaptation along a path to speciation in the Tibetan frog Nanorana parkeri.
Tibetan frogs, Nanorana parkeri, are differentiated genetically but not morphologically along geographical and elevational gradients in a challenging environment, presenting a unique opportunity to investigate processes leading to speciation. Analyses of whole genomes of 63 frogs reveal population structuring and historical demography, characterized by highly restricted gene flow in a narrow geographic zone lying between matrilines West (W) and East (E). A population found only along a single tributary of the Yalu Zangbu River has the mitogenome only of E, whereas nuclear genes of W comprise 89-95% of the nuclear genome. Selection accounts for 579 broadly scattered, highly divergent regions (HDRs) of the genome, which involve 365 genes. These genes fall into 51 gene ontology (GO) functional classes, 14 of which are likely to be important in driving reproductive isolation. GO enrichment analyses of E reveal many overrepresented functional categories associated with adaptation to high elevations, including blood circulation, response to hypoxia, and UV radiation. Four genes, including DNAJC8 in the brain, TNNC1 and ADORA1 in the heart, and LAMB3 in the lung, differ in levels of expression between low- and high-elevation populations. High-altitude adaptation plays an important role in maintaining and driving continuing divergence and reproductive isolation. Use of total genomes enabled recognition of selection and adaptation in and between populations, as well as documentation of evolution along a stepped cline toward speciation
Determinants of pro-environmental behavior among excessive smartphone usage children and moderate smartphone usage children in Taiwan
Introduction Although there is evidence linking the relationships between smartphone usage with health, stress, and academic performance, there is still inadequate knowledge about the influence on pro-environmental behaviors. This study seeks to bridge this gap by adapting the theory of attribution framework to examine the effects of personal norms, social norms, perceived behavioral control on pro-environmental behavior of smartphone usage in children. Methods A total of 225 children aged between 11 to 12 from eight selected public primary schools at the Hsinchu Science and Industrial Park in Taiwan were surveyed. Two distinct groups (excessive versus moderate usage) were purposefully selected for comparison, of which 96 participants were excessive smartphone users while the remaining 129 were moderate smartphone users. Results Findings revealed significant differences between excessive and moderate smartphone usage children groups in personal norms (p  0.05), as well as social norms and pro-environmental behavior for moderate smartphone usage children (β = 0.181, t = 1.924, p > 0.05), but such a relationship could be developed through the mediating effect of perceived behavioral control (β = 0.497, t = 4.471***, p < 0.001). Discussion The results suggested that excessive smartphone usage children lack positive perceived behavioral control, and their pro-environmental behavior could only be predicted through explicit social norms, whereas pro-environmental behavior of moderate smartphone usage children was implicitly influenced by personal norms through perceived behavioral control
Two-fold symmetric superconductivity in the kagome superconductor RbV3Sb5
The recent discovered kagome superconductors provide a good platform for
studying intertwined orders and novel states such as topology, superconductor,
charge density wave, et al. The interplay of these orders may spontaneously
break the rotational symmetry, and induce exotic phenomena such as nematicity,
or even nematic superconductor. Here we report a two-fold rotational symmetric
superconductivity of thin-film RbV3Sb5 in response to a direction-dependent
in-plane magnetic fields, in contrast to the six-fold structural symmetry of
the crystal lattice. The two-fold symmetry was evidenced by the
magnetoresistance transport experiments, critical magnetic field measurements
and the anisotropic superconducting gap. With different configuration, we
further observed the six-fold symmetry superimposed on the two-fold symmetry
near the boundary between normal states and superconducting states. Our results
present the correlation-driven symmetry breaking and highlight the promising
platform to study the intertwined orders such as unconventional
superconductivity in this correlated kagome family
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