Observations of a Quickly Flapping Interplanetary Magnetic Reconnection Exhaust

On the basis of the Petschek reconnection model and the characteristics of reconnection, hundreds of reconnection exhausts were reported in the solar wind. Many multi-spacecraft observations also indicated that interplanetary magnetic reconnection is a quasi–steady-state plasma process and the reconnection X-line can extend hundreds of Earth radii. In this study, we report an interplanetary flapping reconnection exhaust observed by Wind on April 1, 2003 at one AU. The magnetic reconnection event has two adjacent accelerated flows. We compared the plasma and magnetic characteristics of the two accelerated flows and found that the second accelerated flow was due to the back-and-forth movement of the reconnection exhaust. Our observations reveal that not all interplanetary reconnections operate in a quasi–steady-state manner; some reconnection current sheets can move rapidly back and forth.

Reacciones y abordajes de las políticas educativas frente a los flujos migratorios: Una revisión en clave comparada de los casos de Chile y Cataluña

This article presents the results of a research study aimed to explore and analyze the configuration process and current situation of educational policies for foreign students in Chile and the Autonomous Community of Catalonia. From a qualitative approach, and based on a comparative documentary study, an integral vision of the scenario of policies and instruments of public action for the schooling of foreign students was built in both contexts. The results show more contrasts than similarities. Among the differences, the different configuration processes of these actions are highlighted, where the evolution of the migratory phenomenon and the characteristics of their political and educational systems influence. They also contrast the areas addressed by these actions and the ways in which inclusive education for foreign students is materialized. The most relevant similarity is the incorporation of inclusive education and intercultural education as central approaches of both educational systems and of the actions in favor of the schooling of these students. The value of the comparative study lies in the extensive and in-depth look at the development of educational policies and public action instruments to address the accelerated flow of migrants in school systems.

Use of computational fluid dynamics tools to calculate the dispersion of gas and aerosol emissions in conditions of a complex terrain

ANSYS FLUENT tools were used as part of a standard turbulence k-ε model to simulate the air flow around a number of typical obstacles (a solid cube, a solid hemisphere, and a 2D hill) which form a potential terrain in the NPP emission dispersion area and roughly correspond to the geometry of the buildings and structures within this area. For reproducibility, a non-uniform spatial grid is plotted in the computational region which condenses near the obstacle surface and the outer boundaries. The dimensions and the positions of the obstacles were chosen such that to ensure their best possible coincidence with the conditions of the published experiments. The result of simulating the velocity and direction of the air flow as the whole shows a good agreement with the data from the wind tunnel experiments in the areas in front of and over the obstacle, as well as in its air shadow. Typical accelerated flow, vortex, and reverse flow areas are reproduced reliably. There are variances observed only in the local heavy turbulence regions in the obstacle’s air shadow near the ground surface. All this indicates that it is possible to model in full scale the dispersion of the NPP emissions taking into account the peculiarities of the plant site terrain and the major onsite structures to determine more accurately the personnel and public exposure dose.

Theoretical Comparison of the Effects of Different Traffic Conditions on Urban Road Environmental External Costs

External costs that are associated with air pollution, climate change linked to greenhouse gas emissions (GHG), and noise are among the most important environmental externalities that are generated by road transport, which have been well monetized. This paper theoretically investigates the effects of different traffic conditions on the environmental external costs of urban roads where traffic flow is more complicated than un-interrupted traffic flows. A Monte Carlo method is used to theoretically simulate traffic speed in different traffic conditions. Subsequently, the emitted carbon dioxide (CO2), nitrogen oxides (NOx), carbon monoxide (CO), particulate matter (PM), sulfur dioxide (SO2), and noise were estimated in each of the theoretically simulated traffic conditions. Finally, the environmental external costs in each traffic condition were calculated taking the EU average costs values into account. The results showed that, when compared to free-flow condition, the total air pollutant and GHG external costs (€2010) have been increased by 6%, 31%, 44%, 50%, and 93% in under-saturated flow, accelerated flow, decelerated flow, congestion, and over-saturated congestion, respectively. Furthermore, the total noise cost (€2010/year/person exposed), as compared to free-flow condition, has been decreased by 2%, 11%, 12%, 36%, and 69% in accelerated flow, under-saturated flow, congestion, over-saturated congestion, and decelerated flow, respectively.

The architecture and evolution of shallow water delta mouth bars: examples from the Lower Cretaceous of Spain

<p>Improved understanding of delta mouth bar morphodynamics, and the resulting stratigraphic architectures, is important for predicting the loci of deposition of different sediment fractions, coastal geomorphic change and heterogeneity in mouth bar reservoirs. Facies and architectural analysis of exceptionally well-exposed shallow water (ca. 5 m depth) mouth bars and associated distributaries, from the Xert Formation (Lower Cretaceous), of the Maestrat Basin (east-central Spain), reveal that they grew via a succession of repeated autogenic cycles. The formation is part of a mixed clastic-carbonate succession deposited during a time of active faulting and incipient salt tectonism, but in an area away from their direct influence and where wave and tidal reworking were minimal.</p><p>An initial mouth bar accretion element forms after avulsion of a distributary into shallow standing water. Turbulent expansion of the fluvial jet and high bed friction results in rapid flow deceleration, and deposition of sediment in an aggradational to expansional bar-form. Vertical bar growth causes flattening and acceleration of the jet. The accelerated flow scours channels on the bar top, which focuses further expansion of the mouth bar at individual loci where the channels break through the front of the mouth bar. Here, new mouth bar accretion elements form, downlapping and onlapping against a readily recognizable surface of mouth bar reorganization. Vertical growth of the new mouth bar accretion elements causes flattening and re-acceleration of the jet, leading to channelization, and initiation of the next generation of mouth bar accretion elements. Thus the mouth bar grows, until bed-friction effects cause backwater deceleration and superelevation of flow in the feeding distributary. Within-channel sedimentation, choking and upstream avulsion of the feeding channel, results in mouth bar abandonment. In this study, mouth bars are formed of at least two to three accretion elements, before abandonment happened. The results of this study contrast with the notion that mouth bars form by simple vertical aggradation and radial expansion. However, the architecture and facies distributions of shallow water mouth bars are a predictable product of intrinsic processes that operate to deposit them.</p>