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 $X$ having all cycles in \A, and by dw(\A) the class of complexes $Y$ with all components $Y_j$ in \A. We consider a two sided noetherian ring $R$ and we use the notations $\mathcal{GI}$ $(\mathcal{GF}, \mathcal{GP})$ for the class of Gorenstein injective (flat, projective respectively) $R$-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 $\widetilde{\mathcal{GI}}$. 3. Every complex in $dw(\mathcal{GI})$ 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 $R$, 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 $R$ with a dualizing complex, the class of exact complexes of injectives coincides with that of totally acyclic complexes of injectives if and only if $R$ 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 $R$ that also has finite finitistic flat dimension, every complex of injective (left and respectively right) $R$-modules is totally acyclic if and only if $R$ is a Gorenstein ring