5,197 research outputs found
On the ground states and dynamics of space fractional nonlinear Schr\"{o}dinger/Gross-Pitaevskii equations with rotation term and nonlocal nonlinear interactions
In this paper, we propose some efficient and robust numerical methods to
compute the ground states and dynamics of Fractional Schr\"{o}dinger Equation
(FSE) with a rotation term and nonlocal nonlinear interactions. In particular,
a newly developed Gaussian-sum (GauSum) solver is used for the nonlocal
interaction evaluation \cite{EMZ2015}. To compute the ground states, we
integrate the preconditioned Krylov subspace pseudo-spectral method \cite{AD1}
and the GauSum solver. For the dynamics simulation, using the rotating
Lagrangian coordinates transform \cite{BMTZ2013}, we first reformulate the FSE
into a new equation without rotation. Then, a time-splitting pseudo-spectral
scheme incorporated with the GauSum solver is proposed to simulate the new FSE
Physics of Extremely High Energy Cosmic Rays
Over the last third of the century, a few tens of events, detected by
ground-based cosmic ray detectors, have opened a new window in the field of
high-energy astrophysics. These events have macroscopic energies, unobserved
sources, an unknown chemical composition and a production and transport
mechanism yet to be explained. With a flux as low as one particle per century
per square kilometer, only dedicated detectors with huge apertures can bring in
the high-quality and statistically significant data needed to answer those
questions. In this article, we review the present status of the field both from
an experimental and theoretical point of view. Special attention is given to
the next generation of detectors devoted to the thorough exploration of the
highest energy rangesComment: 43 pages, 12 figures, submitted to International Journal of Modern
Physics
Bank liquidity, interbank markets and monetary policy
A major lesson of the recent financial crisis is that the interbank lending market is crucial for banks facing large uncertainty regarding their liquidity needs. This paper studies the efficiency of the interbank lending market in allocating funds. We consider two different types of liquidity shocks leading to different implications for optimal policy by the central bank. We show that, when confronted with a distributional liquidity-shock crisis that causes a large disparity in the liquidity held among banks, the central bank should lower the interbank rate. This view implies that the traditional tenet prescribing the separation between prudential regulation and monetary policy should be abandoned. In addition, we show that, during an aggregate liquidity crisis, central banks should manage the aggregate volume of liquidity. Two different instruments, interest rates and liquidity injection, are therefore required to cope with the two different types of liquidity shocks. Finally, we show that failure to cut interest rates during a crisis erodes financial stability by increasing the risk of bank runs.Bank liquidity, interbank markets, central bank policy, financial fragility, bank runs.
Grand Challenge of Psychopathology in the Years to Come
SCOPUS: no.jinfo:eu-repo/semantics/publishe
Control Strategies for Open-End Winding Drives Operating in the Flux-Weakening Region
This paper presents and compares control strategies for three-phase open-end winding drives operating in the flux-weakening region. A six-leg inverter with a single dc-link is associated with the machine in order to use a single energy source. With this topology, the zero-sequence circuit has to be considered since the zero-sequence current can circulate in the windings. Therefore, conventional over-modulation strategies are not appropriate when the machine enters in the flux-weakening region. A few solutions dealing with the zero-sequence circuit have been proposed in literature. They use a modified space vector modulation or a conventional modulation with additional voltage limitations. The paper describes the aforementioned strategies and then a new strategy is proposed. This new strategy takes into account the magnitudes and phase angles of the voltage harmonic components. This yields better voltage utilization in the dq frame. Furthermore, inverter saturation is avoided in the zero-sequence frame and therefore zero-sequence current control is maintained. Three methods are implemented on a test bed composed of a three-phase permanent-magnet synchronous machine, a six-leg inverter and a hybrid DSP/FPGA controller. Experimental results are presented and compared for all strategies. A performance analysis is conducted as regards the region of operation and the machine parameters.Projet SOFRACI/FU
Modeling and computation of Bose-Einstein condensates: stationary states, nucleation, dynamics, stochasticity
International audienceThe aim of this chapter is first to give an introduction to the derivation of the Gross-Pitaevskii Equations (GPEs) that arise in the modeling of Bose-Einstein Condensates (BECs). In particular, we describe some physical problems related to stationary states, dynamics, multi-components BECs and the possibility of handling stochastic effects into the equation. Next, we explain how to compute the stationary (and ground) states of the GPEs through the imaginary time method (also called Conjugate Normalized Gradient Flow) and finite difference or pseudo-spectral dis-cretization techniques. Examples are provided by using GPELab which is a Mat-lab toolbox dedicated to the numerical solution of GPEs. Finally, we explain how to discretize correctly the time-dependent GPE so that the schemes are physically admissible. We again provide some examples by using GPELab. Furthermore, extensions of the discretization schemes to some classes of stochastic (in time) GPEs are described and analyzed
Les espaces publics dans les territoires de densités intermédiaires : conceptions, usages et potentialités
National audiencePublic spaces in periurban areas often have a poor image. They are considered either as insufficiently developed, or as emblematic of privatised town development. To overcome this simplistic vision, and in order to understand the specificity of these areas, this article seeks to distance itself both from a “periurban” reading of these areas and from an “urban-centred” view of public spaces. Based on a survey conducted in the northern outskirts of the Paris region, it highlights the design logic of public authorities, as well as the convergences and discrepancies with the inhabitants’ behaviour. Finally it puts forward some possibilities for action.Souvent perçus négativement, les espaces publics périurbains sont considérés soit comme insuffisamment développés, soit comme emblématiques de la ville privatisée. Pour sortir de cette vision réductrice et en saisir la spécificité, cet article entend prendre ses distances par rapport à une lecture « péri-urbaine » de ces territoires et à une lecture « urbano-centrée » des espaces publics. À partir d’une enquête menée sur les franges nord de l’agglomération parisienne, elle met en évidence les logiques de conception véhiculées par les pouvoirs publics, les convergences et les décalages avec les pratiques des habitants, avant de proposer quelques pistes pour l’action
До відома авторів журналу «Питання історії науки і техніки»
Bry Xavier, Antoine Philippe.- Exploring the explanatory: an application to event history data This article presents an empirical plugging of factor analysis and generalized linear regression (logistic regression, Cox models, ...)■ We show that this combination can facilitate the exploration of complex data such as that on event histories (time-varying, censored) for modelling purposes. By combining a regression method with a new type of factor analysis — Thematic Components Analysis — we show how an explanatory conceptual model for the data can be included from the start of the exploratory phase. This method is then applied to an analysis of the divorce behaviour of men in Dakar, and used to give a simple illustration of each methodological point discussed.Bry Xavier, Antoine Philippe.- Explorer 1'explicatif : application à l'analyse biographique Ce travail relie de façon empirique analyses factorielles et régressions linéaires généralisées (régression logistique, de Cox, etc.). Nous montrons comment ce couplage permet de faciliter l'exploration de données complexes comme les données biographiques (variant dans le temps, incomplètement observées) en vue de leur modélisation. Nous associons une méthode de régression à une nouvelle méthode factorielle - l'analyse en composantes thématiques - qui permet de tenir compte, dès le départ, d'un modèle conceptuel explicatif des données. Cette méthode est ensuite appliquée à l'analyse du divorce des hommes à Dakar, ce qui permet d'illustrer simplement chaque point méthodologique abordé.Bry Xavier, Antoine Philippe.- Analizar las causas: aplicación al análisis biográfico En este articulo se relacionan de modo empírico análisis factoriales y regresiones linea- les generalizadas (regresión logística, de Сох, etc.). También se muestra como tal conexión facilita el análisis de datos complejos taies como los datos biográficos (que varian a través del tiempo y cuya observación es incompleta) y su modelización. Asociamos un método de regresión a un nuevo método factorial - el análisis de componentes temáticos - que permite tomar en cuenta, desde el principio, un modelo conceptual explicativo de los datos. A continuación aplicamos este método al análisis del divorcio masculino en Dakar para ilustrar de forma simple cada paso metodológico.Bry X., Antoine P. Exploring the explanatory: an application to event history data. In: Population (English edition), 59ᵉ année, n°6, 2004. pp. 795-830
Algorithms for computing norms and characteristic polynomials on general Drinfeld modules
We provide two families of algorithms to compute characteristic polynomials
of endomorphisms and norms of isogenies of Drinfeld modules. Our algorithms
work for Drinfeld modules of any rank, defined over any base curve. When the
base curve is , we do a thorough study of the
complexity, demonstrating that our algorithms are, in many cases, the most
asymptotically performant. The first family of algorithms relies on the
correspondence between Drinfeld modules and Anderson motives, reducing the
computation to linear algebra over a polynomial ring. The second family,
available only for the Frobenius endomorphism, is based on a new formula
expressing the characteristic polynomial of the Frobenius as a reduced norm in
a central simple algebra
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