1,190 research outputs found
Three-dimensional Magnetic Restructuring in Two Homologous Solar Flares in the Seismically Active NOAA AR 11283
We carry out a comprehensive investigation comparing the three-dimensional
magnetic field restructuring, flare energy release, and the helioseismic
response, of two homologous flares, the 2011 September 6 X2.1 (FL1) and
September 7 X1.8 (FL2) flares in NOAA AR 11283. In our analysis, (1) a twisted
flux rope (FR) collapses onto the surface at a speed of 1.5 km/s after a
partial eruption in FL1. The FR then gradually grows to reach a higher altitude
and collapses again at 3 km/s after a fuller eruption in FL2. Also, FL2 shows a
larger decrease of the flux-weighted centroid separation of opposite magnetic
polarities and a greater change of the horizontal field on the surface. These
imply a more violent coronal implosion with corresponding more intense surface
signatures in FL2. (2) The FR is inclined northward, and together with the
ambient fields, it undergoes a southward turning after both events. This agrees
with the asymmetric decay of the penumbra observed in the peripheral regions.
(3) The amounts of free magnetic energy and nonthermal electron energy released
during FL1 are comparable to those of FL2 within the uncertainties of the
measurements. (4) No sunquake was detected in FL1; in contrast, FL2 produced
two seismic emission sources S1 and S2 both lying in the penumbral regions.
Interestingly, S1 and S2 are connected by magnetic loops, and the stronger
source S2 has weaker vertical magnetic field. We discuss these results in
relation to the implosion process in the low corona and the sunquake
generation.Comment: 12 pages, 9 figures, accepted to the Astrophysical Journa
Optimizing city-scale traffic through modeling observations of vehicle movements
The capability of traffic-information systems to sense the movement of
millions of users and offer trip plans through mobile phones has enabled a new
way of optimizing city traffic dynamics, turning transportation big data into
insights and actions in a closed-loop and evaluating this approach in the real
world. Existing research has applied dynamic Bayesian networks and deep neural
networks to make traffic predictions from floating car data, utilized dynamic
programming and simulation approaches to identify how people normally travel
with dynamic traffic assignment for policy research, and introduced Markov
decision processes and reinforcement learning to optimally control traffic
signals. However, none of these works utilized floating car data to suggest
departure times and route choices in order to optimize city traffic dynamics.
In this paper, we present a study showing that floating car data can lead to
lower average trip time, higher on-time arrival ratio, and higher
Charypar-Nagel score compared with how people normally travel. The study is
based on optimizing a partially observable discrete-time decision process and
is evaluated in one synthesized scenario, one partly synthesized scenario, and
three real-world scenarios. This study points to the potential of a "living
lab" approach where we learn, predict, and optimize behaviors in the real
world
Symmetry Protected Josephson Supercurrents in Three-Dimensional Topological Insulators
Coupling the surface state of a topological insulator (TI) to an s-wave
superconductor is predicted to produce the long-sought Majorana quasiparticle
excitations. However, superconductivity has not been measured in surface states
when the bulk charge carriers are fully depleted, i.e., in the true topological
regime that is relevant for investigating Majorana modes. Here, we report
measurements of DC Josephson effects in TI-superconductor junctions as the
chemical potential is moved from the bulk bands into the band gap, or through
the true topological regime characterized by the presence of only surface
currents. We examine the relative behavior of the system at different
bulk/surface ratios, determining the effects of strong bulk/surface mixing,
disorder, and magnetic field. We compare our results to 3D quantum transport
simulations to conclude that the supercurrent is largely carried by surface
states, due to the inherent topology of the bands, and that it is robust
against disorder
Transformational Leadership in Operational Competitiveness Improvement: A Case Study in Malaysian Automotive Industry
The purpose of this paper is to analyze operational competitiveness by two core factors, i.e. manufacturing strategy and transformational leadership with technology level. In additional, CFI models in sense and respond (S&R) method are introduced to optimize strategic adjustments, which give supports in fast strategic decision-making process. The analysis results of case study show that leaders in automobile companies in Malaysia should deeply develop their leadership by inspirational motivation, intellectual stimulation and building trust and confidence etc. to improve operational competitiveness. Agile operations strategy should be utilized towards automobile enterprises in Malaysia in order to be competitive under dynamic and tightrope business situations.© 2012 The authors. Published under the terms of the Creative Commons Attribution-Non-Commercial-NoDerivs license (http://creativecommons.org/licenses/by-nc-nd/3.0/).fi=vertaisarvioitu|en=peerReviewed
Totally acyclic complexes
For a given class of modules \A, we denote by \widetilde{\A} the class of
exact complexes having all cycles in \A, and by dw(\A) the class of
complexes with all components in \A. We consider a two sided
noetherian ring and we use the notations for the class of Gorenstein injective (flat, projective
respectively) -modules. We prove (Theorem 1) that the following are
equivalent: 1. Every exact complex of injective modules is totally acyclic. 2.
Every exact complex of Gorenstein injective modules is in
. 3. Every complex in is
dg-Gorenstein injective. Theorem 2 shows that the analogue result for complexes
of flat and Gorenstein flat modules also holds. We prove (Corollary 1) that,
over a commutative noetherian ring , the equivalent statements in Theorem 1
(as well as their counterparts from Theorem 2) hold if and only if the ring is
Gorenstein. Thus we improve on a result of Iyengar's and Krause's; in [18] they
proved that for a commutative noetherian ring with a dualizing complex, the
class of exact complexes of injectives coincides with that of totally acyclic
complexes of injectives if and only if is Gorenstein. We are able to remove
the dualizing complex hypothesis. In the second part of the paper we focus on
two sided noetherian rings that satisfy the Auslander condition. We prove
(Theorem 6) that for such a ring that also has finite finitistic flat
dimension, every complex of injective (left and respectively right) -modules
is totally acyclic if and only if is a Gorenstein ring
- …