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51.
Recent measurements of nano-aluminum combustion in which burning time and peak particle temperature are measured simultaneously have suggested that heat transfer models currently used for burning nanoparticles may significantly overestimate heat losses during combustion. By applying conventional non-continuum heat transfer correlations to burning nano-aluminum particles, the observed peak temperatures, which greatly exceed the ambient temperature, should only be observable if the burning time were very short, of the order of 1 μs, whereas the observed burning time is two orders of magnitude larger. These observations can be reconciled if the energy accommodation coefficient for these conditions is of the order of 0.005, which is the value suggested by Altman, instead of approximately unity, which is the common assumption. Experimental data obtained in the heterogeneous shock tube under a wide array of conditions are compared with basic heat transfer models, and the agreement of both peak temperature values and emission intensity traces for low energy accommodation coefficients supports the hypothesis of Altman and co-workers. 相似文献
52.
Daniella Regina Mulinari Herman J.C. Voorwald Maria Odila H. Cioffi Maria Lúcia C.P. da Silva Tessie Gouvêa da Cruz Clodoaldo Saron 《Composites Science and Technology》2009
Natural fibers used in this study were both pre-treated and modified residues from sugarcane bagasse. Polymer of high density polyethylene (HDPE) was employed as matrix in to composites, which were produced by mixing high density polyethylene with cellulose (10%) and Cell/ZrO2·nH2O (10%), using an extruder and hydraulic press. Tensile tests showed that the Cell/ZrO2·nH2O (10%)/HDPE composites present better tensile strength than cellulose (10%)/HDPE composites. Cellulose agglomerations were responsible for poor adhesion between fiber and matrix in cellulose (10%)/HDPE composites. HDPE/natural fibers composites showed also lower tensile strength in comparison to the polymer. The increase in Young’s modulus is associated to fibers reinforcement. SEM analysis showed that the cellulose fibers insertion in the matrix caused an increase of defects, which were reduced when modified cellulose fibers were used. 相似文献
53.
54.
Martijn Kuik Gert‐Jan A. H. Wetzelaer Jurre G. Laddé Herman T. Nicolai Jurjen Wildeman Jörgen Sweelssen Paul W. M. Blom 《Advanced functional materials》2011,21(23):4502-4509
The effect of on‐chain ketone defects on the charge transport of the polyfluorene derivative poly(9,9‐dioctylfluorene) (PFO) is investigated. Using MoO3 as ohmic hole contact, the hole transport in a pristine PFO diode is observed to be limited by space‐charge, whereas fluorenone contaminated PFO (PFO‐F) is shown to be trap limited by the occurrence of an exponential trap distribution with a trap depth of 0.18 eV. The electron transport in PFO is also observed to be trap limited, but in order to describe the electron transport of PFO‐F, an additional trap level with a depth of 0.46 eV must be introduced. The obtained energy levels of the fluorenone trapping sites are in close agreement with cyclic voltammetry (CV) measurements reported in literature. As a result, the fluorenone defects are shown to simultaneously act as hole‐ and electron trap. Moreover, through ideality factor measurements, the green emission associated with these defects is observed to originate from trap‐assisted recombination. 相似文献
55.
56.
Aurelie Wauthier Helene Regle Jorge Formigoni Gwenola Herman 《Materials Characterization》2009,60(2):90-95
Asymmetrical rolling is a promising way to achieve high rolling reductions and potentially grain refinement. However in steels the effect of asymmetrical rolling is not thoroughly quantified. In this paper the impact of cold asymmetrical rolling obtained by changing the roll velocity ratio (from 1.1 to 1.45) on the deformation and recrystallization features has been finely investigated by Electron Back-Scattering Diffraction in a Scanning Electron Microscope. In the investigated conditions (with low thickness reduction), it is found that asymmetrical rolling induces grain refinement and more homogeneous gamma fiber texture. 相似文献
57.
Jantien A. Backer Thomas J. Hagenaars Herman J.W. van Roermund Mart C.M. de Jong 《Journal of the Royal Society Interface》2009,6(39):849-861
In a recent update of the Dutch contingency plan for controlling outbreaks of classical swine fever (CSF), emergency vaccination is preferred to large-scale pre-emptive culling. This policy change raised two questions: can emergency vaccination be as effective as pre-emptive culling, and what are the implications for showing freedom of infection? Here, we integrate quantitative information available on CSF virus transmission and vaccination effects into a stochastic mathematical model that describes the transmission dynamics at the level of animals, farms and livestock areas. This multilevel approach connects individual-level interventions to large-scale effects. Using this model, we compare the performance of five different control strategies applied to hypothetical CSF epidemics in The Netherlands and, for each of these strategies, we study the properties of three different screening scenarios to show freedom of infection. We find that vaccination in a ring of 2 km radius around a detected infection source is as effective as ring culling in a 1 km radius. Feasible screening scenarios, adapted to the use of emergency vaccination, can reduce the enhanced risks of (initially) undetected farm outbreaks by targeting vaccinated farms. Altogether, our results suggest that emergency vaccination against CSF can be equally effective and safe as pre-emptive culling. 相似文献
58.
In the present research it is reported the synthesis and characterization of CdS nanoparticles (NPs) prepared using carboxylic-functionalized poly (vinyl alcohol) (PVA) as the ligand via aqueous route at room temperature and ambient pressure. Different molar concentrations of carboxylic-PVA and PVA were investigated aiming at producing stable colloidal systems. Carboxylic-PVA was conjugated with BSA (bovine serum albumin) and used as capping ligand in the preparation of CdS nanocrystals. UV-visible spectroscopy, photoluminescence spectroscopy, and transmission electron microscopy were used to characterize the kinetics and the relative stability of polymer-capped CdS nanocrystals. The results have clearly indicated that the carboxylic-functionalized PVA was much more effective on nucleating and stabilizing colloidal CdS nanoparticles in aqueous suspensions compared to PVA. In addition, the CdS nanocrystals were obtained in the so-called “quantum-size confinement regime”, with the calculated average size below 4.0 nm and fluorescent activity. Thus, a novel simple route was successfully developed for synthesizing nanohybrids based on quantum dots and water-soluble chemically functionalized polymers with incorporated carboxylic moiety with the possibility of direct bioconjugation. 相似文献
59.
Proportional symbol maps visualize numerical data associated with point locations by placing a scaled symbol—typically an
opaque disk or square—at the corresponding point on a map. The area of each symbol is proportional to the numerical value
associated with its location. Every visually meaningful proportional symbol map will contain at least some overlapping symbols.
These need to be drawn in such a way that the user can still judge their relative sizes accurately. 相似文献
60.
Solid waste treatment options (recycling, incineration, and landfilling; the two latter processes both with co-generation of heat and electricity) have been studied for cardboard, newspaper, polyethylene, poly(ethylene terephthalate), polypropylene, polystyrene, and poly(vinyl chloride) waste. The conversion processes have been analyzed in terms of the second law of thermodynamics. The analysis allows calculating the exergy (useful energy) embodied in conversion products that can be obtained from the required inputs for the treatment processes. Taking into account the waste materials and the resources to convert them, it proved that recycling is the most efficient option for polyethylene with an efficiency of 62.5% versus 43.6% for incineration and 0.9% for landfilling. Next, waste treatment has been put into the broader perspective of industrial ecology. Exergetic efficiencies of industrial metabolic options have been calculated. Here resources for manufacturing and converting solid products have been considered. Furthermore, selection of one type of conversion excludes the generation of other potential conversion products. Therefore, it has to be taken into account that these latter products still have to be produced starting from virgin resources. Recycling proved to be the most efficient strategy: the ratio eta between exergy embodied in all delivered products on one hand, and all exergy withdrawn from the ecosphere or from waste materials on the other hand, is the highest. For polyethylene, eta proved to be 0.568, whereas eta is 0.503 and 0.329 for incineration and landfilling, respectively. On the other hand, if R the ratio between exergy of delivered products on one hand and exergy of virgin materials on the other hand is calculated, the differences between the industrial metabolic options are larger. Recycling polyethylene showed a ratio R of 0.936, whereas ratios of 0.772 and 0.531 were found for incineration and landfilling, respectively. It has been shown that the exergy concept allows a quantitative comparison of different industrial metabolic options, contributing to a better assessment of sustainability of technology with respect to resource management. 相似文献