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排序方式: 共有1180条查询结果,搜索用时 15 毫秒
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Gabriela Pitolli Lyra Valdemir Santos Eliria Maria de Jesus Agnolon Pallone Ruth Herta Goldschmidt Aliaga Kiminami Bruno Carlos De Santis João Adriano Rossignolo 《International Journal of Applied Ceramic Technology》2021,18(3):705-715
This work aimed to examine the performance of the hybrid sintering of clay ceramic in a microwave furnace, compared to the sintering process in a conventional furnace. The raw materials were subjected to X-ray fluorescence, loss on ignition (LOI), X-ray diffraction, particle size distribution, real specific mass, and thermogravimetric analyses. The red clay ceramic mass was prepared, extruded, pre-sintered in a conventional furnace at 600°C/60 min, and sintered at temperatures between 700 °C and 1100 °C. The sintering conventional (resistive oven) was carried out for 60 min with a heating rate of 10°C/min. In the microwave furnace, the sintering times were 5, 10, and 15 min, with a heating rate of 50°C/min, with a sintering chamber coated with silicon carbide (susceptor). The sintered specimens were characterized according to linear shrinkage, water absorption, apparent porosity, apparent specific mass, X-ray diffraction, Raman spectroscopy analysis, spectroscopy analysis in the ultraviolet and visible regions, microhardness, and scanning electron microscopy. The results showed that microwave sintering promoted an increase in the microhardness and apparent specific mass, and reduction in water absorption and apparent porosity values, due to greater densification in the microstructure. The best results occurred for specimens sintered at 1100°C. 相似文献
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A Avraméas D McIlroy A Hosmalin B Autran P Debré M Monsigny AC Roche P Midoux 《Canadian Metallurgical Quarterly》1996,26(2):394-400
Dendritic cells (CD) are the most efficient antigen presenting cells for T lymphocytes. CD1a+ CD14- CD with high antigen-presenting capacities can now be obtained easily from adherent peripheral blood monocytes by culture in the presence of granulocyte/macrophage colony-stimulating factor and interleukin-4 (Sallusto et al., J. Exp. Med. 1994. 179: 1109). Human macrophages express a membrane lectin, or sugar-specific receptor, which specifically mediates the binding and endocytosis of mannose- and fucose-terminated glycoproteins and is involved in the phagocytosis of pathogens. A similar lectin activity was sought on cultured human DC using flow cytometry and confocal microscopy to detect binding and internalization of fluoresceinated neoglycoproteins [bovine serum albumin (BSA) substituted with sugar residues]. Several neoglycoproteins, especially alpha-L-fucosyl-, alpha-D-mannosyl-, N,N'-di-acetyl-beta-chitobiosyl- and beta-D-glucosyl-BSA, were endocytosed by cultured human CD1a+ DC as well as by CD1a- CD14- cells which were also obtained in the culture. Fuc-BSA and Man-BSA had the same number of binding sites (1.7 x 10(6)/cell) on CD1a+ DC, and bound with an affinity constant close to 10(7) 1/mol. Inhibition experiments indicated that these two neoglycoproteins bound to the same membrane lectin. CD1a+ and CD1a- cells were both labeled by an antiserum specific for the human macrophage mannose receptor. The membrane lectin specific for mannose and fucose that is evidenced in these experiments on cultured DC may be similar to the macrophage membrane lectin or may share functional and structural properties with it. 相似文献
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Hans-Joachim Kleebe Gabriela Hilz Günter Ziegler 《Journal of the American Ceramic Society》1996,79(10):2592-2600
Sol-gel-derived mullite ceramics were processed by pressureless sintering at 1600°, 1650°, and 1700°C for 4 h. Microstructural and microchemical characterization of the mullite materials was performed using transmission electron microscopy, in conjunction with energy-dispersive X-ray spectroscopy and electron energy-loss spectroscopy (EELS). Apart from mullite grain diameter and triplepocket size, no major microstructural changes were observed with increasing sintering temperature. Residual glass was present at triple pockets and along two-grain junctions. Not all grain boundaries revealed the presence of a continuous amorphous intergranular film. Clean interfaces were observed only at boundaries with one grain parallel to the [001] orientation (low-energy configuration). Quantitative EELS analysis of mullite grains and glass pockets revealed only small changes in composition with increasing sintering temperature; i.e., the alumina:silica ratio slightly increased for mullite and glass. The analysis implied that mullite with this relatively high aluminum content would not be stable adjacent to residual glass. However, a stable glass-mullite system has been proposed, because impurity cations were detected within glass pockets, which suggested a slight shift of the subsolidus line (glass-mullite/ mullite) to a higher amount of alumina. Energy-loss nearedge structure studies of the Si- L 2,3 edge revealed a similar near-edge structure for the mullite, residual glass, and quartz. Thus, SiO4 tetrahedra were thought to be the main building units of the glass contained in sintered mullite. 相似文献
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New polyimides containing 4,4′‐bipyridinium units were synthesized by the reaction of bis(dichloromaleimide)arylene derivatives with 4,4′‐bipyridine in meta‐cresol. IR and 1H‐NMR spectroscopy and elemental analysis as well confirmed their structures. The polymers were characterized by viscometric measurements, softening points, and thermogravimetric data. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2091–2100, 2004 相似文献
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Rafael Prikladnicki Alexander Boden Gabriela Avram Cleidson R. B. de Souza Volker Wulf 《Empirical Software Engineering》2014,19(4):822-856
Global Software Engineering has become a standard in today’s software industry. Research in distributed software development poses severe challenges that are due to the spatial and temporal distribution of the actors, as well as to language, intercultural and organizational aspects. These challenges occur in addition to “traditional” challenges of the domain itself in large-scale software projects, like coordination and communication issues, requirements volatily, lack of domain knowledge, among others. While several authors have reported empirical studies of global software development projects, the methodological difficulties and challenges of this type of studies have not been sufficiently discussed. In this paper, we share our experiences of collecting and analysing qualitative data in the context of Global Software Engineering projects. We discuss strategies for gaining access to field sites, building trust and documenting distributed and complex work practices in the context of several research projects we have conducted in the past 9 years. The experiences described in this paper illustrate the need to deal with fundamental problems, such as understanding local languages and different cultures, observing synchronous interaction, or dealing with barriers imposed by political conflicts between the sites. Based on our findings, we discuss some practical implications and strategies that can be used by other researchers and provide some recommendations for future research in methodological aspects of Global Software Engineering. 相似文献