MODELLING THE COMBUSTION CHAMBER OF AN ALUMINIUM CASTING FURNACE: A METHODOLOGY

Mathematical modelling of the phenomena occurring in a combustion chamber is a very difficult task. Recently, computational methods have been developed allowing the simulation of all the processes involved in a more elaborate and reliable manner than ever before. These methods however often present weaknesses originating from their lack of gener- ality and prohibitive computation time. Our aim was to come up with a technique that could be applied to rectangular furnaces of any size and characteristics, and that would require a reasonable computation time. The technique is based on combining the PHOENICS code (used for velocity and combustion fields) with a new radiation method, the so-called imaginary planes method. Results are presented for an aluminium melter/holder furnace. Comparison between the imaginary planes method and the zone method illustrates the excellent agree- ment obtained for the radiative transfer. The technique used for the coupling of PHOENICS with the radiative part is explained. Provisions are made to take care of the unsteady state regime often encountered in such furnaces where several different operations are performed in a row. The simulation of a transient operation is presented and it is found that a single determination of the velocity pattern on the basis of a steady state assumption is sufficient to simulate adequately time dependent gas temperature and heat flux distributions

Effectiveness of active school transport interventions : a systematic review and update

Background: Active school transport (AST) is a promising strategy to increase children's physical activity. A systematic review published in 2011 found large heterogeneity in the effectiveness of interventions in increasing AST and highlighted several limitations of previous research. We provide a comprehensive update of that review. Methods: Replicating the search of the previous review, we screened the PubMed, Web of Science, Cochrane, Sport Discus and National Transportation Library databases for articles published between February 1, 2010 and October 15, 2016. To be eligible, studies had to focus on school-aged children and adolescents, include an intervention related to school travel, and report a measure of travel behaviors. We assessed quality of individual studies with the Effective Public Health Practice Project quality assessment tool, and overall quality of evidence with the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) approach. We calculated Cohen's d as a measure of effect size. Results: Out of 6318 potentially relevant articles, 27 articles reporting 30 interventions met our inclusion criteria. Thirteen interventions resulted in an increase in AST, 8 found no changes, 4 reported inconsistent results, and 5 did not report inferential statistics. Cohen's d ranged from -0.61 to 0.75, with most studies reporting "trivial-to-small" positive effect sizes. Three studies reported greater increases in AST over longer follow-up periods and two Safe Routes to School studies noted that multi-level interventions were more effective. Study quality was rated as weak for 27/30 interventions (due notably to lack of blinding of outcome assessors, unknown psychometric properties of measurement tools, and limited control for confounders), and overall quality of evidence was rated as low. Evaluations of implementation suggested that interventions were limited by insufficient follow-up duration, incomplete implementation of planned interventions, and limited access to resources for low-income communities. Conclusions: Interventions may increase AST among children; however, there was substantial heterogeneity across studies and quality of evidence remains low. Future studies should include longer follow-ups, use standardized outcome measures (to allow for meta-analyses), and examine potential moderators and mediators of travel behavior change to help refine current interventions. Trial registration: Registered in PROSPERO: CRD4201603325

Âge de la déglaciation finale et histoire postglaciaire de la végétation dans la partie centrale du Nouveau-Québec

L'analyse poliinique, l'analyse macrofossile, ainsi que la datation au radiocarbone de quatre carottes de sédiments lacustres postglaciaires, ont permis d'établir l'âge minimal de la déglaciation et l'histoire postglaciaire de la végétation dans la partie centrale du Nouveau-Québec, où ont persisté quelques-uns des derniers lambeaux de la calotte glaciaire wisconsinienne au Québec. La déglaciation s'est échelonnée entre 6200 ans BP, qui représente l'amorce de la stagnation finale au sud-ouest de la ligne de partage glaciaire terminale, et 5600 ans BP, qui représente l'âge minimal de la fusion finale de la glace, en terre haute, au nord-est de la ligne de partage. Le délai entre la disparition de la glace et l'accumulation des premiers sédiments organiques datables dans les petits lacs a été très court. La colonisation végétale fut immédiate, relativement massive, tant par les arbres et les arbustes que par les plantes herbacées. L'aulne crispé (Alnus crispa) et le mélèze (Larix laricina) dominèrent au début, mais toutes les autres espèces d'arbres étaient déjà présentes. Une taïga à épi-nette noire (Picea mariana) beaucoup plus dense qu'aujourd'hui a occupé le paysage entre 5500 et 4400 ans BP environ. Le principal trait de l'histoire postglaciaire de la végétation est l'ouverture généralisée de la couverture arbo-réenne et arbustive, qui s'amorce vers 4700 à 4300 ans BP reflétant sans doute l'avènement d'un climat plus froid. La seule indication d'une éventuelle fluctuation climatique est représentée par deux périodes de plus grande abondance du bouleau blanc, entre 5750 et 4750 ans et entre 3600 et 2500 ans enregistrées en un site de la région.Pollen and macrofossil analyses, as well as radiocarbon dating, of four cores of postglacial lake sediments collected from central Nouveau-Québec, provide an estimate of the minimum age for the disappearance of some of the last remnants of the Wisconsinan ice in Québec, and allow a reconstruction of the postglacial history of the vegetation. The final stages of déglaciation span from about 6200 to about 5600 years BP. The first date marks the time of inception of the final stagnation of the ice southwest of the terminal ice-divide and the second gives the minimum age of the final melting of the ice on the uplands north of the divide. The time which elapsed between the uncovering of the cored lake basins by the ice and the accumulation of datable organic matter in these was short due to the rapid colonisation of the newly uncovered land by trees, shrubs and herbs. Green alder (Alnus crispa) and larch (Larix laricina) dominated the landscape at first, but all the other species of trees and shrubs were already present. From ca. 5500 to 4400 years BP, the region supported a dense black spruce (Picea mariana) taiga. The main feature of the subsequent postglacial history of the vegetation is the opening of the arboreal cover around 4700 to 4400 years BP reflecting the cooling of the regional climate. The only indication of possible postglacial climatic fluctuations other than the general cooling trend are represented by two pollen influx pulses of white birch (Betula papyrifera) between 5760 and 4750 years BP and between 3600 and 2500 years BP, recorded at one of the sites

The origin of the E+ transition in GaAsN alloys

Optical properties of GaAsN system with nitrogen concentrations in the range of 0.9-3.7% are studied by full-potential LAPW method in a supercell approach. The E+ transition is identified by calculating the imaginary part of the dielectric function. The evolution of the energy of this transition with nitrogen concentration is studied and the origin of this transition is identified by analyzing the contributions to the dielectric function from different band combinations. The L_1c-derived states are shown to play an important role in the formation of the E+ transition, which was also suggested by recent experiments. At the same time the nitrogen-induced modification of the first conduction band of the host compound are also found to contribute significantly to the E+ transition. Further, the study of several model supercells demonstrated the significant influence of the nitrogen potential on the optical properties of the GaAsN system.Comment: 5 pages, 3 figure

Near Peer Learning To Facilitate Nursing Students’ First Medical Surgical Clinical Experience / Apprentissage par les pairs proches de manière à faciliter les premières expériences cliniques en médecine et chirurgie pour les étudiantes en sciences infirmières

Introduction and Background: Ensuring an appropriate clinical experience for students is becoming more challenging in the context of a global nursing shortage, more acutely ill clientele, and limited numbers of educators, academics and clinical instructors. Near Peer Learning Activities (NPLA) have been shown to be effective and may help students to feel prepared and confident to begin the clinical rotation. This study explored nursing students’ experiences in their first medical-surgical practicum following a NPLA involving Health and Physical Assessment (HPA). Methods: Educators at one Canadian University recently designed and implemented a NPLA in the clinical setting where junior nursing students performed a focused health and physical assessment on a patient, in an acute medical-surgical unit with the guidance of senior students. Ten nursing students who took part in the NPLA were individually interviewed. Thematic content analysis was used to generate the themes. Findings: Following the NPLA, two main themes captured the essence of the students’ experience: (1) making nursing real through near peer learning and (2) surmounting personal and contextual challenges in a first medical-surgical experience. Students “owned” their HPA skills, felt excited and prepared entering their medical-surgical placement. During the experience, however, students worried about not measuring up and the unreceptive learning environment. Conclusion: The NPLA provided a safe context for novice students to apply HPA and become familiar with the hospital setting, facilitating their transition into a challenging first medical-surgical practicum. Résumé Introduction et contexte : Assurer une expérience clinique appropriée aux étudiantes devient de plus en plus difficile dans le contexte d’une pénurie généralisée d’infirmières, d’une clientèle plus gravement malade et d’un nombre limité d’enseignantes, de professeures et de formatrices cliniques. L’efficacité d’activités d’apprentissage par les pairs proches (en anglais, Near Peer Learning Activities ou NPLA) a été mise en évidence; ces activités pourraient aider les étudiantes à se sentir plus confiantes et prêtes à débuter leurs stages cliniques. Cette étude a exploré les expériences d‘étudiantes en sciences infirmières lors de leur premier stage médico-chirurgical à la suite d’une activité d’apprentissage par les pairs proches quant à l’évaluation physique et de la santé (en anglais, Health and Physical Assessment ou HPA). Méthodologie : Les professeures d’une université canadienne ont récemment conçu et mis en place des activités d’apprentissage par les pairs proches dans un environnement clinique où des étudiantes infirmières débutantes dans une unité médico-chirurgicale de soins de courte durée effectuaient une évaluation physique et de la santé ciblée d’un patient avec l’aide d’étudiantes plus avancées dans leur programme. Des entrevues individuelles furent effectuées avec dix étudiantes en sciences infirmières qui avaient participé aux activités d’apprentissage par les pairs proches. L’analyse thématique de contenu a été utilisée pour générer les thèmes. Résultats : Les activités d’apprentissage par les pairs proches ont permis d’identifier deux thèmes principaux qui englobaient l’expérience des étudiantes : (1) concrétiser les soins infirmiers grâce à un apprentissage par les pairs proches; et (2) relever des défis personnels et contextuels lors d’une première expérience médico-chirurgicale. Les étudiantes « s’appropriaient » leurs habiletés en matière d’évaluation physique et de la santé, et étaient motivées et préparées à entrer dans leur stage médico-chirurgical. Au cours de l’expérience, cependant, les étudiantes se sont inquiétées de ne pas être à la hauteur et de se buter à un environnement d’apprentissage peu réceptif. Conclusion : Les activités d’apprentissage par les pairs proches ont créé un contexte sûr pour que les étudiantes novices mettent en pratique l’évaluation physique et de la santé et se familiarisent avec le milieu hospitalier, facilitant ainsi leur transition vers un premier stage médico-chirurgical stimulant

Illustrer le territoire québécois dans les manuels d’histoire au secondaire : étude de cas sur le paysage en tant qu’outil de médiation culturelle et ses rapports avec l’espace, le pouvoir et l’identité

Dans le présent article, nous proposons une réflexion sur l’usage du paysage dans trois manuels d’histoire québécois. Nous l’abordons premièrement en considérant le cadre de référence (ou le contexte de production) de ces documents visuels, de nature artistique, scientifique ou médiatique,relatifs à l’architecture. Nous analysons ces trois types de paysages pour discuter des rapports qu’ils entretiennent avec le réel, notamment concernant un certain effet d’authenticité et d’objectivité. Il s’agit alors de considérer le paysage en tant qu’outil de médiation culturelle. Nous poursuivons la réflexion sur l’usage du paysage par une analyse thématique de lieux associés à la ville de Montréal dans les manuels. Ensuite, nous présentons une grille de lecture des documents iconographiques qui pourrait s’appliquer à tout paysage considéré comme document iconographique pour susciter un questionnement productif sur le plan des informations que l’on peut en tirer. In this paper, we propose a reflection on the use of the landscape in three Quebec history textbooks. We turn first considering the terms of reference (or the context of production) of these visual documents, produced from an artistic, scientific or mediatic point of view. We analyze these three types of landscapes to discuss their relationship with reality, especially regarding some effect of authenticity and objectivity. It is then to consider the landscape as a tool for cultural mediation. We continue the reflection on the use of the landscape by a thematic analysis of places associated with the city of Montreal in textbooks. Thirdly, we present a reading grid of graphic materials that could be applied to any landscape considered as graphic material, in order to question it in terms of information that can be learned

The rings of n-dimensional polytopes

Points of an orbit of a finite Coxeter group G, generated by n reflections starting from a single seed point, are considered as vertices of a polytope (G-polytope) centered at the origin of a real n-dimensional Euclidean space. A general efficient method is recalled for the geometric description of G- polytopes, their faces of all dimensions and their adjacencies. Products and symmetrized powers of G-polytopes are introduced and their decomposition into the sums of G-polytopes is described. Several invariants of G-polytopes are found, namely the analogs of Dynkin indices of degrees 2 and 4, anomaly numbers and congruence classes of the polytopes. The definitions apply to crystallographic and non-crystallographic Coxeter groups. Examples and applications are shown.Comment: 24 page

Nonlinear magnetoinductive transmission lines

Power transmission in one-dimensional nonlinear magnetic metamaterials driven at one end is investigated numerically and analytically in a wide frequency range. The nonlinear magnetic metamaterials are composed of varactor-loaded split-ring resonators which are coupled magnetically through their mutual inductances, forming thus a magnetoiductive transmission line. In the linear limit, significant power transmission along the array only appears for frequencies inside the linear magnetoinductive wave band. We present analytical, closed form solutions for the magnetoinductive waves transmitting the power in this regime, and their discrete frequency dispersion. When nonlinearity is important, more frequency bands with significant power transmission along the array may appear. In the equivalent circuit picture, the nonlinear magnetoiductive transmission line driven at one end by a relatively weak electromotive force, can be modeled by coupled resistive-inductive-capacitive (RLC) circuits with voltage-dependent capacitance. Extended numerical simulations reveal that power transmission along the array is also possible in other than the linear frequency bands, which are located close to the nonlinear resonances of a single nonlinear RLC circuit. Moreover, the effectiveness of power transmission for driving frequencies in the nonlinear bands is comparable to that in the linear band. Power transmission in the nonlinear bands occurs through the linear modes of the system, and it is closely related to the instability of a mode that is localized at the driven site.Comment: 11 pages, 11 figures, submitted to International Journal of Bifurcation and Chao

Asymmetric total synthesis of (+)-virosine a via sequential nucleophilic cyclizations onto an activated formamide

Abstract: The first synthesis of tetracyclic alkaloid virosine A is reported. The natural alkaloid was prepared in only 13 steps, in an enantioenriched form. The azabicyclo[2.2.2]octane core was efficiently assembled using a key Vilsmeier–Haack and Mannich cyclizations sequence performed in one pot