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Enhanced dielectric properties of immiscible poly (vinylidene fluoride)/low density polyethylene blends by inducing multilayered and orientated structuresLin, X., Fan, L., Ren, D., Jiao, Z., Yang, W., Coates, Philip D. 03 February 2017 (has links)
Yes / In order to improve the frequency-dependent dielectric properties of the immiscible polymeric blends
which were melt-compounded by composing poly (vinylidene fluoride) (PVDF) and low density
polyethylene (LDPE), the layer multiplication and the solid phase orientation technologies were
respectively adopted as two effective strategies to optimize the dispersion state and the orientation of
internal microstructure, aiming at reducing physical porosity and improving the barrier performance
as well as crystal phase of the polymer extrudates. Results comparison showed the dielectric
properties were greatly dependent on the crystal type and the physical porosity density which were
also emphasized as the interfacial effect in the previous work [ref. 29: Lin X et al, J Appl Polym Sci
2015; 132(36), 42507]. It was found that the multilayer-structure manipulation could substantially
improve the dispersion state between the two immiscible components, enhance the mechanical
performance and reduce the internal defects and increase the dielectric constant while keeping the
dielectric loss stable. By uniaxial stretching the sample sheets at a rubber state temperature of ca.
10-20˚C below the melting point, crystal transformation was induced by increasing molecular chains
orientation degree which was also contributed to the enhancement of the dielectric properties. These
techniques implied the potential as a promising way for inducing functional structures of polymeric
blends.
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Die geometry induced heterogeneous morphology of polypropylene inside the die during die-drawing processLyu, D., Sun, Y., Thompson, Glen P., Lu, Y., Caton-Rose, Philip D., Lai, Y., Coates, Philip D., Men, Y. 21 December 2018 (has links)
Yes / The morphology distribution of isotactic-polypropylene (iPP) shaped through a die during hot stretching process was investigated via wide-angle X-ray diffraction technique. The evolution of micro-structures in the outer layer (layer closer to the die wall) and the inner layer (layer in the center of die) of die-drawn iPP were both recorded. It turned out that the difference of morphology distribution between outer and inner layers changes with the distance from the die entrance to exit. In general, a larger difference between outer and inner layers could be found at the intermediate deformation region inside the die while such difference disappeared at both of the entrance and exit regions of die. These behaviors could be interpreted as a result of the existence of a heterogeneous distribution of force field inside the die, which was caused by the die geometry and inclination of the drawing force. This work showed that the heterogeneous force field inside the die could be revealed through analyzing the morphology of a die-drawn sample.
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Predicting the location of weld line in microinjection-molded polyethylene via molecular orientation distributionLiao, T., Zhao, X., Yang, X., Whiteside, Benjamin R., Coates, Philip D., Jiang, Z., Men, Y. 31 January 2020 (has links)
Yes / The microstructure and molecular orientation distribution over both the length and the thickness of microinjection‐molded linear low‐density polyethylene with a weld line were characterized as a function of processing parameters using small‐angle X‐ray scattering and wide‐angle X‐ray diffraction techniques. The weld line was introduced via recombination of two separated melt streams with an angle of 180° to each other in injection molding. The lamellar structure was found to be related to the mold temperature strongly but the injection velocity and the melt temperature slightly. Furthermore, the distributions of molecular orientation at different molding conditions and different positions in the cross section of molded samples were derived from Hermans equation. The degree of orientation of polymeric chains and the thickness of oriented layers decrease considerably with an increase of both mold temperature and melt temperature, which could be explained by the stress relaxation of sheared chains and the reduced melt viscosity, respectively. The level of molecular orientation was found to be lowest in the weld line when varying injection velocity, mold temperature, and melt temperature, thus providing an effective means to identify the position of weld line induced by flow obstacles during injection‐molding process. / Jilin Scientific and Technological Development Program. Grant Number: 20180519001JH; National Key R&D Program of China. Grant Number: 2018YFB0704200; National Natural Science Foundation of China. Grant Numbers: 21674119, 21790342; Newton Advanced Fellowship of Royal Society. Grant Number: NA150222
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Measuring Future Time Perspective across Adulthood: Development and Evaluation of a Brief Multidimensional Questionnaire.Brothers, A., Chui, Helena, Diehl, H. 21 April 2015 (has links)
PURPOSE OF THE STUDY:
Despite calls for the consideration of future time perspective (FTP) as a multidimensional construct, mostly unidimensional measurement instruments have been used. This study had two objectives: (a) to develop a brief multidimensional questionnaire for assessing FTP in adulthood and evaluate its psychometric properties; and (b) to examine age associations and age-group differences of the dimensions of FTP.
DESIGN AND METHODS:
Data were collected from 625 community-residing adults between the ages of 18 and 93, representing young, middle-aged, and older adults. The psychometric evaluation involved exploratory factor analyses (EFA) and confirmatory FA (CFA), reliability and validity analyses, and measurement invariance testing. Zero-order and partial correlations were used to examine the association of the dimensions of FTP with age, and multivariate analysis of variance was used to examine age-group differences.
RESULTS:
EFA and CFA supported a three-factor solution: Future as Open, Future as Limited, and Future as Ambiguous. Metric measurement invariance for this factor structure was confirmed across the three age groups. Reliability and validity analyses provided evidence of sound psychometric properties of the brief questionnaire. Age was negatively associated with Future as Open and positively associated with Future as Limited. Young adults exhibited significantly greater ambiguity toward the future than middle-aged or older adults.
IMPLICATIONS:
This study provides evidence in support of the psychometric properties of a new brief multidimensional FTP scale. It also provides evidence for a pattern of age associations and age-group differences consistent with life-span developmental theory.
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Entrepreneurial orientation in dynamic environments: the moderating role of extra-organizational adviceAdomako, Samuel, Narteh, B., Danquah, Joseph K., Analoui, Farhad January 2016 (has links)
Yes / Purpose- Research on entrepreneurial orientation (EO) has concluded a positive link between
EO and firm performance and that relationship depends on several contingencies. The paper
derives insights from the absorptive capacity and contingency perspectives to introduce extraorganizational advice as a moderator of the relationship between EO and firm performance in a dynamic environment.
Design/methodology/approach-Using survey data from 340 small and medium-sized
enterprises (SMEs) in Ghana, the study examines the moderating influence of extraorganizational advice on the EO-firm performance relationship in dynamic environments.
Findings-The study’s empirical findings suggest that extra-organizational advice amplifies
the EO-performance relationship in dynamic environments.
Research limitations/implications-The cross-sectional design of the study does not permit
causal inferences to be made regarding the variables examined. Future studies may use
longitudinal design to examine the causal links of the variables. Limitations aside, the study
helps to answer how extra-organizational advice translates EO into improved performance in
an environment characterised by constant flux.
Practical implications- The results of this paper can assist entrepreneurs and policy-makers
in understanding the dynamics and processes involved in implementing a strategic orientation
to achieve higher performance. For SME managers, firm performance is determined by high
levels of EO and extra-organizational advice in dynamic environments. The understanding of
this issue can promote the development and maintenance of entrepreneurial ventures.
Originality/value-The paper examines an important, but under-researched issue-the
moderating effect of extra-organizational advice on the EO-performance relationship in
dynamic environments. To the best of the authors’ knowledge, the present study pioneers
research in this area.
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Entrepreneurial Orientation, Entrepreneurial Intent and New Venture Creation: Test of a Framework in a Chinese ContextWu, Jinpei 21 July 2009 (has links)
The empirical evidence is rather weak and sometimes inconsistent as to what predicts an individual's decision to start a business. Among many possible causes, this study attempts to disentangle the effects of individual differences and context. I propose to use a framework involving an individual's entrepreneurial intent, entrepreneurial orientation and four individual difference factors as a means to isolate individual difference determinants of entrepreneurial intent. These are captured in new construct called entrepreneurial orientation. Samples of entrepreneurs and college students from the United States and China were used to test the relationships. The empirical results show that entrepreneurial orientation is positively related to individual differences factors and entrepreneurial intent. Even more, it fully or partially mediates the relationships between the individual differences and entrepreneurial intent. Among the four individual differences listed, opportunity recognition seems to be the best predictor of an individual's entrepreneurial orientation and entrepreneurial intent. Future research should further examine opportunity recognition and entrepreneurial orientation. It appears that attempting to isolate effects of individual differences from context can be a viable strategy for studying determinants of new venture creation. / Ph. D.
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The Manufacture and Mechanical Properties of Poly(ethylene terephthalate) Fibers Filled with Organically-Modified MontmorilloniteLitchfield, David W. 27 May 2008 (has links)
This work is concerned with mechanical property improvements to poly(ethylene terephthalate), PET, fibers by the addition of layered silicate nanoparticles and by drawing the un-oriented nanocomposite filaments in a second step. No previous studies on PET fibers filled with montmorillonite (MMT) nanoclay examined fiber drawability at temperatures above the glass transition. Therefore, the primary objective of this research was to determine 1) if PET nanocomposite fibers could be drawn to finer diameters and 2) whether drawing imparted improved Young's modulus and tenacity (i.e. strength) relative to un-filled PET fibers. Of equal importance to this work, the subsequent objective was to discern and understand the role of nanoclay in 1) the production of improved or reduced mechanical properties and 2) the ability to draw PET to lower or higher than normal draw ratios.
In the first part of this thesis, the improvements in Young's modulus and tenacity of PET fibers filled with various types of organically modified montmorillonite is shown and the method to produce them is discussed. Greater improvements in mechanical properties occurred when the MMT stacks were intercalated with PET. A nominal 1 wt% loading of dimethyl-dehydrogenated tallow quaternary ammonium surface modified MMT in drawn PET fiber showed a 28% and 63% increase in Young's modulus and strength, respectively. Relative to an un-filled PET fiber, these results exceeded the upper-bound of the rule of mixtures estimate. Therefore, both the type of surface modification and concentration of MMT were shown to affect the degree of PET orientation and crystallinity. Furthermore, drawability above Tg and elongation-at-break increased upon the addition of organically modified MMT to un-oriented PET fibers, which was a key distinction of this work from others examining similar systems.
Interestingly, the mechanical properties of modulus and tenacity showed a maximum with concentration of alkyl modified clay, but drawability did not show significant variation with increasing nanoclay content. Thermal analysis and Raman spectroscopy was used to examine the role of nanoclay in creating this maximum in mechanical properties. At low loadings, nanoclay was shown to intercalate with PET and enhance amorphous orientation. At higher concentrations of nanoclay the presence of large agglomerates prevented efficient orientation to the fiber axis and acted as stress concentrators to aid in cavitation and failure during testing. Raman spectroscopy showed that the as-spun unfilled PET fibers possessed significantly more trans conformer content of the ethylene glycol moiety than the nanocomposite fibers. The greater gauche content of the nanocomposite fibers delayed crystalline development during non-isothermal DSC scans to higher temperatures was associated with the increased drawability. / Ph. D.
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Usages des contenus numériques en orientation scolaire et professionnelle auprès des élèves du secondaireVilleneuve, Nadya 17 January 2020 (has links)
Plusieurs spécialistes de l’orientation interviennent auprès d’une population adolescente, caractérisée par son utilisation multiple et fréquente d’Internet et des médias sociaux (Thoër et Millerand, 2017; CEFRIO, 2017). Or, quoique les sites web et Facebook des écoles offrent un environnement scolaire numérique avec des possibilités pour l’orientation scolaire et professionnelle (OSP) auprès des jeunes, leur usage reste à ce jour relativement peu documenté. Notre recherche s’intéresse aux usages numériques en OSP en milieu scolaire. Autant le rôle de l’OSP au sein du Programme de formation de l’école québécoise (OCCOQ, 2013; MELS, 2007) que l’influence des interactions communautaires dans les intentions d’avenir des jeunes (Law, 1981) servent de cadre de référence pour comprendre ces usages. L’objectif principal de cette recherche qualitative est d’explorer les usages des sites web et Facebook en OSP au sein d’une commission scolaire francophone et de ses établissements d’enseignement secondaire au Québec. Treize sites web (547 éléments web) et treize sites Facebook (1531 publications) d’une commission scolaire ont fait l’objet d’une analyse documentaire rigoureuse. Les résultats de la recherche indiquent que, pour les sites web et les sites Facebook, l’OSP se fait rare, sous-exploite les possibilités qu’offrent les sites, vise une population principalement adulte et offre très peu de visibilité. Les analyses permettent de dégager trois principaux constats : l’OSP tirerait profit à occuper l’environnement numérique scolaire auprès des jeunes, les formateurs auraient avantage à offrir de l’accompagnement aux professionnels de l’orientation et les spécialistes de l’orientation auraient intérêt à adopter une posture éclairée devant l’usage du numérique. / Many school counsellors work with a youth population that makes varied and frequent use of the internet and social media (Thoër & Millerand, 2017; CEFRIO, 2017). Although web sites and Facebook available in schools offer young people a digital environment with possibilities for educational and career development (ECD), their utilization is not yet widely documented. Our research interest is the use of digital resources for ECD in the school environment. The role of ECD in the Quebec school system’s program of education (OCCOQ, 2013; MELS, 2007) as well as the influence of community interactions on young people’s plans for their future (Law, 1981) serve as terms of reference for understanding their use. The main objective of this qualitative research is to explore the use of web sites and Facebook for ECD in secondary schools in a Quebec French school board. Thirteen web sites (547 web elements) and thirteen Facebook sites (1531 publications) from one school board were the subject of a rigorous documentary analysis. The results of this research indicate that ECD is rare on websites and Facebook sites, that it underutilizes the potential of the sites, that it is directed mainly towards an adult population and that it has very little visibility. The analysis provides three main findings: ECD would benefit from occupying the digital environment available to young people, training should be available to accompany guidance professionals in their use of digital media and school counsellors should adopt a positive posture towards these methods and towards the digital environment.
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Une étude sur la cohérence pédagogique : une recherche expérientielleRioux, Madeleine 25 April 2018 (has links)
Québec Université Laval, Bibliothèque 2015
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La coiffure : un passage culturel?Lavoie, Christine 20 April 2018 (has links)
Que la culture soit identifiée comme étant un tout représentant l'humain, son oeuvre et sa manière d'habiter le monde ou encore qu'elle soit une référence au développement des facultés de l'esprit, elle se présente sous diverses définitions que nous parvenons difficilement à accoler aux métiers de la formation professionnelle. L'exercice semble tout aussi hasardeux lorsque nous essayons de la faire émerger de la pratique éducative d'un enseignant, tel celui de la coiffure, de qui il est attendu d'être un « passeur de culture » (M.E.Q., 2001). Dans ce mémoire, une quête d'identification d'éléments culturels portés par les enseignants et les artisans du métier de la coiffure, nous explicitons la typologie des métiers proposée par (Gagnon, 2010a), qui notamment distingue les orientations traditionnelle et technoscientifique susceptibles de se retrouver dans un métier donné, et nous proposons des indicateurs de ces éléments. Nous expliquons ensuite cette typologie au domaine de la coiffure conduisant à l'illustration des quatre cultures-types sous-tendues par la typologie. Il devient alors possible de mieux comprendre cette culture implicite de la coiffure, qui vit dans l'ombre, sans porter de mots, sans être objet de formation explicite.
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