Investigation by laser doppler velocimetry of the effects of liquid flow rates and feed positions on the flow patterns induced in a stirred tank by an axial-flow impeller

The (ow patterns established in a continuously-fed stirred tank, equipped with a Mixel TT axial-(ow impeller, have been investigated bylaser Doppler velocimetry, for a high and a low value of mean residence time—mixing time ratio. The pseudo-two-dimensional axial– radial-velocityvector plots, as well as the spatial distributions of the tangential velocitycomponent and the velocitypro;les around the impeller, show that the interaction between the incoming liquid and the liquid entrained bythe agitator rotation cause the (ow pattern in the vessel to become stronglythree-dimensional, especiallyin the region between the plane, where the feeding tube lies, and the 180◦-downstream plane. The increase in the liquid (ow rate and the location of the feed entryboth a$ect the (ow pattern, with the latter having a more pronounced e$ect. The overall process, in this mode of operation, depends upon the appropriate con;guration and choice of parameters: for conditions corresponding to high liquid (ow rates, the (ow patterns indicate the possibilityof short-circuiting, when the liquid is fed into the stream being drawn bythe agitator and when the outlet is located at the bottom of the vessel

Disposal of hypergolic propellants. phase 6, task 3: Prototype disposal pond

The design and operation of a prototype diposal of hypergolic propellants waste are described. Experiments with water hyacinths were performed

The conservation equations for multicomponent gas mixtures in arbitrary coordinate systems

The conservation equations for multicomponent reacting gas mixtures are generally given only in Cartesian or orthogonal curvilinear coordinate systems. Actually, the conservation equations are easily expressed in an arbitrary coordinate system. We present the general equations in tensor notation and then indicate the simplifications which arise for orthogonal curvilinear coordinates

Singularities of plane complex curves and limits of K\"ahler metrics with cone singularities. I: Tangent Cones

We construct and classify, in the case of two complex dimensions, the possible tangent cones at points of limit spaces of non-collapsed sequences of K\"ahler-Einstein metrics with cone singularities.Comment: Reference to Panov's Polyhedral Kahler Manifolds adde

Theatre and activism: the agit prop theatre way

Agit prop or agitational propaganda, as the very term implies, seeks to deliberately change people’s beliefs through well-planned strategies of persuasion, transformations of spectators into (spect)actors, and their subsequent mobilisation into agitating communities. Theatre is one of the channels of the agit prop. The emphasis on the deliberateness of the communication involved distinguishes this form of theatre from other forms of political theatre and from mere conversation. Many accusations have been levelled at agit prop theatre. Of these, the three primary ones are, first, that such theatre lacks artistic viability; second, that it is short-lived and works only in a certain historical context; and third, that it is only propaganda, not theatre. This paper challenges these accusations by investigating how agit prop theatre can evolve and undergo considerable artistic development to survive as good theatre and not just as good propaganda. Although agit prop does generally emerge in moments of crisis and in periods of revolutionary change, this does not imply that its value is erased once the moment passes. A good agit prop theatre company cannot, in fact, sustain itself on mere propaganda. As a case study, the paper will examine the work of the British forty-two year old Red Ladder Theatre Company. By examining in depth the specific aesthetic and dramaturgic ingredients that Red Ladder uses to achieve its aims, this article will demonstrate that artistic intent and application cannot be made subordinate to the revolutionary message, at least not for long

Un schéma vaut-il mieux qu'un long discours ?

International audienceThis research focuses on written language and systems of signs to study the learning of scientific concepts. It proposes to show that students (Grade 10 [aged 15]) mobilize ideas about gas in different ways in regard to the semiotic registers (text or picture) proposed during an assessment. Our study adopts a socio-constructivist approach of learning and develops a theoretical framework, articulating elements from the didactic of physics with semiotics concepts of Duval (1995). We give a test with questions (using simultaneously text and diagram) to approximately 90 students just after a teaching sequence on gas. We categorize with the software Sphinx students’ answers and diagram. This analysis has excellent intra-analyst reliability of our coding with the best level of reproducibility (Cohen’s Kappa test) and all our results are statistically significant (test of Khi2). Our results show that : (I) situations affect the mobilization of students’ ideas in regard to the semiotics registers involved in the assessment, (II) the semiotics registers have an effect on the mobilization of students’ ideas according to the facets of knowledge. Students are much more efficient in the register of : (a) schema to use facets about particles contained in gas and it homogeneous distribution and (b) text to mobilize their ideas about the action of gas, (III) the semiotic registers used in the tasks of the teaching sequence on gas could possibly be related to the mobilization of students’ ideas in the semiotics registers involved during the assessment. The implications of this work in teaching and research in didactic of physics are important. It allows to have a better consideration of the semiotic register to assess students’ knowledge.Cette recherche s’intéresse à l’importance du langage écrit et des systèmes de signes dans l’apprentissage de concepts scientifiques. Elle propose de montrer que la mobilisation des idées des élèves de seconde sur les gaz diffère selon les registres sémiotiques (texte ou schéma) proposés dans une évaluation. Notre étude adopte une approche socioconstructiviste de l’apprentissage et développe un cadre théorique mixte, articulant des éléments issus de la didactique de la physique avec les travaux de Duval (1995) sur la sémiotique. À partir d’une évaluation (utilisant simultanément du texte et du schéma) passée auprès d’environ 90 élèves de seconde juste après une séquence d’enseignement du groupe SESAMES sur les gaz, nous avons catégorisé à l’aide du logiciel Sphinx leurs réponses écrites et leurs schémas. La fiabilité de cette catégorisation a été éprouvée à l’aide du test de Cohen’s Kappa dont les résultats ont montré une excellente reproductibilité intra codeur. Nos résultats montrent par ailleurs que : (I) les situations influencent la mobilisation des idées des élèves en fonction des registres sémiotiques sollicités dans l’évaluation ; (II) les registres sémiotiques influencent différemment la mobilisation des idées des élèves en fonction des facettes du savoir mises en jeu. En effet, les productions des élèves sont beaucoup plus pertinentes : (a) dans le registre du schéma pour rendre compte des facettes aspect particulaire et répartition homogène du gaz et (b) dans le registre du texte en langage naturel pour mobiliser leurs idées relatives à l’action du gaz ; (III) les registres sémiotiques utilisés dans les tâches de la séquence d’enseignement sur les gaz pourraient éventuellement avoir un lien avec la mobilisation des idées des élèves dans les registres sémiotiques proposés par l’évaluation. Les implications de ces travaux dans l’enseignement de la physique, ainsi que la recherche en didactiques sont importantes. Elles devraient permettre une meilleure prise en compte des registres sémiotiques dans l’évaluation des connaissances des élèves

Les manuels récents de français langue étrangère : entre perspective actionnelle et approche communicative

In order to trace the emergence of the influence of an action-oriented approach to language teaching and learning, this paper presents an examination of activities proposed by three recent French textbooks. The textbooks treated are still very much grounded in the communicative approach, although to varying degrees, while they attempt to move towards a more action-oriented pedagogy. The interest of observing these “transitional” textbooks is that such an examination can reveal differences and similarities in logic with regards to the approach and also what might be modified in terms of teaching practice in the future. The paper concludes by raising the issue of how to construct phases in textbook teaching units within the logical framework of an action-oriented approach and proposes different models of organisation

Quel est l'impact des registres sémiotiques sur l'efficacité d'une séquence d'enseignement sur les gaz pour des élèves de Seconde ?

This research be interested in written language and sign systems in learning scientific concepts. It will show that the effectiveness of teaching about the gas on students varies with semiotic registers, as text or diagram. Our theoretical framework is in physics education and adopts a socio-constructivist approach using work on the semiotic. Based on a pre and post test (using text and diagram) given to 90 students at the upper-secondary school level (Grade 10 [15-year-old students]), we analyzed their responses with the Sphynx software. Our analysis is reproducible and all our results are statistically significant at the Chi2 test. Its show that after teaching students progress more and are much more efficient: (a) in the diagram to use ideas on particle aspect and the uniform distribution of gas and (b) in the written text to mobilize ideas on the action of the gas. Furthermore, it seems that there is a probable influence between semiotic registers used during teaching on a specific concept about gas and the importance of the evolution of students' ideas on this concept in the same semiotic register.Cette recherche s'intéresse à l'importance du langage écrit et des systèmes de signes dans l'apprentissage de concepts scientifiques. Elle propose de montrer que l'efficacité d'un enseignement à propos des gaz sur des élèves de seconde varie en fonction des registres sémiotiques du texte ou du schéma. Notre cadre théorique se situe dans la didactique de la physique et adopte une approche socio-constructiviste utilisant des travaux sur les registres sémiotique. À partir d'un pré et d'un post questionnaire (utilisant simultanément du texte et du schéma) passé auprès d'environ 90 élèves de Seconde, nous avons analysé leurs réponses avec le logiciel Sphynx. Notre analyse est reproductible et l'ensemble de nos résultats sont statistiquement significatifs au test du Khi2. Ils montrent qu'après enseignement les élèves progressent plus et sont beaucoup plus performant : (a) dans le registre du schéma pour utiliser des idées sur l'aspect particulaire et la répartition homogène des gaz et (b) dans le registre des réponses écrites en langage naturel pour mobiliser celles sur l'action du gaz. De plus, il semble qu'il y ait une influence probable entre les registres sémiotiques utilisées pour travailler une notion dans l'enseignement et l'importance de la progression des idées des élèves sur cette notion dans ces mêmes registres sémiotiques