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Use of Polymeric Compatibilizers in Polypropylene/Calcium Carbonate Composites
Tucker, J . David,Lear, Patricia L .,Atkinson, Gregory S .,Lee, Sung Gyu,Lee, Seung Jong 한국화학공학회 2000 Korean Journal of Chemical Engineering Vol.17 No.5
The effects of compatibilizing agents on the mechanical properties, viscoelastic properties, and morphology of polypropylene filled with calcium carbonate composites are investigated. It is found that the use of PP-g-MA and PP-g-AA significantly increases the tensile strength and improves particle dispersion and interfacial adhesion. The higher effect of compatibilization is obtained by using PP-g-MA as a compatibilizer. The results on the dynamic thermomechanical properties, viscoelastic properties, and SEM pictures also support the improved interfacial characteristics. It is also found that there exists a limiting amount of PP-g-MA at about 5% beyond which a further increase in the tensile strength is not obtained. The use of untreated calcium carbonate or SEBS-g-MA does not allow films to be drawn for the purpose of testing.
Global measures of distributive mixing and their behavior in chaotic flows
Tucker, Charles L.,Peters, Gerrit W.M. The Korean Society of Rheology 2003 Korea-Australia rheology journal Vol.15 No.4
Two measures of distributive mixing are examined: the standard deviation $\sigma$ and the maximum error E, among average concentrations of finite-sized samples. Curves of E versus sample size L are easily interpreted in terms of the size and intensity of the worst flaw in the mixture. E(L) is sensitive to the size of this flaw, regardless of the overall size of the mixture. The measures are used to study distributive mixing for time-periodic flows in a rectangular cavity, using the mapping method. Globally chaotic flows display a well-defined asymptotic behavior: E and $\sigma$ decrease exponentially with time, and the curves of E(L) and $\sigma$ (L) achieve a self-similar shape. This behavior is independent of the initial configuration of the fluids. Flows with large islands do not show self-similarity, and the final mixing result is strongly dependent on the initial fluid configuration.
Facebooking in Distance Education: Constructing Virtual Communities of Practice
Virginia Tucker 충북대학교 교육개발연구소 2013 한국교육논총 Vol.34 No.1
The growth of distance education warrants a closer look at how virtual communities of practice form in asynchronous online classrooms. Prior studies have sought to identify a process to virtual community formation, which may vary depending upon the media used for collaboration. This microstudy examines how one student group in a distance writing course used the popular social media site Facebook to construct community and whether the stages of virtual community development were observed in this setting. Findings suggest that revisions might be made to our current understanding of the process of building virtual community within small groups. “Othering” and social norming should be considered as an important step in the group’s progress toward a co-identity and knowledge-sharing community. The construction of social norms is so important to group co-identity that it transgresses the established norms of communicating through Facebook. Further, the use of a social media site for group communication may encourage social interaction and cyber-play among the group, to either the detriment of work-related discourse or benefit of friendship-making. Further, the process of virtual community formation is largely iterative where the quality of discourse depends on the nature of group tasks rather than time.
The Study on the Motivation of Sex-Selective Abortion among Indian Immigrants in U.S.A
Jill Tucker,Sung Seek Moon,Minkyung Kim,KyungSook Kim 보안공학연구지원센터 2015 International Journal of Bio-Science and Bio-Techn Vol.7 No.3
This qualitative study sought to explore the motivations behind sex-selective abortion among Indian immigrants in the United States. Using a theoretical framework incorporating social learning theory and self-determination theory, the research design consisted of semi-structured interviews of 20 married Indian immigrant women. Based on an analysis of these interviews, the following emergent themes were discovered: The extrinsic motivation was “Money”, “Education (lack of)”, “Familial Pressure”, and the introjected motivation was “Problems for and from Girls”, “Dowry”, “Familial Preference”, and identified motivation was “Familial Ties”, “Inheritance”, “Son’s Duty”, “Name Carried Forward”, and the intrinsic motivation was “Want a Boy”. Theoretical and social work practice implications based on the findings of the study were discussed. Based on the researcher’s findings, there remains a great deal of opportunity for future studies to provide more insight into this phenomenon. Beyond researching this specific issue, the researcher recommends a continued focus on women’s rights issues within the United States.