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This paper reports research on the effects of variations in injection velocity and permeability on the heat transfer and flow
through a highly porous medium between two horizontal parallel plates situated at constant distance with constant suction
by the upper plate. Due to this type of variation in injection velocity and in permeability the flow becomes three dimensional.
The governing equations are solved by adopting complex variable notations to obtain the expressions for the velocity and temperature
field. The skin-friction along the main flow direction and rate of heat transfer are discussed with the help of graphs. 相似文献
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讨论了当0<m<1-2/N(N≥3)时,柯西问题ut=Δum-up u(x,0)=0 x∈RN\{0}的非平凡解的存在性. 相似文献
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《Journal of Cultural Heritage》2014,15(2):151-158
Nanolime dispersed in 2-propanol was extensively used for the consolidation of wall paintings. The knowledge of the advances of this methodology dealing with all the possible effects associated with the nanolime new material in conservation is fundamental to assess and improve the technique. In this paper, four different dispersions of Ca(OH)2 nanoparticles were characterised by Small Angle X-rays Scattering technique (SAXS) and Transmission Electron Microscopy (TEM) in order to achieve information on size, shape, polydispersity, agglomeration, and crystal structure (by SAED patterns) of the particles. Once characterised, the dispersions were tested in two different case studies, the Carceri dello Steri in Palermo with their graffiti and the 18th century lunettes at the SS. Giuda e Simone Cloister, Corniola (Empoli) with their lime-based mural paintings. The treated samples were characterised in relationship to either their morphology and surface chemical composition by Scanning Electron Microscopy coupled with Energy Dispersive X-rays spectroscopy (SEM-EDX), or their water absorption and mechanical properties (resistance to material abrasion). The results obtained showed that all the dispersions were nanometrically structured and their application succeeded in recovering the mechanical properties of the painting or graffito layers, not altering their permeability to water and keeping perfectly the wall transpiration. However, the dispersions constituted of the nanoparticles obtained via a synthesis able to control size and shape of the Ca(OH)2 particles resulted in a better performance in situ, even if the differences found by SAXS and TEM were slight. 相似文献
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Soil in a cold region is subject to frequent freezing and thawing cycles. Soil frozen for a prolonged period may cause adverse freeze damage to the plants due to cell dehydration or root cell rupture. It is important to understand the detailed heat transfer behaviors of the freezing and thawing processes to prevent freeze damage, and to devise proper mitigation measures for effective pot planting in cold regions. A theoretical model was developed to analyze the transient moving phase-change interface heat transfer in the freezing and thawing of porous potting soil. The theoretical derivation is based on the assumption that the soil freezes completely at a single temperature. Microscopic poromechanic effects on heat transfer behavior were ignored. The spatial domain of the problem was simplified to a 1 D spherical coordinate system with variation in the radial direction. Green's function was applied to solve for the time-dependent body temperature. Experiments were conducted for validation of the theoretical model Reasonable agreement between the theoretical predictions and experimental measurements was obtained. The theoretical model developed can be easily used to determine the sensitivity of various parameters in the freezing/thawing processes, e.g., thermal properties of soil, ambient temperature, and planting pot size. 相似文献
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INDRODUCTIONMeso-poroussilicafilmswithanexcellentheat-insulatingpropertyandtherelativelylowdielectricvalueplayparticularlyimportantroleinelectronicandmagneticdevices(Moonetal.,1997),etc.;thosewithporesizesof5nmto50nmarealsoofinterestforapplicationsinphotonics,optoelec-tronics,lightweightstructuralmaterialthermalin-sulation,opticalcoating(Moonetal.,1997;HusingandSchulert,1998;Davis,2002).Theirspecialnetworkstructureisusedinsounddetector(HusingandSchubert,1998);theirexcellentinsulatingpro… 相似文献
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Zhao Y Li DS Xing SX Yang DR Jiang MH 《Journal of Zhejiang University. Science. B》2005,6(11):1135-1140
INTRODUCTION Porous silicon (PS) attracts the attention of many researchers due to the possibility of developing PS based devices, including optoelectronics, photo re- sistors, solar cells and light emitting diodes (Balucani et al., 1999; Palma et al., 1999a; Stievenard and Deresmes, 1995). To integrate PS into electronic circuits or to develop PS based devices, the electrical properties of this material must be studied thoroughly. It is a difficult case because this material has a ve… 相似文献
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针对目前差压流量计的不足,提出了一种新型的节流式差压流量计---多孔双钝头体流量计。根据数值模拟结果,该装置在规则来流情况下,能够对流动起到很好的整流效果,提高测量的精确度和重复性;同时,在双钝头体上开孔,可以减小压力损失。通过数值模拟结果与实验结果的比对,验证了数值模拟的可靠性。 相似文献