1,720,977 research outputs found
Effect of diblock copolymers on morphology and mechanical properties for syndiotactic polystyrene/ethylene-propylene copolymer blends
No full textInterfacial agents are often used to compatibilize immiscible polymer blends. They are known to reduce the interfacial tension, homogenize the morphology, and improve adhesion between phases. In this study, two diblock copolymers of styrene/ethylene-propylene (SEP), which have different molecular weights, were used to compatibilize a blend of syndiotactic polystyrene (sPS) 75% and ethylene-propylene rubber (EPR) 25% so as to extend the applications of sPS as incoming thermoplastics. The morphological analysis and emulsification curve, which relates the average size of the dispersion particles to the concentration of diblock copolymers added, was used to investigate the efficiency of the interfacial agents on the blend morphology. A notched izod impact test and a tensile test were also performed to determine the compatibilization effect of different molecular weight copolymers on the mechanical properties of the blends and to establish links between morphology and mechanical properties. Results suggest that the lower molecular weight diblock copolymer showed an effective emulsifying capacity for sPS/ERP immiscible blend in morphology and mechanical properties. (C) 2004 Wiley Periodicals, Inc
REAL-TIME ACCELEROMETER SIGNAL PROCESSING OF END POINT DETECTION AND FEATURE EXTRACTION FOR MOTION DETECTION
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The fabrication of syndiotactic polystyrene/organophilic clay nanocomposites and their properties
No full textThe fabrication of nanocomposite of syndiotactic polystyrene (sPS)/organophilic clay was conducted by melt intercalation. To avoid the decrease of interlayer spacing due to desorption of organic materials at high temperature, various amorphous styrenic polymers were introduced during the melt mixing process. The nanocomposites were fabricated via two different methods, one is the stepwise mixing method, which is the melt intercalation of amorphous styrenic polymers into organophilic clay followed by blending with sPS, and the other is the simultaneous mixing method, in which all components are melt mixed together. The microstructures of nanocomposites were investigated by X-ray diffraction (XRD) and transmission electron microscopy. The mechanical properties of the nanocomposites such as tensile strength, flexural modulus and izod impact strength were measured and discussed in relation to their microstructures. Both fabrication methods yielded the nanocomposites with different microstructures ranging from intercalated structure to exfoliated structure depending on the kind of amorphous styrenic polymers, which was revealed by the increase in interlayer spacing on X-ray spectrum. Amorphous polymers intercalated into the clay gallery previously is considered to play an important role in maintaining the intercalated or exfoliated structure without any contraction of interlayer spacing even at sPS melting temperature. The fabrication method also influenced the microstructure and mechanical properties, especially tensile strength. In the case of nanocomposites having intercalation structure, the stepwise mixing method yielded more obvious intercalation structure than the simultaneous mixing method so that the former method resulted in higher tensile strength. On the other hand, the nanocomposite having exfoliated structure showed similar mechanical properties between the two fabrication methods. (C) 2001 Published by Elsevier Science Ltd
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Preparation and characterization of syndiotactic polystyrene/ethylene‐propylene copolymer blends
No full textThe reactive compatibilization of syndiotactic polystyrene (sPS)/oxazolinestyrene copolymer (RPS)/maleic anhydride grafted ethylene-propylene copolymer (EPR-MA) blends is investigated in this study. First, the miscibility of sPS/RPS blends is examined by thermal analysis. The cold crystallization peak (T-cc) moved toward higher temperature with increased PRS, and, concerning enthalpy relaxation behaviors, only a single enthalpy relation peak was found in all aged samples. These results indicate that the sPS/RPS blend is miscible along the various compositions and RPS can be used in the reactive compatibilization of sPS/RPS/EPR-MA blends. The reactive compatibilized sPS/RPS/EPR-MA blends showed finer morphology than sPS/EPR-MA physical blends and higher storage modulus (G') and complex viscosity (eta*) when RPS contents were increased. Moreover, the impact strength of sPS/RPS/EPR-MA increased significantly compared to sPS/EPR-MA blend, and SEM micrographs after impact testing show that the sPS/RPS/EPR-MA blend has better adhesion between the sPS matrix and the dispersed EPR-MA phase. (C) 2002 Wiley Periodicals, Inc
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Synthesis and material properties of syndiotactic polystyrene/organophilic clay nanocomposites
No full textSyndiotactic polystyrene (sPS)/organophilic clay nanocomposites were fabricated by direct-melt intercalation method. To overcome the thermal instability of organophilic clay at high-melt processing temperatures of sPS, an organophilic clay modified by alkyl phosphonium was adopted, which is known to be thermally stable. By using the newly synthesized clay, we could fabricate sPS intercalated nanocomposites. The microstructures of nanocomposites were confirmed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The crystallization rate of nanocomposites investigated by differential scanning calorimetry (DSC) does not increase despite the presence of clay, which may be due to the physical hindrance of organic modifiers in the clay dispersion. Nanocomposites exhibited enhanced mechanical properties such as strength and stiffness relative to the virgin polymer. In addition, thermal stability was confirmed to be improved by thermogravimetric analysis (TGA). (C) 2004 Wiley Periodicals, Inc
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