Analyzing arithmetic word problem solving difficulties in middle school students

International audienceIn this article, we study the performance of students in early sixth and seventh grade in a wide range of arithmetic or logical problems. By means of socio-demographic indexes and tests measuring abilities that are either general (language, short-term memory, etc.) or specifically related to the digital domain, we try to identify the variables with or without a significant contribution to the problem solving scores and to determine their relative weights.The sample consists of 269 middle school students (129 in the 6th and 140 in the 7th year), enrolled in public or private schools, selected to reflect a diversity of social and geographical contexts. The results of multiple hierarchical regression highlight the importance at this level of specifically mathematical knowledge more than that of general abilities or even demographic dimensions.Cet article se propose d’étudier les performances d’élèves scolarisés au début du collège (en sixième et cinquième) à une large série de problèmes arithmétiques ou logiques. Par le biais d’indices socio-démographiques et d’épreuves testant des capacités soit générales (langage, mémoire à court terme, etc.) soit spécifiquement liées au domaine numérique, il cherche à identifier les variables ayant ou non une contribution significative sur les scores en résolution de problèmes et à déterminer leurs poids relatifs.L’échantillon est constitué de 269 collégiens (129 en 6e et 140 en 5e), scolarisés dans des établissements scolaires, publics ou privés, choisis pour rendre compte d’une diversité de contextes sociaux ainsi que géographiques. Les résultats de la régression multiple hiérarchique mettent en évidence l’importance à ce niveau des savoirs et savoir-faire spécifiquement mathématiques, plus que celle des capacités générales ou des dimensions démographiques

Experimental and theoretical studies for mild steel corrosion inhibition in 1.0 M HCl by three new quinoxalinone derivatives

Three quinoxalinone derivatives, namely (E)-3-styrylquinoxalin-2(1H)-one (SQ), (E)-3-(4methoxystyryl)quinoxalin-2(1H)-one (MOSQ) and (E)-3-(4-methoxystyry1)-7-methylquinoxalin-2(1H)-one (MOSMQ) were synthesized and characterized. Thus, their inhibition effects on mild steel corrosion in 1.0 M HCl medium were investigated using weight loss method, electrochemical measurements. The effect of temperature on the corrosion behavior of mild steel was studied in the range of 298-328 K. Polarization measurements indicated that, the studied compounds act as a mixed type inhibitors, the inhibition efficiency depends on their concentrations and followed the order MOSQ> MOSMQ> SQ Electrochemical impedance spectroscopy showed that all compounds act by the formation of a protective film at the metallic surface. The adsorption of three inhibitors on steel surface obeyed Langmuir model, thus the thermodynamic and kinetic parameters were calculated and discussed. In the part based on DFF calculations of this study, some electronic properties of studied molecules were calculated and discussed with the help of B3LYP/6-311G (d,p), B3LYP/6-311 ++G (d,p) and B3LYP/6-311G ++ (2d,2p) methods. The theoretical and experimental results are in good agreement. (C) 2016 Elsevier B.V. All rights.reserved.Three quinoxalinone derivatives, namely (E)-3-styrylquinoxalin-2(1H)- one (SQ), (E)-3- (4-methoxystyryl)quinoxalin-2(1H)- one (MOSQ) and (E)-3- (4-methoxystyryl)- 7-methylquinoxalin-2(1H)- one (MOSMQ) were synthesized and characterized. Thus, their&nbsp;inhibition effects on mild steel corrosion in 1.0 M HCl medium were investigated using weight&nbsp;loss method, electrochemical measurements. The effect of temperature on the corrosion&nbsp;behavior of mild steel was studied in the range of 298-328 K. Polarization measurements&nbsp;indicated that, the studied compounds act as a mixed type inhibitors, the inhibition efficiency&nbsp;depends on their concentrations and followed the order MOSQ &amp;gt; MOSMQ &amp;gt; SQ.&nbsp;Electrochemical impedance spectroscopy showed that all compounds act by the formation of a&nbsp;protective film at the metallic surface. The adsorption of three inhibitors on steel surface&nbsp;obeyed Langmuir model, thus the thermodynamic and kinetic parameters were calculated and&nbsp;discussed. In the part based on DFT calculations of this study, some electronic properties of&nbsp;studied molecules were calculated and discussed with the help of B3LYP/6-311G (d,p),&nbsp;B3LYP/6-311++G (d,p) and B3LYP/6-311G++ (2d,2p) methods. The theoretical and&nbsp;experimental results are in good agreement.</p