Exploring non-adiabatic approximations to the exchange-correlation functional of TDDFT

A decomposition of the exact exchange-correlation potential of time-dependent density functional theory into an interaction component and a kinetic component offers a new starting point for non-adiabatic approximations. The components are expressed in terms of the exchange-correlation hole and the difference between the one-body density matrix of the interacting and Kohn-Sham systems, which must be approximated in terms of quantities accessible from the Kohn-Sham evolution. We explore several preliminary approximations, evaluate their fulfillment of known exact conditions, and test their performance on simple model systems for which available exact solutions indicate the significance of going beyond the adiabatic approximation.Fil: Fuks, Johanna Ildemar. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Lacombe, Lionel. University of New York; Estados UnidosFil: Nielsen, Søren E. B.. Max Planck Institute for the Structure and Dynamics of Matter; Alemania. Center for Free-Electron Laser Science; AlemaniaFil: Maitra, Neepa T.. University of New York; Estados Unido

Phase Stability and Segregation in Alloy 22 Base Metal and Weldments

The current design of the waste disposal containers relies heavily on encasement in a multi-layered container, featuring a corrosion barrier of Alloy 22, a Ni-Cr-Mo-W based alloy with excellent corrosion resistance over a wide range of conditions. The fundamental concern from the perspective of the Yucca Mountain Project, however, is the inherent uncertainty in the (very) long-term stability of the base metal and welds. Should the properties of the selected materials change over the long service life of the waste packages, it is conceivable that the desired performance characteristics (such as corrosion reistance) will become compromised, leading to premature failure of the system. To address this, we will study the phase stability and solute segregation characteristics of Alloy 22 base metal and welds. A better understanding of the underlying microstructural evolution tendencies, and their connections with corrosion behavior will (in turn) produce a higher confidence in the extrapolated behavior of the container materials over time periods that are not feasibly tested in a laboratory. Additionally, the knowledge gained here may potentially lead to cost savings through development of safe and realistic design constraints and model assumptions throughout the entire disposal system

First NACO observations of the Brown Dwarf LHS 2397aB

Observations of the standard late type M8 star LHS 2397aA were obtained at the ESO-VLT 8m telescope ``Yepun'' using the NAOS/CONICA Adaptive Optics facility. The observations were taken during the NACO commissioning, and the infrared standard star LHS 2397aA was observed in the H, and Ks broad band filters. In both bands the brown dwarf companion LHS2397aB was detected. Using a program recently developed (Bouy et al., 2003) for the detection of stellar binaries we calculated the principal astrometric parameters (angular binary separation and position angle P.A.) and the photometry of LHS 2397aA and LHS 2397aB. Our study largely confirms previous results obtained with the AO-Hokupa'a facility at Gemini-North (Freed et al., 2003); however a few discrepancies are observed.Comment: 5 page

A simple model for the microscopic effective pairing interaction

The microscopic effective pairing interaction in the $^1S_0$-channel is investigated for two different values of the chemical potential $\mu$ starting from the separable form of the Paris NN-potential. It is shown that, within a high accuracy, this effective interaction can be approximated by the off-shell free T-matrix taken at the negative energy $E=2\mu$.Comment: LaTeX, 8 pages, 6 ps-figure

Technologies, markets and challenges for development of the Canadian Oil Sands industry

This paper provides an overview of the current status of development of the Canadian oil sands industry, and considers possible paths of further development. We outline the key technology alternatives, critical resource inputs and environmental challenges and strategic options both at the company and government level. We develop a model to calculate the supply cost of bitumen and synthetic crude oil using the key technologies. Using the model we evaluate the sensitivity of the supply costs to the critical model inputs

Is Turing's Thesis the Consequence of a More General Physical Principle?

We discuss historical attempts to formulate a physical hypothesis from which Turing's thesis may be derived, and also discuss some related attempts to establish the computability of mathematical models in physics. We show that these attempts are all related to a single, unified hypothesis.Comment: 10 pages, 0 figures; section 1 revised, other minor change

Surface behaviour of the pairing gap in semi-infinite nuclear matter

The $^1S_0$-pairing gap in semi-infinite nuclear matter is evaluated microscopically using the effective pairing interaction recently found explicitly in the coordinate representation starting from the separable form of the Paris NN-potential. Instead of direct iterative solution of the gap equation, a new method proposed by V.A.Khodel, V.V.Khodel and J.W.Clark was used which simplifies the procedure significantly. The gap $\Delta$ obtained in our calculations exibits a strong variation in the surface region with a pronounced maximum near the surface.Comment: 9 pages, 2 ps figure

3D SIMULATION OF A 500KG UO2 MELT IN A COLD CRUCIBLE INDUCTION FURNACE

International audienc

Les modèles numériques des microhabitats des passons : application et nouveaux développements

L'estimation des stocks de poissons que peut abriter un secteur de cours d'eau non pollué nécessite le calcul de sa capacité d'accueil en terme d'espace et de nourriture. Le premier volet a donné lieu aux Etats-Unis à la mise en place de modèles de comportement de différentes espèces de poissons en fonction de variables physiques et de modèles hydrauliques décrivant l'évolution temporelle de ces variables.Les hypothèses sous-jacentes sont discutées. Une modification du calcul de la perte de charge linéaire est préconisée pour le modèle hydraulique dans le cas des rivières à truites, et l'utilisation de méthodes multivariées est proposée pour décrire avec une meilleure fiabilité les relations entre densités de poissons et variables physiques des cours d'eau.Quelques cas d'application illustrent l'intérêt de cette démarche pour répondre à des questions posées par les gestionnaires, tant en matière de prévision des impacts piscicoles des aménagements que d'optimisation des repeuplements.When evaluating the potential fish stock that an unpolluted reach of a stream can accomodate, the load capacity with regard to space and food available must be assessed. It is for this purpose that the Instream Flow Incremental Methodology has been developed in the United States.The assumptions on which behavioural and hydraulic models are based are discussed and modifications are suggested to improve the efficiency of this methodology.The use of the Manning equation to compute the energy loss is misleading in the case of trout streams and results from simulation are more reliable when using resistance equations designed for mountain rivers.For biological monitoring, multivariate data analysis is an interesting alternative to drawing one-dimensional preference curves. Qualitative variables can be used and redundancy or dependence between parameters no longer distorts the results. The relations between physical variables of streams and a probability of the presence of fish are estimated with greater accuracy.Examples of the application of this methodology are presented with a view to assessing the effects of water abstraction on fish populations and to optimizing the restocking of trout streams

Numerical simulations in the development of the French radioactive waste vitrification processes using induction furnace

International audienceFor many years, the CEA (Commissariat à l’Énergie Atomique et aux Énergies Alternatives) Marcoule France has developed various processes dedicated to radioactive waste confinement, especially vitrification processes for HLLW. For 15 years now, the numerical simulation has become an important tool for research and developement projects held in the CEA-AREVA Joint Vitrification Laboratory (LCV). Induction heating, fluid mechanics and thermal simulations take part of all new R&D projects. The apports of such simulations are, first, the enhancement of the working knowledge of existing process. Those data are very useful to define optimisation choices, for example upgrades made on the hot metallic melter used since the 90s at LaHague facility. Second, the simulations are, of course, also used at the conception stage of new processes as a tool allowing wide ranges parametric tests. This has been extensively used in the design of the cold crucible inductive melter (CCIM) commissioned in 2010 at La Hague plant. Finally, it is a powerful and relatively cheap tool for prospective studies for processes of the future. Whatever the purpose, the potential benefits are gains on the reliability, the output capacity and the life time