A note on the consistency of Hybrid Eulerian/Lagrangian approach to multiphase flows

The aim of the present paper is to introduce and to discuss inconsistencies errors that may arise when Eulerian and Lagrangian models are coupled for the simulations of turbulent poly-dispersed two-phase flows. In these hydrid models, two turbulence models are in fact implicitely used at the same time and it is essential to check that they are consistent, in spite of their apparent different formulations. This issue appears in particular in the case of very-small particles, or tracer-limit particles, and it is shown that coupling inconsistent turbulence models (Eulerian and Lagrangian) can result in non-physical results, notably for second-order fluid velocity moments. This problem is illustrated by some computations for fluid particles in a turbulent channel flow using several coupling strategies.Comment: 14 pages, 3 figure

A Review of H2CO 6cm Masers in the Galaxy

We present a review of the field of formaldehyde (H2CO) 6cm masers in the Galaxy. Previous to our ongoing work, H2CO 6cm masers had been detected in the Galaxy only toward three regions: NGC7538 IRS1, Sgr B2, and G29.96-0.02. Current efforts by our group using the Very Large Array, Arecibo, and the Green Bank Telescope have resulted in the detection of four new H2CO 6cm maser regions. We discuss the characteristics of the known H2CO masers and the association of H2CO 6cm masers with very young regions of massive star formation. We also review the current ideas on the pumping mechanism for H2CO 6cm masers.Comment: 10 pages, 5 figures, IAU Symposium 242: Astrophysical Masers and their Environment

Revisiting LFSMs

Linear Finite State Machines (LFSMs) are particular primitives widely used in information theory, coding theory and cryptography. Among those linear automata, a particular case of study is Linear Feedback Shift Registers (LFSRs) used in many cryptographic applications such as design of stream ciphers or pseudo-random generation. LFSRs could be seen as particular LFSMs without inputs. In this paper, we first recall the description of LFSMs using traditional matrices representation. Then, we introduce a new matrices representation with polynomial fractional coefficients. This new representation leads to sparse representations and implementations. As direct applications, we focus our work on the Windmill LFSRs case, used for example in the E0 stream cipher and on other general applications that use this new representation. In a second part, a new design criterion called diffusion delay for LFSRs is introduced and well compared with existing related notions. This criterion represents the diffusion capacity of an LFSR. Thus, using the matrices representation, we present a new algorithm to randomly pick LFSRs with good properties (including the new one) and sparse descriptions dedicated to hardware and software designs. We present some examples of LFSRs generated using our algorithm to show the relevance of our approach.Comment: Submitted to IEEE-I

Where the Girls Are: Trade and Labor Market Segregation in Colombia

Gary Becker's theory of discrimination argues that increasing competition will reduce discrimination in the labor market. We use the Colombian trade liberalization episode over the period 1984–91 to investigate this claim on plant-level data in three ways. First, we examine whether women are concentrated in exporting plants. Second, we examine whether the increase in foreign competition due to unilateral trade liberalization disproportionately drove discriminating plants out of the market. Finally, we investigate whether trade liberalization affected hiring decisions (and thus gender segregation) by Colombian firms.discrimination, trade, competition

Langevin PDF simulation of particle deposition in a turbulent pipe flow

The paper deals with the description of particle deposition on walls from a turbulent flow over a large range of particle diameter, using a Langevin PDF model. The first aim of the work is to test how the present Langevin model is able to describe this phenomenon and to outline the physical as- pects which play a major role in particle deposition. The general features and characteristics of the present stochastic model are first recalled. Then, results obtained with the standard form of the model are presented along with an analysis which has been carried out to check the sensitivity of the predictions on different mean fluid quantities. These results show that the physical repre- sentation of the near-wall physics has to be improved and that, in particular, one possible route is to introduce specific features related to the near-wall coherent structures. In the following, we propose a simple phenomenological model that introduces some of the effects due to the presence of turbulent coherent structures on particles in a thin layer close to the wall. The results obtained with this phenomenological model are in good agreement with experimental evidence and this suggests to pursue in that direction, towards the development of more general and rigorous stochastic models that provide a link between a geometrical description of turbulent flow and a statistical one.Comment: 40 pages, 8 figure

3D simulations of pillars formation around HII regions: the importance of shock curvature

Radiative feedback from massive stars is a key process to understand how HII regions may enhance or inhibit star formation in pillars and globules at the interface with molecular clouds. We aim to contribute to model the interactions between ionization and gas clouds to better understand the processes at work. We study in detail the impact of modulations on the cloud-HII region interface and density modulations inside the cloud. We run three-dimensional hydrodynamical simulations based on Euler equations coupled with gravity using the HERACLES code. We implement a method to solve ionization/recombination equations and we take into account typical heating and cooling processes at work in the interstellar medium and due to ionization/recombination physics. UV radiation creates a dense shell compressed between an ionization front and a shock ahead. Interface modulations produce a curved shock that collapses on itself leading to stable growing pillar-like structures. The narrower the initial interface modulation, the longer the resulting pillar. We interpret pillars resulting from density modulations in terms of the ability of these density modula- tions to curve the shock ahead the ionization front. The shock curvature is a key process to understand the formation of structures at the edge of HII regions. Interface and density modulations at the edge of the cloud have a direct impact on the morphology of the dense shell during its formation. Deeper in the cloud, structures have less influence due to the high densities reached by the shell during its expansion.Comment: Accepted by A&A 03/11/201

Des représentations de l’apprentissage de parents et d’enseignants d’élèves du primaire qui éclairent les interactions vécues

L’étude porte sur les représentations de l’apprentissage et les interactions parents-enseignants vécues dans le contexte de l’enseignement primaire. La théorie des représentations sociales, les paradigmes éducatifs et les théories actuelles en éducation servent de cadre conceptuel. Quinze dyades parents-enseignants interagissant au primaire constituent l’échantillon. Des sous-groupes ont été formés selon le type d’interaction vécue. Des entrevues ont été effectuées et une analyse des discours de type pragmatico-énonciative a été effectuée. L’analyse croisée apporte un éclairage sur les éléments représentationnels centraux suivants : l’intervention éducative, les conditions à l’apprentissage, le sujet et le rôle d’éducateur. En cas de négociation, les représentations s’harmonisent et l’interaction devient constructive ; autrement, c’est le conflit. L’appartenance paradigmatique éducationnelle des enseignants et des enseignantes explique le type d’interaction.This study examines parent-teacher representations of learning and their interactions in the context of primary level education. The conceptual frame includes the theory of social representations, educational paradigms, ands current educational theories. The sample included fifteen dyads of parent-teachers at the primary level. These formed sub-groups according to the type of interaction observed. Following the interviews, a “pragmatic-enunciated” discourse analysis was applied. An analysis allowed the author to highlight the following central representational elements: educational intervention, learning conditions, the educator and his role. In negotiation, representations become more harmonious and interactions more constructive; otherwise there is conflict. It seems that the educational paradigm held by teachers explains the type of interaction observed.El estudio tiene por objeto las representaciones del aprendizaje y las interacciones padres-docentes experimentadas en el contexto de la enseñanza primaria. La teoría de las representaciones sociales, los paradigmas educativos y las teorías actuales en educación sirven de marco conceptual. Quince díadas padres-docentes interactuando en la primaria constituyen la muestra. Se formaron unos subgrupos según el tipo de intervención experimentada. Se realizaron unas entrevistas y un análisis de los discursos de tipo pragmático-enunciativo. El análisis cruzado permite aclarar los siguientes elementos representacionales centrales: la intervención educativa, las condiciones de aprendizaje, el sujeto y el papel del educador. En caso de negociación, las representaciones se armonizan y la interacción se vuelve constructiva; de no ser así, surge el conflicto. La pertenencia paradigmática educacional de los docentes explica el tipo de interacción

NG7538 IRS1 N: modeling a circumstellar maser disk

We present an edge-on Keplerian disk model to explain the main component of the 12.2 and 6.7 GHz methanol maser emission detected toward NGC7538-IRS1 N. The brightness distribution and spectrum of the line of bright masers are successfully modeled with high amplification of background radio continuum emission along velocity coherent paths through a maser disk. The bend seen in the position-velocity diagram is a characteristic signature of differentially rotating disks. For a central mass of 30 solar masses, suggested by other observations, our model fixes the masing disk to have inner and outer radii of about 270 AU and 750 AU.Comment: To appear in The Proceedings of the 2004 European Workshop: "Dense Molecular Gas around Protostars and in Galatic Nuclei", Eds. Y. Hagiwara, W.A. Baan, H.J. van Langevelde, 2004, a special issue of ApSS, Kluwe

Questioning the ‘of’ in Performance-as-translation: Multimedia as a Subtext in the 2003 Pécs Performance ‘of’ Hamlet

This article explores a theatre performance (National Theatre Pécs, 2003, dir. Iván Hargitai) working with a 1999 Hungarian translation of Hamlet by educator, scholar, translator and poet Ádám Nádasdy as a structural transformation (Fischer-Lichte 1992) of the dramatic text for the stage. The performance is perceived as an intersemiotic translation but not as one emerging from a source-to-target one-way route. The study focuses on certain substructures such as the set design and the multimedial nature of the performance (as defined by Giesekam 2007), and by highlighting intertextual and hypertextual ways of accessing this performance-as-translation it questions the ‘of’ in the ‘performance of Hamlet (or insert other dramatic title)’ phrase. This experimentation with the terminology around performance-as-translation also facilitates the unveiling of a layer of the complex Hungarian Hamlet palimpsest, which, as a multi-layered cultural phenomenon, consists of much more than literary texts: its fabric includes theatre performance and other creative works