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排序方式: 共有3535条查询结果,搜索用时 13 毫秒
41.
Rinaldo Gregorio Luiz Francisco Malmonge Guilherme Fontes Leal Ferreira Wilson Nunes Dos Santos Luiz Henrique Capparelli Mattoso 《应用聚合物科学杂志》2003,87(5):752-758
The real (ε′) and imaginary (ε″) components of the complex permittivity of blends of PVDF [poly(vinylidene fluoride)] with POMA [poly(o‐methoxyaniline)] doped with toluenosulfonic acid (TSA) containing 1, 2.5, and 5 wt % POMA–TSA were determined in the frequency interval between 102 and 3 × 106 Hz and in the temperature range from ?120 up to 120°C. It was observed that the values of ε′ and ε″ had a greater increase with the POMA–TSA content and with a temperature in the region of frequencies below 10 kHz. This effect decreased with frequency and it was attributed to interfacial polarization. This polarization was caused by the blend heterogeneity, formed by conductive POMA–TSA agglomerates dispersed in an insulating matrix of PVDF. The equation of Maxwell–Garnett, modified by Cohen, was used to evaluate the permittivity and conductivity behavior of POMA–TSA in the blends. A strong decrease was observed in POMA–TSA conductivity in the blend, which was bigger the lower the POMA–TSA content in the blend. This decrease could have been caused either by the POMA dedoping during the blend preparation process or by its dispersion into the insulating matrix. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 752–758, 2003 相似文献
42.
António Gaspar-Cunha Jose Ferreira Gustavo Recio 《Structural and Multidisciplinary Optimization》2014,49(5):771-793
This paper presents a new approach to robustness analysis in multi-objective optimization problems aimed at obtaining the most robust Pareto front solutions and distributing the solutions along the most robust regions of the optimal Pareto set. A new set of test problems accounting for the different types of robustness cases is presented in this study. Non-dominated solutions are classified according to their degree of robustness and are distributed along the Pareto front according to specific algorithm parameter values. Verification of the proposed method is carried out using the developed test problems and artificial and real world benchmark test problems present in the literature. 相似文献
43.
Luis Carlos Ferreira Jr.Marcos A.S. Costa Pedro Ivo C. GuimarãesLuiz Claudio de Santa Maria 《Polymer》2002,43(14):3857-3862
Styrene polymerization was carried out with Ni(acac)2/MAO and Ni(acac)2/SiO2/MAO. The influence of reaction parameters (Al/Ni mole ratio, catalyst concentration, temperature and time polymerization) on styrene polymerization was evaluated. It was observed that both catalytic systems were affected by reaction parameters and that the heterogeneous catalyst presented higher activity than the homogeneous one. Polystyrenes with different molecular weight, stereoregularity and polydispersity were obtained. These results suggest that different active catalyst species could have been present. In addition, two types of methylaluminoxane (MAO) with different molecular weights were also evaluated as cocatalyst. As a result, the catalyst activity and stereospecificity were strongly affected by the MAO type. 相似文献
44.
Chamorro G Salazar M Araújo KG dos Santos CP Ceballos G Castillo LF 《Archivos latinoamericanos de nutrición》2002,52(3):232-240
Spirulina (Arthrospira), a filamentous, unicellular alga, is a cyanobacterium grown in certain countries as food for human and animal consumption. It is also used to derive additives in pharmaceuticals and foods. This alga is a rich source of proteins, vitamins, amino acids, minerals, and other nutrients. Its main use, therefore, is as a food supplement. Over the last few years, however, it has been found to have many additional pharmacological properties. Thus, it has been experimentally proven, in vivo and in vitro that it is effective to treat certain allergies, anemia, cancer, hepatotoxicity, viral and cardiovascular diseases, hyperglycemia, hyperlipidemia, immunodeficiency, and inflammatory processes, among others. Several of these activities are attributed to Spirulina itself or to some of its components including fatty acids omega-3 or omega-6, beta-carotene, alpha-tocopherol, phycocyanin, phenol compounds, and a recently isolated complex, Ca-Spirulan (Ca-SP). This paper aims to update and critically review the results published over the last few years with regards to these properties. The conclusion is that even if this cyanobacterium has been one of the most extensively studied from the chemical, pharmacological and toxicological points of view, it is still necessary to expand the research in order to have more consistent data for its possible use in human beings. 相似文献
45.
Three formulations of mix concentrated milk with hydrosolubles extract of soybean powder and cow's milk were prepared. The products were condensed up to 31% and 33.65% of solids in a vacuum evaporator at temperature of 45 degrees and 58 degrees C with a vacuum pressure of 540 mmHg. The products obtained were compared with standard concentrated milk through sensory evaluation showing satisfactory characteristics. 相似文献
46.
Ceramic Microtubes from Preceramic Polymers 总被引:2,自引:0,他引:2
Paolo Colombo § Katia Perini Enrico Bernardo Tiziano Capelletti Giorgio Maccagnan 《Journal of the American Ceramic Society》2003,86(6):1025-1027
A novel process for the production of ceramic microtubes involving the microextrusion of preceramic polymers was studied. Microtubes with a wide range of inner and outer diameters and several centimeters long were produced from two silicone resins. A coextrusion approach was also used to extend the forming capability of the technique. The addition of carbon black resulted in electrically conductive silicon oxycarbide (SiOC) ceramic microtubes. SiOC microtubes possessed a high bending strength, ranging from ∼30–1100 MPa. 相似文献
47.
Boundary scan test,test methodology,and fault modeling 总被引:1,自引:0,他引:1
The test technique called boundary scan test (BST) offers new opportunities in testing but confronts users with new problems too. The implementation of BST in a chip has become an IEEE standard and users on board level are the next group to begin thinking about using the new possibilities. This article addresses some of the questions about changes in board-level testing and fault diagnosis. The fault model itself is also affected by using BST. Trivial items are extended with more sophisticated details in order to complete the fault model. Finally, BST appears to be a test technique that offers a high degree of detectability on board level, but for diagnosis, some additional effort has to be made. 相似文献
48.
Electrochemical tests were carried out on steel/steel multi-laminar cells under thin layers of sulphate solution simulating atmospheres with contents of 20, 50 and 75 μg m−3 of SO2 and a relative humidity of 85%. Measurements of the current flowing between the two electrodes of the cell vs drying time and impedance measurements for different times were taken. Potentiodynamic cathodic polarization plots were also obtained for one concentration of contaminant at various drying times using three electrode multi-laminar cells. The results showed that the multi-laminar cells allowed the drying process of the thin electrolyte films to be followed. The use of electrochemical techniques gave information on the kinetics and mechanism of the corrosion process occurring during the drying period. Initially the process is controlled by oxygen diffusion through the liquid film, but for longer periods the control changes to the anodic reaction. 相似文献
49.
Francisco Henrique Ferreira Ana Paula C. da Silva Alex B. Vieira 《Peer-to-Peer Networking and Applications》2016,9(1):1-15
Despite the large number of works devoted to understand P2P live streaming applications, most of them put forth so far rely on characterizing the static view of these systems. In this work, we characterize the SopCast, one of the most important P2P live streaming applications. We focus on its dynamics behavior as well as on the community formation phenomena. Our results show that SopCast presents a low overlay topology diameter and low end-to-end shortest path. In fact, diameter is smaller than 6 hops in almost 90 % of the observation time. More than 96 % of peers’ end-to-end connections present only 3 hops. These values combined may lead to low latencies and a fast streaming diffusion. Second, we show that communities in SopCast are well defined by the streaming data exchange process. Moreover, the SopCast protocol does not group peers according to their Autonomous System. In fact, the probability that a community contains 50 % of its members belonging to the same AS (when we observe the largest AS of our experiments) is lower then 10 %. Peers exchange more data with partners belonging to the same community instead of peers inside the same AS. For the largest AS we have, less than 18 % of peer traffic has been exchanged with another AS partners. Finally, our analysis provides important information to support the future design of more efficient P2P live streaming systems and new protocols that exploit communities’ relationships. 相似文献
50.