摘要：
Solidification/stabilization is considered to be a well-established disposal technique for reducing sludge handling and disposal obstacles. In this work, a slag-based solidification material (SBSM) was developed, using slag and dihydrate gypsum as the solidifier and sulphoaluminate cement clinker as the additive, to improve the performance of sludge solidification and thus making sludge disposal and recycling possible. The behaviour of pastes fabricated with various mass ratios of slag/sulphoaluminate cement clinker/dihydrate gypsum has been analysed in terms of mechanical strength, hydration products, microstructure, and toxicity characteristics. The results show that the strength of solidified sludge increased significantly with the addition of SBSM and the sulphoaluminate cement clinker content in SBSM. The use of sulphoaluminate cement clinker significantly improved the solidification/stabilization performance, causing a higher strength level. X-ray diffraction and scanning electron microscopy investigations revealed that a large amount of ettringite was present in the solidified sludge, leading to a crystallizing network in the solidified products and therefore the enhancement of the strength. Environmental assessment of the final products in compliance leaching tests demonstrated that the concentration of heavy metals were below the detection limits (GB5085.3-2007) set in China.
关键词：
nanofluids;laminar flow;forced convection;heat transfer enhancement
摘要：
A theoretical answer to the controversial issue on the anomalous convective heat transfer in nanofluids has been provided, exploiting the Buongiorno model for convective heat transfer in nanofluids with modifications to fully account for the effects of nanoparticle volume fraction distributions on the continuity, momentum, and energy equations. A set of exact solutions have been obtained for hydrodynamically and thermally fully developed laminar nanofluid flows in channels and tubes, subject to constant heat flux. From the solutions, it has been concluded that the anomalous heat transfer rate, exceeding the rate expected from the increase in thermal conductivity, is possible in such cases as titania-water nanofluids in a channel, alumina-water nanofluids in a tube and also titania-water nanofluids in a tube. Moreover, the maximum Nusselt number based on the bulk mean nanofluid thermal conductivity is captured when the ratio of Brownian and thermophoretic diffusivities is around 0.5, which can be exploited for designing nanoparticles for high-energy carriers.
摘要：
This laboratory study explores the development of plastering mortar modified by feather fibers, so as to lay the groundwork for utilizing poultry feathers in thermal- insulation materials and removing them from waste streams. The laboratory testing measured the consistency value, porosity, compressive strength and thermal conductivity of various cement mortar mixes as a function of feather fiber dosage. The experimental data were used to determine the appropriate weight fraction of feather fibers in the mortars for thermal insulation. The results indicate that the incorporation of feather fibers decreased the consistency value of fresh mortar and increased the surface roughness and porosity of hardened mortar. Under the investigated conditions, as the content of admixed fiber increased, both the compressive strength and thermal conductivity of hardened mortar decreased remarkably before leveling off. The desirable dosage of feather fibers falls in the range of 0.2-0.7% by mass of dry mixture.
关键词：
anti-icing;winter road maintenance;snow and ice control;fixed automated spray technology;evaluation;antigivrage;entretien des routes en hiver;contrôle de la neige et de la glace;technologie d’arrosage automatisé fixe;évaluation
摘要：
This paper synthesizes information obtained from a comprehensive literature review and agency surveys on the state of the practice of fixed automated spray technology (FAST) systems. Experience with FAST systems in North America and Europe has revealed a mixed picture. On the one hand, several studies have indicated reductions in mobile operation costs and significant reductions in crash frequency, resulting in favorable benefit-cost ratios. On the other hand, there have been a variety of problems related to activation frequency, system maintenance and training. Installing a FAST system is complex and the challenges are often site specific. However, the evaluations cited show that FAST systems can be cost-beneficial if their locations are carefully chosen and if the system is supported with reliable environmental sensors. Finally, it was found that application of FAST systems in North America have recently increased.
关键词：
Hollow Fiber;Blood Flow Rate;Oxygen Transfer Rate;Shell Side;Dimensionless Length
摘要：
A porous media theory has been proposed to characterize oxygen transport processes associated with membrane blood oxygenation devices. For the first time, a rigorous mathematical procedure based a volume averaging procedure has been presented to derive a complete set of the governing equations for the blood flow field and oxygen concentration field. As a first step towards a complete three-dimensional numerical analysis, one-dimensional steady case is considered to model typical membrane blood oxygenator scenarios, and to validate the derived equations. The relative magnitudes of oxygen transport terms are made clear, introducing a dimensionless parameter which measures the distance the oxygen gas travels to dissolve in the blood as compared with the blood dispersion length. This dimensionless number is found so large that the oxygen diffusion term can be neglected in most cases. A simple linear relationship between the blood flow rate and total oxygen transfer rate is found for oxygenators with sufficiently large membrane surface areas. Comparison of the one-dimensional analytic results and available experimental data reveals the soundness of the present analysis.
摘要：
This investigation aimed to study the interaction between concrete substrate and silicone rubber sealant. Several surface treatments were applied in order to obtain different levels of surface roughness in concrete substrates. The bond tensile test showed that abrasion and solvent cleaning methods improved the bond strength relative to that of untreated substrates. The effects of silane coupling agents on the bond strength was studied via two methods of application of the coupling agent, namely, (a) pre-treatment of concrete substrate in an aqueous solution of silane, and (b) adding silane to the silicone rubber sealant as an integral blend additive. No significant differences in bonding values were noted between the two methods. An increase in the amount of silane coupling agent increased the bond strength of the silicone rubber sealant, but beyond a certain point, further increases in the amount of silane lowered the bond strength. As the amount of silanes increased, the failure mode of the samples changed from adhesive failure to cohesive failure. Scanning electron microscopy and contact angle methods were employed to investigate the interface. The results strongly suggest that interface adhesion and treatments are crucial factors in creating a durable bond interface between substrate and sealant.
摘要：
Nano-silica particles were deposited on acid-etched hydrophilic aluminum (Al) substrates by immersion in well-dispersed nano-silica aqueous suspension and tetramethylamonium hydroxide, followed by a heat treatment. The surface was then further treated by a reaction with fluorosilane. The hydrophobicity, surface morphology, and mechanical properties of the coated Al substrates were investigated, along with their electrochemical properties over time of exposure to two NaCl solutions (0.3% and 3% by weight). All the coated Al surfaces exhibited a water contact angle of 155–158°, i.e., superhydrophobicity. The use of nano-silica suspension significantly enhanced the hydrophobicity of the coated Al. Artificial neural networks were used to provide quantitative understanding in how the microstructure of the treated Al surface contributed to its superhydrophobicity and electrochemical properties. When Ra, total (nano-roughness + micro-roughness) exceeds 450 nm, WCA is greater than 154°, independent of the nano/micro-roughness ratio (RRNM). FESEM and AFM images of these surfaces suggest that a rough two-length-scale hierarchical structure coupled with the low surface energy of fluorosilane topcoat led to the superhydrophobicity of the formed coatings. The coating prepared with the 0.2% nano-silica suspension (vs. other concentrations) featured the highest Young's modulus and the best corrosion protection to the Al substrate in both NaCl solutions.
摘要：
A porous media approach based on the volume-averaging theory has been proposed to investigate solute diffusion and ultrafiltration processes associated with hemodialysis using a hollow fiber membrane dialyzer. A general set of macroscopic governing equations has been derived for the three individual phases, namely, the blood phase, the dialysate phase, and the membrane phase. Thus, conservations of mass, momentum, and species are considered for blood compartments, dialysate compartments, and membranes within a dialyzer to establish a three concentration equation model. These macroscopic equations can be simultaneously solved for the various cases of inlet velocities of blood and dialysate. An analytic expression for the solute clearance was obtained for the one-dimensional case, in which important dimensionless parameters controlling the dialyzer system are identified for the first time.
摘要：
An effective porosity concept has been introduced to account for the effects of tortuosity and thermal dispersion on the individual effective thermal conductivities of the solid and fluid phases in a fluid-saturated porous medium. Using this effective porosity concept, a thermal nonequilibrium model has been proposed to attack locally thermal nonequilibrium problems associated with convection within a fluid-saturated porous medium. Exact solutions are obtained, assuming a plug flow, for the two cases of thermally fully developed convective flows through a channel, namely, the case of isothermal hot and cold walls and the case of constant heat flux walls. These exact solutions for the cases of metal foam and air combination reveal that the local thermal equilibrium assumption may hold for the case of isothermal hot and cold walls, but may fail for the case of constant heat flux walls.
