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Nouveau mode de représentation graphique de l'équilibre calco-carbonique Application au traitement des eaux

Cet article traite des problèmes liés à l'étude des équilibres calco-carboniques en limitant leur présentation à l'aspect purement graphique. Dans cette optique, on a développé un nouvel abaque original en choisissant comme coordonnées pH et [CO3 total].La construction d'un tel abaque ne fait appel qu'à 2 lois fondamentales, à savoir : a) la relation du produit de solubilité du carbonate calcique :Ks=Y22[Ca2+[CO2-3]Cette dernière peut, moyenant l'introduction d'une variable auxiliaire :∆=[Ca2+]-[CO3 total]se transformer en une relation équivalente plus commode pour le calcul des courbes constitutives de l'abaque.b) une deuxième relation, prenant en compte les ions H+ soit libres, soit engagés dans des combinaisons avec le groupe carbonate ou avec le solvant H2 O. Dans ce but, on introduit une concentration totale appelée acidité potentielle totale (en abrégé APT) définie de la sorte :APT=2[H2CO3]+[HCO-3]+[H2O]+[H+]En outre, on utilise une variable dérivée de APT à laquelle on a donné le nom d'acidité potentielle carbonatée et le symbole. Sa définition est la suivante :δ=2[H2CO3]+[HCO-3]Les 2 variables et APT jouissent en commun de la propriété intéressante de rester invariantes lors de la mise en équilibre de l'eau selon l'équation :CaCO3+H+⇌Ca2++HCO-3La variable peut également être considérée comme pratiquement invariante dans le domaine des eaux naturelles.Cette propriété est mise à profit pour construire 2 réseaux de courbes constitutives de l'abaque, à savoir :a) celles satisfaisant à la condition : APT=constante. Ces dernières seront appelées "courbes d'iso-aciditéb) celles répondant à la condition : ∆=constante.On les désignera sous le nom de "courbes d'iso-équilibre"L'article s'attache à décrire le mode d'utilisation de cet abaque tout en mettant en valeur sa facilité d'emploi pour l'évaluation, tant qualitative que quantitative du comportement d'une eau à l'égard du carbonate calcique.En particulier, la technique permet de visualiser les caractéristiques essentielles de l'eau telles que pH équilibrant, pH stabilisant et indice de stabilisation, caractéristiques dont la signification est précisée dans l'article.L'abaque en question, en parallèle avec un logiciel qui peut lui être associé, constitue ainsi un outil précieux tant pour caractériser une eau que pour procéder ensuite aux traitements chimiques les plus connus.Le cas du mélange d'eaux peut également être avantageusement traité par le biais de cet abaque. De nombreux exemples d'application aux traitements de l'eau sont également largement développés dans la publication. Ceux-ci devraient aider grandement ceux qui sont confrontés aux divers problèmes de l'industrie de l'eau.L'analyse graphique constitue par ailleurs une excellente introduction à la gestion informatisée plus complète de ces problèmes et dont le traitement ne pouvait trouver place dans le cadre limité de cette publication.Le lecteur désireux de poursuivre ces développements ou d'avoir accès au programme informatique complémentaire à cette étude, trouvera les indications nécessaires dans les références bibliographiques figurant en fin de l'article.Although many good methods exist for computing calcium-carbonate equilibria, we considered that it was still possible to improve the representation to the problem and for this reason we have developed a new method of calculation. In this paper we have restricted ourselves to the graphical aspect of the question, referring the reader to the original bibliography at the end of the paper and as well we have not taken into account the kinetic aspects of the reactions involving the dissolution or precipitation of CaCO3.From this perspective, an original graph has been designed choosing for co-ordinates the pH (abscissa) and [CO3 total] (ordinate). The construction of such a graph requires only two fundamental laws, i.e.1) The solubility product relationship of calcium carbonate. This relationship, with the introduction of an auxiliary variable:∆=[Ca2+] - [CO3 total]can be transformed itself into an équivalent relationship, more convenient for the computation of the various curves composing the graph.2) A second relationship, taking into account the H+-ions in their free or bound state (with the C03 group or the H20 solvent). For this purpose, one introduces a total concentration, called potential total acidity (in abbreviated form PTA), the définition of which is:PTA=2[H2CO3]+[HCO-3]+[H2O]+[H+]In addition, one uses also another variable derived from PTA to which we gave the name : carbonated potential acidity with the following definition:δ=2[H2CO3]+[HCO-3]Both variables PTA and ∆ have jointly the interesting property of remaining constant during the evolution of the water towards equilibrium according to the equation: CaCO3+H+⇌Ca2++HCO-3The variable may also be considered as practically constant in the field of natural waters. We have taken advantage of this property to build up two networks of curves that make up the overall graph, i.e., a) the curves satisfying the condition : PTA=constant (these curves are named " iso-acidity curves "), and b) the curves whose characteristics are : =constant, and which are named " iso-equilibrium curves ".The paper describes how to use the graph and brings out its ease of use for both the qualitative and quantitative prediction of the behaviour of water in contact with calcium carbonate. In particular, the graph illustrates such essential water characteristics as equilibrium pH, stabilisation pH and stabilisation index, characteristics whose meanings are defined in the paper. The graph is shown to be a useful tool for the characterisation of waters as well as for the evaluation of most chemical treatments. The case of the mixture of different waters is also treated. Numerous examples for using the graph under different circumstances are developed in the paper, which should be useful for those whose job is connected with industrial water treatment. The graphical method here described, in conjunction with an associated computer programme, also constitutes an excellent introduction to the more complete computing methods developed elsewhere but which could not be treated in the limited frame of this publication.The graph turns out to be a useful tool for the characterisation of waters as well as for the evaluation of different chemical treatments, such as softening, carbonation, decarbonation, acidification, alkalinisation, aeration, etc. The case of the mixture of different waters is also treated. Numerous examples for using the graph under different circumstances are developed. The paper shows how it is possible, on the basis of the diagram, to predict the evolution of the water when different reagents are added, when the temperature changes or when one mixes different waters. The diagram should be a useful aid for those people whose job is connected with industrial water treatment.A computing program is necessary to draw the curves, to obtain the water characteristics with a better accuracy than can be read from the graphs. This programme, named Carbeq+, is commercially available (see below for the bibliographical reference). The values necessary for the computation and the drawing of the curves are :1. temperature of analysis and temperature of computation2. pH, alkalinity, calcium concentration3. the ionic strength, which can be calculated either from the knowledge of the complete analysis of the water, or if that one is not available, by using an empirical relation based on either the conductivity or the salt content. The program computes then the equilibrium pH, the stabilisation pH and the stabilisation index and draws the graphs described in the paper. The graphical method here described, in conjunction with the associated computer programme, constitutes also an excellent introduction to the more complete computing methods developed elsewhere but which could not be treated in the limited frame of this publication. Note that the case of the influence of the gaseous carbon dioxide phase on the equilibrium is not treated in this paper, but it is taken into account in the Carbeq+ programme mentioned above

Approche culturelle et écriture réflexive pour un public Lansad

Nous nous intéressons aux difficultés culturelles des étudiants en mobilité à l'École des Ponts ParisTech, pour les aider, dans un module intégrant les TIC, à mieux s'adapter à la communauté française de l'école. Les apprenants ont produit un journal de bord, ce qui implique la mise en place d'un apprentissage par l'exploration et une prise de conscience, que l'on sera le « maître » de sa formation. Notre analyse montrera comment ils se sont investis dans la formation. Nous mettrons en valeur le cheminement personnel et une certaine relativisation culturelle. Nos résultats permettent de compléter les travaux antérieurs et montrent en quoi le journal de bord est un outil pertinent pour le public spécifique des grandes écolesOur approach deals with both navigating the cultural difficulties incoming students to the École des Ponts ParisTech may experience, and designing and implementing a module using Internet. A central part of the module was journal writing by the students. It allows the learner to relate his/her actual experience and thoughts. Our results complement former research and emphasize the fact that journals follow the learner's personal line of thought and reflect his/her process of cultural assimilation. This article focuses on the way learners have reacted to this task and how they put a lot of effort into doing the journal (self-assessment and learner's journal). This paper shows how a journal is a relevant tool for the specific public of a French graduate Engineering school

Somatosensory evoked potentials as an objective assessment of the sensory median nerve blockade after infraclavicular block

Purpose: Median nerve somatosensory evoked responses (MnSSER) alterations were compared to clinical tests (cold and pinprick) variations, in 20 ASA I adult patients following infraclavicular block obtained with 40 mL ropivacaine 0.5% to assess first, the difference of time course of the respective electrophysiological and clinical signs, and second, the objectivity and the reproducibility of MnSSER changes. Clinical features: Four MnSSER derivations (Erb's point; cutaneous projection of peripheral end of brachial plexus; posterior neck at C6 level, frontal and controlateral parietal scalp) were monitored and recorded for retrospective analysis. Continuous data acquisition were started before ropivacaine injection (baseline) and maintained for 30 min thereafter. Every three minutes after ropivacaine injection, cold and pinprick tests were performed in the hand median nerve cutaneous supply zone and were assessed using a sensory visual score (varying from 0-10). Data were compared using analysis of variance. Although MnSSER values were stable during baseline period, after ropivacaine administration, severe progressive amplitude depressions of selected MnSSER were detected in every patient. While clinical cold and pinprick tests became positive (score > 8) only 15.8 ± 1.2 min and 20.1 ± 1.8 min respectively after ropivacaine administration, the mean time to observe the earliest MnSSER 20% amplitude decrease at Erb's point derivation was reduced to 5.6 ± 1.1 min (P < 0.01). Conclusion: Selected MnSSER amplitude reduction indicates objectively the onset of median nerve anesthesia following infraclavicular brachial plexus block before the appearance of clinical sign

El análisis del trabajo treinta años después de Ombredane y Faverge

El análisis del trabajo de Ombredane y Faverge había desarrollado en 1955 una metodología original que situaba la selección, formación y cualificación del trabajo junto a la organización estricta de este. Los autores explicitan tres ideas que han surgido desde entonces y que son todavía el fundamento de las investigaciones en esta materia : el análisis del trabajo debe distinguir entre el análisis de la tarea y el análisis de la actividad ; ambos análisis presentan una metodología específica y cualquier análisis del trabajo debe asumir nuevos factores que actúan en interacción, es decir, la toma de poder del hombre sobre su actividad si no sobre su tarea, la influencia de la crisis económica y sus repercusiones y el desarrollo de las técnicas informáticas y derivadas

Data‑driven learning for languages other than English: the cases of French, German, Italian, and Spanish

. This paper summarises the contributions to EuroCALL’s CorpusCALL SIG Symposium for the year 2020. In line with this year’s EuroCALL conference theme, ‘CALL for widening participation’, the Symposium centred around thetheme of Data-driven learning for languages other than English. This paper gives a brief overview of developments and challenges when using Data-Driven Learning(DDL) to teach French, German, Italian, and Spanish. As research suggests, a DDL approach has been effectively utilised to teach these languages. However, there are differences in available DDL resources and corpora for the respective languages that are appropriate for language teaching. The main challenges for future developments are also discussed. K.‑M. Frederiksen, S. Larsen, L. Bradley &amp; S. Thouësny (Eds), CALL for widening participation: short papers from EUROCALL 2020 (pp. 132‑137). Research‑publishing.net. https://doi.org/10.14705/rpnet.2020.48.117

Ergonomie, régulation et pouvoir

Laboratoire de Psychologie Industrielle et Commerciale, Université Libre de Bruxelles, Bruxelles, 1971, 13 p.info:eu-repo/semantics/publishe

Problèmes d'adaptation administrative

info:eu-repo/semantics/nonPublishe