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排序方式: 共有174条查询结果,搜索用时 31 毫秒
31.
Summary Blends containing poly(N-vinyl-2-pyrrolidone) (PVP) and poly(hydroxyethyl methacrylate) (PHEMA) with (styrene-co-dimethyl itaconate) (Sty-co-DMI) and (styrene-co-diethylitaconate) (Sty-co-DEI) copolymers of three different compositions were studied. One Tg value over the whole range of compositions is observed for the majority of the blends, what is indicative of compatibility. The Gordon-Taylor kGT and the Couchman kC parameters were determined for all the blends in order to compare the strength of the interactions. The effect of the side chain structure of the copolymer on the miscibility of these blends is analyzed. 相似文献
32.
Abstract: Thermal stresses resulting from flow of hot and cold water were obtained in sinks manufactured with acrylic casting dispersions by both experimental and numerical analysis. The experimental work was performed in two poly(methyl methacrylate) (PMMA) -silica based particulate composites, compositions of which are different by the volume fraction of filler and the particle size. The thermal stresses in sinks were obtained using strain gauges. The alternate flow of cold and hot water using a mixed tap, results in the formation of thermal gradients, leading to the occurrence of thermal stresses . The experimental results were compared with the numerical results obtained with a commercial finite element software. For this analysis, some thermal parameters such as the convective heat transfer coefficient, the density, the thermal conductivity and the specific heat were experimentally obtained. In general, a good agreement between experimental and numerical results was observed. The results of this study, together with the results of fatigue and fracture tests, will be used in a tolerance analysis of defects in the products manufactured with these composites. 相似文献
33.
Mirela Araújo de Oliveira Geraldo Arraes Maia Raimundo Wilane de Figueiredo Arthur Cláudio Rodrigues de Souza Edy Sousa de Brito & Henriette Monteiro Cordeiro de Azeredo 《International Journal of Food Science & Technology》2009,44(3):641-645
This study involved an attempt to totally or partially replace maltodextrin DE10 (MD10) by cashew tree gum (CTG) as a drying aid agent in spray drying of cashew apple juice. The objective was to evaluate the impact of drying aid/cashew apple juice dry weight ratio (D/C, ranging from 3 to 5) and degree of replacement of MD10 with CTG (CTGR , ranging from 0% to 100%) on ascorbic acid retention (AAR), hygroscopicity, flowability and water solubility of spray dried cashew apple juice powder. AAR was increased from 72.90% to 95.46% by increasing D/C from 3 to 5. CTG was shown as a promising maltodextrin replacer, being more effective than the latter to decrease powder hygroscopicity. The most adequate drying conditions (D/C = 5, CTGR ≥50%) resulted in more than 90% of AAR, and produced a powder with good flowing properties and water solubility. 相似文献
34.
Poly(thiocarbonates) with alkyl side chains have been prepared, and the solution properties of these polymers were studied in different solvents. Comparison with other poly(thiocarbonate) analogues and poly(carbonates) shows that the conformational parameter (Kθ) and rigidity factor increase as the volume of the side chain increases. The effect of the side-chain structure on the solution properties is analyzed. 相似文献
35.
Summary The preferential adsorption parameter of poly(phenyl methacrylate), poly[4-(1,1,3,3- tetramethylbutyl) phenyl methacrylate] and poly(4-tert-butyl styrene) in the mixture THF/water has been determined by exclusion chromatography (GPC) and differential refractometry and dialysis equilibrium (DR). The general behaviour of the polymers studied in this mixture is very similar, water is preferentially adsorbed by the polymer at low water content. The results are discussed in relation to the rigidity of the macromolecular chains and the hydrophobic degree of the substituent group in the aromatic ring. 相似文献
36.
37.
The miscibility of blends of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) and poly(vinylpyrrolidone) (PVP) was studied by differential scanning calorimetry (DSC) through the analysis of the glass transition temperature Tg. The dependence of Tg with the annealing temperature was determined for PPO and PVP samples of different molecular weights. The phase diagrams for blends containing three different PVP samples were established. Blends of PPO and PVP were found to be miscible for composition lower than 30% and higher than 65% of PVP. A inmiscibility window between 30 and 65% of PVP is also described. 相似文献
38.
Francisco A. Macías Ana M. Simonet Brigida D’Abrosca Claudia C. Maya Matías Reina Azucena González-Coloma Raimundo Cabrera Cristina Giménez Luis Villarroel 《Journal of chemical ecology》2009,35(1):39-49
The new bioactive sesquiterpenoid (3R,6E)-2,6,10-trimethyl-3-(3-p-hydroxyphenylpropanoyloxy)-dodeca-6,11-diene-2,10-diol, named megalanthine, was isolated from the resinous exudates of Heliotropium megalanthum. The degradation products of this compound were identified. Several plant-defensive properties (insecticidal, antifungal,
and phytotoxic) were evaluated after obtaining positive results in a preliminary etiolated wheat coleoptile bioassay. This
bioassay showed the need to have both the phenolic and sesquiterpene moieties of the natural product present to achieve a
biological effect. This result was confirmed in phytotoxicity bioassays. Megalanthine was ruled out as a significant plant–plant
defense agent because of its lack of stability. The positive results recorded in the antifungal and antifeedant tests suggest,
however, that this chemical is relevant in several ecological interactions involving H. megalanthum. 相似文献
39.
Raimundo Barreto Paulo Maciel Eduardo Tavares Romulo Devezas Freitas Meuse Oliveira Ricardo Massa Lima 《Design Automation for Embedded Systems》2008,12(1-2):31-62
Over the last few years, embedded software synthesis has drawn much attention. However, few works deal with software synthesis for hard real-time systems considering arbitrary inter-tasks precedence and exclusion relations. Code generation for meeting all timing and resource constraints is not a trivial task. Thus, this research area has several open issues, mainly related to generation of predictable-guaranteed scheduled code. The method proposed in this paper starts from a high-level specification, and automatically translates such specification into a time Petri net model; this model is adopted for finding a feasible static schedule meeting all constraints. If found, the approach generates a scheduled code, based on the found feasible schedule. Therefore, the user just enter the specification and receives, as result, the scheduled code. Thus, all intermediary phases are hidden from the users. 相似文献
40.
da Silva Paulo F. Santana Ewaldo E. C. Cruz Carlos A. M. Aquino Vivianne S. Castro Luís S. O. Serres Alexandre J. R. Freire Raimundo C. S. Silva Paulo H. F. 《Wireless Personal Communications》2021,119(1):329-341
Wireless Personal Communications - This paper presents the development of a compact monopole antenna bioinspired in the Opuntia ficus-indica plant-shape, generated by Gielis formula, built in... 相似文献