Effect of chemical reactions on the fluidic thrust vectoring of an axisymmetric nozzle

Abstract: During the last years, several thrust control systems of aerospace rocket engines have been developed. The fluidic thrust vectoring is one of them; it is simple in design and offers a substantial gain in weight and in performance. Most of studies related to this device were carried out with cold gas. It’s quite legitimate to expect that the thermophysical properties of the gases may affect considerably the flow behavior. Besides, the effects of reacting gases at high temperatures, under their effects all flow parameters like to vary. This study aims to develop a new methodology that allows studying and analyzing the fluidic thrust vectoring for a perfect gas, by taking into account the effects chemical reactions on the flow parameters, such as separation point, reattachment point downstream and pressure distribution upstream the injection port. In this study, the thrust vectorization implying frozen reacting hot gases was carried out by considering a chemical reaction mechanism. The thermodynamic parameters of the flow are calculated within the combustion chamber and different sections of the supersonic part of the nozzle. The results show a good agreement for cold gas, and as expected à slight difference for hot reacting gases. Performance analysis are conducted and basic conclusions are drawn in terms of thermodynamic gas properties effect on the fluidic thrust vector system. The primary effect was related to the gas molecular weight and its specific heat ratio. It is observed that for fixed injection conditions, the vectoring angle is different when the injected gas molecular weight and specific heat ratio are different. For a given mission of the launcher, it can be concluded that the mass of the embedded gas, used for the fluidic vectorization system, can be significantly reduced, depending on its molecular weight and specific heat ratio

Quand le bloc axillaire reste la seule alternative chez un enfant de 5 ans

Le bloc axillaire par neurostimulation chez l'enfant n'est pas une technique habituelle, surtout avec le développement des techniques d'anesthésie locorégionale échoguidées. Cependant elle peut être une alternative intéressante si l'anesthésie générale est a risque voir même contre indiquée. Nous rapportons le cas d'un bloc axillaire anesthésique chez un enfant de 5 ans porteur d'un kyste hydatique du poumon et une hépatite A sévère proposé pour une fixation de fracture du condyle externe de l'humérus.Keywords: Anesthésie pédiatrique, bloc axillaire, hépatite aigue, kyste hydatique pulmonair

L’école québécoise assure-t-elle l’égalité des chances ? Le cheminement scolaire des jeunes noirs au secondaire

Cet article présente les résultats du suivi de trois cohortes (1994, 1995, 1996) d’élèves francophones, anglophones et créolophones, nés dans les Antilles ou en Afrique ou dont au moins un des deux parents est né dans ces régions, de leur entrée à l’école secondaire québécoise de langue française jusqu’à l’obtention de leur diplôme au cégep. Ces élèves ont été comparés, d’une part avec l’ensemble des élèves et, d’autre part, avec l’ensemble des élèves issus de l’immigration (première et deuxième générations). Dans la première partie, les auteurs donnent un aperçu des caractéristiques sociales et éducatives des cinq sous-groupes. Leur expérience scolaire est ensuite décrite à l’aide des divers indicateurs disponibles dans les banques de données administratives du ministère de l’Éducation (âge à l’arrivée au secondaire; retard scolaire en secondaire 3; identification comme élève à besoins particuliers; taux d’obtention d’un diplôme après 5, 6 ou 7 ans de scolarité secondaire; accès au cégep et taux d’obtention d’un diplôme collégial. Finalement, les auteurs explorent l’impact d’un ensemble de variables socio-démographiques et scolaires sur les taux d’obtention d’un diplôme secondaire.This article presents the results of a systematic tracking of 3 cohorts (1994, 1995, 1996) of Francophone, Anglophone and Creolophone students, born in the West Indies or Africa, or who have at least one parent born in these regions, from their entrance in the secondary French language school system of Quebec through their diplomation at the end of junior college. These students are compared with the entire school population and the sub-group of first and second generation immigrant students. In the first part, the authors give an overview of the social and educational characteristics of the 5 sub-groups. They then describe their schooling experience using various indicators available in the Department of Education’s administrative data banks, such as age when entering junior high school and when reaching senior high school; identification as « at risk » student; rate of high school diplomation after five, six or seven years; access to junior college and rate of diplomation at that level. Finally, they explore the impact of various sociodemographic and school-related variables on the rate of high school diplomation

Analyse numérique de la convection forcée turbulente dans les tubes munis des chicanes transversales

International audienceOn présente une étude numérique du comportement dynamique et thermique d'un écoulement d'air turbulent dans un canal horizontal de section rectangulaire muni des chicanes transversales. Les équations gouvernantes, basées sur le modèle k-ε, sont résolues par la méthode des volumes finis à l'aide de l'algorithme SIMPLE. Les profils de vitesse axiale et les champs de vitesse et de température ainsi que la distribution du nombre de Nusselt sont présentés pour un cas d'exemple type

Comparative Study between Sliding Mode Control and the Vectorial Control of a Brushless doubly fed induction generator

Brushless doubly fed induction generators (BDFIG) show commercial promise forwind-power generation due to their lower capital and operational costs and higher reliability ascompared with doubly fed induction generators. This paper proposes a robust sliding mode control of grid-connected brushless doubly fed induction generator (BDFIG). The developed algorithm is based on the decoupling control by using oriented grid flux vector control strategy. The decoupling of the active and the reactive stator powers insures an optimal performance of the BDFIG at the sub-synchronous region. The stator of this machine incorporates two sets of three phase windings with different number of poles, power winding (PW) and control winding (CW). The proposed method is tested with the Matlab/Simulink software. Simulation results illustrate the performances and the feasibility of the designed control

Online Rotor Time Constant Estimator for Induction Machines with Optimum Flux

Non

Physico-Chemical and Bacteriological Qualities of Raw Milk from Collection Centers and Hawking Activity in the Rabat-Salé-Kenitra Region (Morocco)

The study aims to analyze the two circuits of the dairy chain: authorized and unauthorized, by studying the parameters influencing the physico-chemical and bacteriological quality of milk in both networks. Samples of raw milk (n=22), collected from nine collection centers (CCL): four authorized and five unauthorized in the region of Kenitra, and four hawking points in the region of Rabat, during a period between March and May 2022, were analyzed to evaluate their physicochemical and bacteriological qualities. The physicochemical quality of the milk included the measurement of chlorides, lactose and fat content, and the determination of titratable acidity and freezing point. The bacteriological quality was assessed by counting the total aerobic mesophilic flora (TAMF), total and fecal coliforms, presumed pathogenic staphylococci and searching for Salmonella. The fat content varies considerably depending on where the milk samples are collected; the average is 4.13% for licensed collection centers, versus 2.94% for unlicensed collection centers and 2.82% for hawking activity.  In terms of hygienic quality, the average bacterial load of TAMF in milk from the authorized collection centers is 3.8×108 CFU/ml. Total coliforms (TC) are present with an average rate of 9.37 ×105 CFU/ml with an average portion of 7.87 ×103 CFU/ml in fecal coliforms (FC), and 1.03 ×106 CFU/ml for presumed pathogenic staphylococci. On the other hand, milk samples from unauthorized collection centers and hawking activity showed higher levels of microbial contamination than those from licensed collection centers. Salmonella was not detected in any of the samples analyzed. The non-compliance with hygiene practices and the late application of cold during the milking, the collection, and the transportation of raw milk, partly explain the origin of this finding

Key pests and diseases of citrus trees with emphasis on root rot diseases: An overview

Citrus fruits are among the most consumed fruits in the world. However, the world production of citrus fruits is faced with several constraints which hinder its development. Furthermore, the spread of pests such as mealybugs, mites and Mediterranean fruit fly has impacted negatively on citrus quality and yield. Therefore, the main objectives of this review were to identify the key harmful organisms to the citrus crops and to highlight the appropriate methods to manage them. In this paper, more attention was given to root rot and dry root rot diseases caused by Phytophthora spp. and Fusarium spp., respectively. It was concluded that the control of citrus pests was relied on the use of chemicals. The use of integrated orchard management methods remains the best practice to minimize the adverse effects of pesticides on the environment. Two fungicides, Fosetyl-Al and Metalaxyl, were widely curatively used to control Phytophthora root rot. Moreover, the control of dry root rot disease due to Fusarium spp. requires the optimization of irrigation and fertilization inputs. In addition to the use of sanitation practices, scouting and monitoring the appearance and development of key pests and diseases help to strengthen the control methods and reduce the use of pesticides. Keywords: Citrus, pests and diseases, root rot, Phytophthora spp., Fusarium spp., integrated pest management strategy, Morocc

Isolation and Antibiotic Susceptibility of Bacteria from Otitis Media Infections in Children in Rabat Morocco

An inflammation of the middle ear by bacteria, viruses or champignons is called otitis media. The objective of this study was to determine the microbial etiology of otitis media in children in Rabat, and susceptibility pattern commonly prescribed antibiotics. Samples of ear swabs were collected from patients at the pediatric hospital, CHU Ibn Sina Rabat, during the period between February 2012 and March 2013. The total number of isolates was 67 (66 bacteria and Candida spp 1). Of these 66 bacteria spp, Streptococcus pneumoniae was the highest number (27) followed by Pseudomonas aeruginosa (16), Staphylococcus aureus (15), Escherichia coli (3), Klebsiella spp (3), Proteus species (2), and candida spp (1). This study out showed that the peak incidence was found in the age group 0-5 years (62,69%), followed by the group 5-10 years (20.90%), by cons, the group age 10-16 years was a rate of 16.41%. All bacteria were resistant to penicillin. . Pseudomonas aeruginosa, Escherichia coli and Klebsiella spp were resistant to certain antibiotics such as ofloxacin, amoxicillin, amoxicillin+clavulanic-acid, levofloxacin and cefuroxime. All strains of streptocoques pneumoniae were sensitive to ciprofloxacin, but all resistant to amoxicillin, cefuroxime and penicillin. All strains of Proteus spp were susceptible to ciprofloxacin, levofloxacin, ofloxacin, only resistant to amoxicillin. Accordingly, sufficient knowledge of the antibacterial susceptibility of bacteria, the judicious use of antibiotics and the periodic evaluation of the resistance profile of antibiotic sensitivity in the region is very important in order to avoid failure in the treatment of otitis media in children. Keywords: Otitis media, bacteria, antibacterial susceptibility, resistance, childre