Influence of numerical and viscous dissipation on shock wave reflections in supersonic steady flows

Numerical simulations are investigated to describe precisely the shock wave reflections in supersonic steady air flow field. The main objectives are to study the influence of the wedge trailing edge corner angle, of the numerical methods and of the viscous effects on the shock wave reflections and on the hysteresis behavior. The computations are done with different MUSCL-TVD finite volume schemes and the corresponding results are compared. The flow viscosity is also taken into account and comparisons are made between inviscid and viscous flow simulations. The results display the non-negligible influence of the numerical scheme accuracy on the results, mainly on the position and height of the Mach stem, and the relatively weak influence of the flow viscosity on these parameters. Comparisons between numerical results and experimental data have also been done and a good agreement is only observed for small wedge angles mainly due to the three-dimensional effects in the experimental setup.     

Coverage-biased random exploration of large models and application to testing

This paper presents several randomised algorithms for generating paths in large models according to a given coverage criterion. Using methods for counting combinatorial structures, these algorithms can efficiently explore very large models, based on a graphical representation by an automaton or by a product of several automata. This new approach can be applied to random exploration in order to optimise path coverage and can be generalised to take into account other coverage criteria, via the definition of a notion of randomised coverage satisfaction. Our main contributions are a method for drawing paths uniformly at random in composed models, i.e. models that are given as products of automata, first without and then with synchronisation; a new efficient approach to draw paths at random taking into account some other coverage criterion. Experimental results show promising agreement with theoretical predictions and significant improvement over previous randomised approaches. This work opens new perspectives for future studies of statistical testing and model checking, mainly to fight the combinatorial explosion problem.     

Factors influencing encapsulation behavior in composite droplet-type polymer blends

In this study the influence of the molecular weight of the dispersed phase components on encapsulation effects in the composite droplet phase was examined for high density polyethylene (HDPE)/PS/PMMA ternary blends. Three different blends composed of various PS and PMMA materials dispersed in an HDPE matrix were prepared using an internal mixer. The morphology was studied by light and electron microscopy. Current models used for predicting encapsulation effects and composite droplet formation in ternary systems (based on static interfacial tension) predict in all cases that PS will encapsulate the PMMA. However, in one case, an unexpected encapsulation of PS by PMMA was observed. It was found that arguments based on the effect of viscosity ratio or the absolute viscosity of the different dispersed phases do not explain that discrepancy. In addition, the reversal of that latter composite droplet morphology from PMMA encapsulating PS to PS encapsulating PMMA was observed upon annealing treatment. Considering all the above, a conceptual model was developed to predict encapsulation effects in composite droplet type systems based on the use of a dynamic interfacial tension (i.e. taking into account the elasticity of the polymer components). Calculations based on the dynamic interfacial tension model, using elasticities based on constant shear stress, were able to account for all of the observed encapsulation effects in this study.     

Cell structure and dynamic properties of injection molded polypropylene foams

The cell structure and properties of branched and linear polypropylene (PP) foams containing organically modified nanoclay and maleic anhydride grafted polypropylene (PPMA) have been thoroughly investigated. X-ray diffraction (XRD) and melt rheometry were used to identify the structure and linear viscoelastic properties of the nanocomposites, as well as the effectiveness of two different compatibilizers. These nanocomposites were used in injection molding to investigate their foamability and the influence of experimental conditions such as chemical foaming agent concentration, shot size, back pressure, injection speed, as well as melt temperature and different injection methods on the resulting cell structure of the foams. Quite different results were obtained with the linear and the branched PP. While the foamability of the branched PP was intrinsically good, that of the linear one could largely be improved by modifying its rheological properties and favoring nucleation through the addition of nanoclay. The effect of cell structure on the dynamic mechanical properties of the foams was also investigated using dynamic mechanical analysis (DMA). POLYM. ENG. SCI., 47:1070–1081, 2007. © 2007 Society of Plastics Engineers     

Enriching our theoretical repertoire: the role of evolutionary psychology in technology acceptance

Information systems (IS) research has drawn heavily on social and cognitive psychology to explain technology adoption. Indeed, the many variations of the technology acceptance model all share these same theoretical foundations. Focusing exclusively on the socio-cognitive lens can lead to overlooking enhanced explanations of technology acceptance, such that new theoretical perspectives may be warranted. In this qualitative grounded theory study, we discovered how the lens of evolutionary psychology, as embodied in the Four-Drive model, was helpful in understanding technology acceptance across three organizational sites. We contend that evolutionary psychology is an important addition to the theoretical repertoire of IS researchers, and propose including ‘evolved psychological mechanisms’ within traditional models of technology acceptance.     

Validation chez les adolescents d'une version francophone d'un instrument de mesure de la peur du jugement négatif d'autrui.

The popularity of the Fear of Negative Evaluation scale (FNE; Watson & Friend, 1969) stems from the centrality of this construct in personality, social and clinical psychology. In order to meet the needs of the Francophone researchers community, Kéroack, Boisvert, and Prévost (1987) traduced the short version of this instrument. Since social anxiety is most salient in adolescence, there is a need for normative and psychometric data for this population. This research aims at documenting the psychometric properties and norms for Francophone adolescents. Five hundred and seventy-eight participants aged from 14 to 19 years completed the French versions of the short FNE and the Social Avoidance and Distress scale. The factorial structure, the internal consistency and the convergent validity analyses confirm the traduction's quality and the questionnaire's validity. Norms are presented separately for females and males. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

PEM: The small company-dedicated software process quality evaluation method combining CMMISM and ISO/IEC 14598

Many small software organizations have recognized the need to improve their software product. Evaluating the software product alone seems insufficient since it is known that its quality is largely dependant on the process that is used to create it. Thus, small organizations are asking for evaluation of their software processes and products. The ISO/IEC 14598-5 standard is already used as a methodology basis for evaluating software products. This article explores how it can be combined with the CMMI to produce a methodology that can be tailored for process evaluation in order to improve their software processes. ^SM: CMMI is a service mark of Carnegie-Mellon University. Sylvie Trudel has over 20 years of experience in software. She worked for more than 10 years in development and implementation of management information systems and embedded real-time systems. Since 1996, she works as a process improvement specialist, implementing best practices into organizations processes from CMM and CMMI models. She performed several CMM and CMMI assessments and participated in many other CMM assessments such as CBA IPI, SCE, and other proprietary methods. She obtained a bachelors degree in computer science in 1986 from Laval University in Québec City and a Masters degree in Software Engineering at école de Technologie Supérieure (éTS) in Montréal. Sylvie is currently working as a software engineering advisor at the Centre de Recherche Informatique de Montréal (CRIM). Jean-Marc Lavoie has been working in software development for over 10 years. He performed and published a comparative study between the guide to the SWEBOK and the CMMI in 2003. Jean-Marc obtained a bachelor degree in Electrical Engineering. He is pursuing a Masters degree in Software Engineering at école de Technologie Supérieure (éTS) in Montréal while working as a software architect at Trisotech. Marie-Claude Pare has been working in software development for 7 years. Marie-Claude obtained a bachelor degree in Software Engineering from école Polytechnique in Montréal. She is pursuing a Masters degree in Software Engineering at école de Technologie Supérieure (éTS) in Montréal while working as a software engineer at Motorola GSG Canada. Dr Witold Suryn is a Professor at the école de technologie supérieure, Montreal, Canada (engineering school of the Université du Québec network of institutions) where he teaches graduate and undergraduate software engineering courses and conducts research in the domain of software quality engineering, software engineering body of knowledge and software engineering fundamental principles. Dr Suryn is also the principal researcher and the director of GELOG : IQUAL, the Software Quality Engineering Research Group at école de technologie supérieure. From October 2003 Dr. Suryn holds the position of the International Secretary of ISO/IEC SC7 – System and Software Engineering.     

Solid-solution partitioning of Cd, Cu, Ni, Pb, and Zn in the organic horizons of a forest soil

We report the solid-liquid partitioning of Cd, Cu, Ni, Pb, and Zn in 60 organic horizon samples of forest soils from the Hermine Watershed (St-Hippolyte, PQ, Canada). The mean Kd values are respectively 1132, 966, 802, 3337 and 561. Comparison of those Kd coefficients to published compilation values show that the Kd values are lower in acidic organic soil horizons relative to the overall mean Kd values compiled for mineral soils. But, once normalized to a mean pH of 4.4, the Kd values in organic soil horizons demonstrate the high sorption affinity of organic matter, which is either as good as or up to 30 times higher than mineral soil materials for sorbing trace metals. Regression analysis shows that, within our data set, pH and total metal contents are not consistent predictors of metal partitioning. Indeed, metal sorption by the solid phase must be studied in relation to complexation by dissolved organic ligands, and both processes may sometime counteract one another.     

Facteurs associés aux problèmes de comportement intériorisés et extériorisés chez des adolescentes agressées sexuellement.

The present study investigated the associated factors of internalising and externalising behaviour problems among sexually abused adolescents. One hundred fifty-eight female adolescent victims of sexual abuse, aged between 13 and 17 years, were recruited. Participants completed a battery of questionnaires measuring cognitive distortions, coping strategies, empowerment, behaviour problems, perception of their relationship with their mother and father, maternal support, characteristics of the sexual abuse as well as other forms of violence experienced. Results show that interpersonal distrust and general self-attributions of blame are two factors associated with both internalising and externalising behaviour problems. In addition, the mother/daughter relationship is associated with externalising behaviour problems. These results partially support Spaccarelli's model. They also highlight the important role of cognitive distortions, particularly general self-attributions of blame and interpersonal distrust, which may be targeted in treatments that are aimed at reducing behavioural problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of built environment on pedestrian's crossing decision

The objective of this experimental study is to identify the differentiation made by pedestrians, in their crossing decision, between various urban environments, notably in terms of perception of walking pleasantness and safety. This experiment further aims to identify the environmental features that pedestrians take into account and the inferences they develop and use to explain their road crossing decision. Sets of photographs presenting five different environments (city center, inner suburbs, public housing in the outskirts, commercial zone in the outskirts and countryside) were presented to 77 participants divided up into three age groups (pre-adolescents, young and middle adults). Their decision to cross or not, their perception of pleasantness and safety, and the elements they take into account to make a decision were collected for each environment presented. The quantitative results show the pedestrians’ perceptions of the pleasantness and safety of public spaces, in terms of walking, largely vary with urban environments. Moreover, the crossing decision significantly varies according to the environment. Pedestrians were significantly more inclined to take the decision to cross in city center than in the other sites presented. The qualitative analysis of the interviews shows that the presence and function of the buildings, the quality of the sidewalks and the marked parking spaces are key factors to explain their crossing decision, by enabling them to infer the density of pedestrians and traffic and the vehicle speed.