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排序方式: 共有1183条查询结果,搜索用时 15 毫秒
1.
Ahmed Bazil Taha Carreras Darío Castro Marin Eduardo Garcia 《Wireless Personal Communications》2021,117(4):2757-2780
Wireless Personal Communications - Semantic Web content extracting are the augmentation of the present web where the data is given in the better importance and allowing users to work close by close... 相似文献
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Marcela Stoia Cornelia Păcurariu Ciprian Mihali Iosif Mălăescu Cătălin Nicolae Marin Aylin Căpraru 《Ceramics International》2019,45(2):2725-2735
Magnetic MnFe2O4 nanopowders were synthesized by an original solvothermal method in the absence and in the presence of tetra-n-butylammonium bromide (TBAB) and Tween 80 (TW) as surfactants. Manganese ferrite/polyaniline (PANI) hybrid materials were synthesized by in situ polymerization of aniline on the surface of MnFe2O4 using ammonium persulfate as oxidant. The purpose of the study was to investigate the influence of the two surfactants on the properties of the MnFe2O4 powders and of their composites with PANI. The specific surface area, the cumulative surface area of pores and the cumulative volume of pores are influenced by the nature of surfactant in case of MnFe2O4 powders and are higher by comparison to those of the MnFe2O4/PANI hybrid materials. The values of saturation magnetization in case of MnFe2O4 powders are higher than those of the hybrid materials and are not influenced by the surfactant nature. These features revealed that MnFe2O4 powders can be efficiently used as adsorbents for the purification of wastewaters. The values of the electrical conductivity of the composites exhibit a significant increase in comparison to the MnFe2O4 powders and depend on the surfactant nature. The highest value of electrical conductivity was achieved by the composite obtained using Tween 80 as surfactant (σDC = 54.5·10?5S?m?1) which was close to that of PANI (σDC = 61.2·10?5 S?m?1). The fact that the magnetic and electric properties of the synthesized MnFe2O4/PANI composites can be changed by design, demonstrate the high potential of these materials to be used in magneto-electric applications. 相似文献
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Earth to air heat exchanger (EAHE) is a well‐known technique used to preheat or precool outdoor air before blowing it into a building. However, its geometry is often very simple as it consists in one or multiple straight pipes, while more complex arrangements can be found in heat exchangers design. In this paper, we explore the advantage of designing an EAHE as a network through the Constructal law point of view. A methodology is first proposed to design a single pipe EAHE when the need is defined in terms of cooling power, overall efficiency and enthalpy difference between the inlet air and the ground. Next, the single pipe EAHE is used as a reference for designing a tree‐shaped network under the constraint of identical fluid volume and cooling power. The geometrical features are allowed to change for the different branches of the network. The network coefficient of performance is found to increase significantly with the bifurcation level, illustrating the superior performances of the network. This approach was found to be robust as the improvements were not depending on the cooling demand or the environmental conditions. However, further work is needed to move from this theoretical result to practical considerations. 相似文献
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Rachel E. Pepper Emily E. Riley Matthieu Baron Thomas Hurot Lasse Tor Nielsen M. A. R. Koehl Thomas Kirboe Anders Andersen 《Journal of the Royal Society Interface》2021,18(175)
Microscopic sessile suspension feeders live attached to surfaces and, by consuming bacteria-sized prey and by being consumed, they form an important part of aquatic ecosystems. Their environmental impact is mediated by their feeding rate, which depends on a self-generated feeding current. The feeding rate has been hypothesized to be limited by recirculating eddies that cause the organisms to feed from water that is depleted of food particles. However, those results considered organisms in still water, while ambient flow is often present in their natural habitats. We show, using a point-force model, that even very slow ambient flow, with speed several orders of magnitude less than that of the self-generated feeding current, is sufficient to disrupt the eddies around perpendicular suspension feeders, providing a constant supply of food-rich water. However, the feeding rate decreases in external flow at a range of non-perpendicular orientations due to the formation of recirculation structures not seen in still water. We quantify the feeding flow and observe such recirculation experimentally for the suspension feeder Vorticella convallaria in external flows typical of streams and rivers. 相似文献
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Marisa De Sousa Duarte Matthieu Rolland Corinne Sagnard Didier Suire Frederic Flacher Olivier Delpoux Charles P. Lienemann 《化学工程与技术》2019,42(3):655-660
A 3‐MPa, 350 °C fixed‐bed reactor was designed to follow‐up gas‐liquid‐solid reactions on a millimetric size heterogeneous catalyst with Raman spectroscopy. The transparent reactor is a quartz cylinder enclosed in a Joule effect heated stainless‐steel tube. A methodology to determine how to focus the microscope for liquid and solid phase characterization is presented. The setup was validated by performing diesel hydrodesulfurization on a CoMo/alumina extrudate catalyst with a conversion very close to expected values along with the acquisition of Raman spectra of the solid catalyst showing an evolution of the catalyst phase during sulfidation. 相似文献
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The Italian economy is characterised by a large number of micro-firms and small firms and by a long-lasting gap between North and South Italy. Therefore, global shocks – such as the Great Recession – have had a heterogeneous impact at the local level: the collapse in private demand was unequally distributed across different products, services and regions. The aim of this paper, therefore, is to evaluate the impact of the Great Recession on firm's survival for the universe of Italian firms in the light of two relevant indicators: local exposure to crisis and local demand shocks. The results suggest a strong negative impact of local demand shocks on the survival of firms, whereas the degree of exposure to the crisis generally has a weak effect. 相似文献