The Role of Bound States in Time-Dependent Quantum Transport

Charge transport through a nanoscale junction coupled to two macroscopic electrodes is investigated for the situation when bound states are present. We provide numerical evidence that bound states give rise to persistent, non-decaying current oscillations in the junction. We also show that the amplitude of these oscillations can exhibit a strong dependence on the history of the applied potential as well as on the initial equilibrium configuration. Our simulations allow for a quantitative investigation of several transient features. We also discuss the existence of different time-scales and address their microscopic origin.Comment: 10 pages, 8 figure

Evolving and sustaining ocean best practices and standards for the next decade

The oceans play a key role in global issues such as climate change, food security, and human health. Given their vast dimensions and internal complexity, efficient monitoring and predicting of the planet's ocean must be a collaborative effort of both regional and global scale. A first and foremost requirement for such collaborative ocean observing is the need to follow well-defined and reproducible methods across activities: from strategies for structuring observing systems, sensor deployment and usage, and the generation of data and information products, to ethical and governance aspects when executing ocean observing. To meet the urgent, planet-wide challenges we face, methods across all aspects of ocean observing should be broadly adopted by the ocean community and, where appropriate, should evolve into "Ocean Best Practices." While many groups have created best practices, they are scattered across the Web or buried in local repositories and many have yet to be digitized. To reduce this fragmentation, we introduce a new open access, permanent, digital repository of best practices documentation (oceanbestpractices.org) that is part of the Ocean Best Practices System (OBPS). The new OBPS provides an opportunity space for the centralized and coordinated improvement of ocean observing methods. The OBPS repository employs user-friendly software to significantly improve discovery and access to methods. The software includes advanced semantic technologies for search capabilities to enhance repository operations. In addition to the repository, the OBPS also includes a peer reviewed journal research topic, a forum for community discussion and a training activity for use of best practices. Together, these components serve to realize a core objective of the OBPS, which is to enable the ocean community to create superior methods for every activity in ocean observing from research to operations to applications that are agreed upon and broadly adopted across communities. Using selected ocean observing examples, we show how the OBPS supports this objective. This paper lays out a future vision of ocean best practices and how OBPS will contribute to improving ocean observing in the decade to come

Damage and fracture in superplastic alloys - a current state of art

International audienceMany superplastic alloys are sensitive to strain induced cavitation. A specificity of damage in superplastic conditions comes from the importance of grain boundary sliding (GBS) which induces generally a significant role of cavity coalescence compared to the conventional steps of nucleation and cavity growth. In terms of cavity morphologies, the GBS contribution promotes the development of cavities with particularly complex shapes. A way to limit damage sensitivity can be to reduce the grain size in the superplastic alloy since it is expected to decrease the associated flow stress and consequently the cavity nucleation rate during deformation. Nevertheless, for ultra fine grained microstructures (like those obtained after severe plastic deformation techniques), superplastic properties can frequently be obtained at lower temperatures than for more conventional microstructures. In such cases, the effect on cavitation may be not straightforward and may depend on applied conditions. The aim of this presentation is to give a brief review of the state of art concerning recent studies of damage in superplastic alloys and to discuss about the benefits and/or drawbacks of grain refining on the associated damage mechanisms

Forming of bulk metallic glasses: ideal superplasticity?

International audienceDue to their brittleness, bulk metallic glasses (BMG) are generally difficult to form at room temperature. A fruitful way to get components is to deform them in their supercooled liquid region (SLR). In this region, BMG generally exhibit particularly large strain capacities. This behaviour is sometimes reported as superplasticity since several requirements of superplasticity are fulfilled. For instance, particularly large m values (up to 1) can be measured and consequently one can wonder if such forming conditions of BMG can be considered as ideal superplasticity. In this paper, we report studies dealing with high temperature deformation of various BMGs. Similarities and differences between high temperature deformation of BMGs and superplasticity of fine grained alloys are discussed

Effect of temperature on deformability of magnesium alloys: plastic stability and damage sensitivity

International audienc

Large plastic stability in magnesium alloys:crystalline vs. amorphous alloys

International audienc

The process of equal channel angular extrusion

Very fine grains can be obtained in metallic alloys by severe plastic deformation. Equal Channel Angular Extrusion (ECAE) is a convenient way to apply large strains by simple shear. A billet is punched through two channels of equal cross-section intersecting at a given angle. The operation can be repeated several times since the shape of the billet remains the same after each pass. Submicrometer-grained materials can be produced by multiple extrusions

Damage development during superplasticity of light alloys

International audienc