20,729 research outputs found
On the inward drift of runaway electrons during the plateau phase of runaway current
The well observed inward drift of current carrying runaway electrons during
runaway plateau regime after disruption is studied by considering the phase
space dynamic of runaways in a large aspect ratio toroidal system. We consider
the case where the toroidal field is unperturbed and the toroidal symmetry of
the system is preserved. The balance between the change in canonical angular
momentum and the input of mechanical angular momentum in such system requires
runaways to drift horizontally in configuration space for any given change in
momentum space. The dynamic of this drift can be obtained by taking the
variation of canonical angular momentum. It is then found that runaway
electrons will always drift inward as long as they are decelerating. This drift
motion is essentially non-linear, since the current is carried by runaways
themselves, and any runaway drift relative to the magnetic axis will cause
further displacement of the axis itself. A simplified analytical model is
constructed to describe such inward drift both in ideal wall case and no wall
case, and the runaway current center displacement as a function of parallel
momentum variation is obtained. The time scale of such displacement is
estimated by considering effective radiation drag, which shows reasonable
agreement with observed displacement time scale. This indicates that the phase
space dynamic studied here plays a major role in the horizontal displacement of
runaway electrons during plateau regime.Comment: 25 pages, 9 figures, submitted to Physics of Plasma
An Empirical Study on Continuance Using Intention of Mobile Social Apps
User’s continuance intention is vital to the future of mobile social apps (i.e. applications) with rapid development and intensive competitions among their providers. We draw on the theory of flow experience and switching cost to build an integrated model to explain factors influencing users’ continuance using intention. Our model is tested by survey and Structural Equation Model (SEM) in the mobile social apps context of Wechat because of its popularity. The empirical results show that: Perceived enjoyment has significant influence on flow experience, and further positively affect users’ continuance using intention; Switching costs exert significant positive effect on continuance intention; Contrary to our hypothesis, time flexibility of mobile devices has no significant influence on users’ continuance using intention towards mobile social apps. With regard to the mediating effect of flow experience, we find that it exerts partially mediating effect between perceived enjoyment and continuance using intention and exert no mediating effect between mobile time flexibility and users’ continuance using intention towards mobile social apps
Optical Monitoring of the Seyfert Galaxy NGC 4151 and Possible Periodicities in the Historical Light Curve
We report B, V, and R band CCD photometry of the Seyfert galaxy NGC 4151
obtained with the 1.0-m telescope at Weihai Observatory of Shandong University
and the 1.56-m telescope at Shanghai Astronomical Observatory from 2005
December to 2013 February. Combining all available data from literature, we
have constructed a historical light curve from 1910 to 2013 to study the
periodicity of the source using three different methods (the Jurkevich method,
the Lomb-Scargle periodogram method and the Discrete Correlation Function
method). We find possible periods of P_1=4\pm0.1, P_2=7.5\pm0.3 and
P_3=15.9\pm0.3 yr.Comment: 8 pages, 5 figures, Accepted by Research in Astronomy and
Astrophysic
Study on space-time structure of Higgs boson decay using HBT correlation Method in ee collision at =250 GeV
The space-time structure of the Higgs boson decay are carefully studied with
the HBT correlation method using ee collision events produced through
Monte Carlo generator PYTHIA 8.2 at =250GeV. The Higgs boson jets
(Higgs-jets) are identified by H-tag tracing. The measurement of the Higgs
boson radius and decay lifetime are derived from HBT correlation of its decay
final state pions inside Higgs-jets in the ee collisions events with an
upper bound of fm and fs. This result is consistent with CMS data.Comment: 7 pages,3 figure
Straight-line Drawability of a Planar Graph Plus an Edge
We investigate straight-line drawings of topological graphs that consist of a
planar graph plus one edge, also called almost-planar graphs. We present a
characterization of such graphs that admit a straight-line drawing. The
characterization enables a linear-time testing algorithm to determine whether
an almost-planar graph admits a straight-line drawing, and a linear-time
drawing algorithm that constructs such a drawing, if it exists. We also show
that some almost-planar graphs require exponential area for a straight-line
drawing
Effects of past and current crop management on leaching losses, soil microbial community composition and activity
A lysimeter experiment was conducted to investigate the effect of past and current management practices on soil microbial biomass, activity and community composition. Intact monolith lysimeters were taken from sites of the same soil type that had been under long-term organic and conventional crop management. They were subjected to the same crop rotation and managed according to best organic and conventional practices. Mineral N loss was determined in leachates and soil samples taken before the experiment and after 30 months were analysed for biological soil properties, including microbial diversity. Results indicated that leaching losses were similar for all treatments and that crop was the main influence on microbial biomass composition and size, while microbial activity was determined by management history
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