用概率统计方法增强结构木质复合材料的竞争力

Hunt在1976年曾撰文呼吁,重视结构用刨花板(主要为大片刨花板)的广泛应用及结构可靠性设计方法的引入,为木质复合材料工业发展带来了大好局面。他认为具有更高稳定性的建筑材料,特别是如工程复合材料之类,可以通过改善设计、工艺过程和质量控制等方式来提高其质量稳定性;通过以可靠性为基础的设计方式     

Degradation rate quantification of solid oxide fuel cell performance with and without Al2TiO5 addition

Degradation rates of electrical current during constant voltage operation of SOFCs with anodes made using NiO precursor powders from two different manufacturers with and without the addition of aluminum titanate (ALT) added by either mechanical mixing or anode infiltration have been quantified using a novel MATLAB algorithm. Because the algorithm has been used to quantify degradation rates for many different SOFC tests, it is thought that the method can be applied to most measured SOFC data to quantify the instantaneous cell degradation rate as a function of time for the entire SOFC performance measurement. Degradation rates determined at different times have been plotted against varying concentrations of ALT addition, facilitating the estimation of optimum ALT concentration for SOFC anodes made with NiO from a specific manufacturer. The algorithm used to determine degradation rates is available upon request to the corresponding author.     

A multi-year composite of GVI data as a clear reflectance database

A method is developed to generate a top of the atmosphere clear reflectance from the Global Vegetation Index (GVI) product. Our goal is to use this dataset as a threshold to be applied to the forthcoming POLDER observations, for operational cloud detection. The method is based on the hypothesis that clouds add a high frequency signal to the slow variations of the surface reflectance in clear conditions. The validity of our algorithm is verified through an analysis of the temporal profile of the reflectance that it generates. We show that these profiles are better than those resulting from the simpler Maximum Value Composite (MVC) method. The method is applied to five years of GVI products and the results are used to derive a reference database which accounts for the interannual variability of the surface reflectance.     

Localization of trehalose in partially hydrated DOPC bilayers: insights into cryoprotective mechanisms

Trehalose, a natural disaccharide with bioprotective properties, is widely recognized for its ability to preserve biological membranes during freezing and dehydration events. Despite debate over the molecular mechanisms by which this is achieved, and that different mechanisms imply quite different distributions of trehalose molecules with respect to the bilayer, there are no direct experimental data describing the location of trehalose within lipid bilayer membrane systems during dehydration. Here, we use neutron membrane diffraction to conclusively show that the trehalose distribution in a dioleoylphosphatidylcholine (DOPC) system follows a Gaussian profile centred in the water layer between bilayers. The absence of any preference for localizing near the lipid headgroups of the bilayers indicates that the bioprotective effects of trehalose at physiologically relevant concentrations are the result of non-specific mechanisms that do not rely on direct interactions with the lipid headgroups.     

An investigation of colour appearance for unrelated colours under photopic and mesopic vision

Data were obtained for the colour appearance of unrelated colours under photopic and mesopic conditions. The effects of changes in luminance level and stimulus size were investigated. The method used was magnitude scaling of brightness, colourfulness, and hue. Two stimulus sizes (10° and 0.5°) and four starting luminance levels (60, 5, 1, and 0.1, cd/m²) were used. The results at 0.1 cd/m² had large variations, so data were obtained for two additional stimulus sizes (1° and 2°) at this luminance level. Ten observers judged 50 unrelated colours. A total of 17,820 estimations were made. The observations were carried out in a completely darkened room, after 20 min adaptation; each test colour was presented on its own. Brightness and colourfulness were found to decrease with decreases of both luminance level and stimulus size. The CAM97u model predicted brightness more accurately than CIECAM02 but gave worse performance in predicting colorfulness. For hue, CAM97u and CIECAM02 both gave satisfactory predictions. Using the brightness correlate from CAM97u, a new colour‐appearance model based on CIECAM02 was developed specifically for unrelated colours under photopic and mesopic conditions, with parameters to allow for the effects of luminance level and stimulus size. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011;     

The Single-Fiber Collision Rate and Filtration Efficiency for Nanoparticles I: The First-Passage Time Calculation Approach

We describe an approach to filtration-efficiency calculations as an alternative to the traditional depth filtration theory. The new approach involves linking the single-fiber efficiency to the collision rate coefficient/kernel between nanoparticles and fibers, and correspondingly inferring the collision kernel via dimensionless mean first-passage time (MFPT) calculations. This method has the advantage of easily incorporating the influences of particle diffusion, inertia, and particle size; therefore, all filtration mechanisms can be considered simultaneously. Through non-dimensionalization of the equation of motion for a particle in MFPT calculations (the Langevin equation), it is shown that both the single-fiber efficiency E_f and dimensionless particle-fiber collision kernel, H, are functions of the ratio of particle radius to filter-fiber radius, R, the solid volume fraction in the filter, V_f, the ratio of particle persistence distance to the particle-filter collision distance, Kn_D (the diffusive Knudsen number), and the ratio of the particle translational kinetic energy to the thermal energy χ_f. Using a Kuwabara flow-cell model to define the geometry and flow field, MFPT calculations are used to determine H and E_f for nanoparticles in atmospheric pressure systems, i.e., when particle inertia is negligible but when diffusion and interception act in tandem to collect particles. From MFPT results, regression equations for both H and E_f are developed. A comparison is made between MFPT results and commonly invoked depth-filtration single-fiber efficiency relationships, experimentally measured values, and H equations derived from Sherwood number correlations based upon measurements of heat transfer from a fluid flowing perpendicular to an array of cylinders. Good agreement is found with both measurements and previously developed equations over a wide range of parameter space.

Copyright 2014 American Association for Aerosol Research     

Investigation of fluidized bed behaviour using electrical capacitance tomography

The temporal and cross-sectional distributions of particles in a 127 mm diameter fluidized bed have been obtained using a new generation, high-speed electrical capacitance tomography. Two planes of eight electrodes were used and mounted at 160 and 660 mm from the gas distributor which was a 3 mm thick porous plastic plate (maximum pore size of 50-70 μ m). 3 mm diameter, nearly-spherical polyethylene granules made up the bed. Experiments at sampling frequencies of 200-2000 cross-sections per second and gas superficial velocities from just below the minimum fluidization to 83% above minimum fluidization velocities were used. The time series of the cross-sectional average void fractions have been examined both directly and in amplitude and frequency space. The last two used probability density functions and power spectral densities. The information gathered shows that the fluidized bed was operating in the slugging mode, which is not surprising given the size of the particles. It has been found that an increase in the excess gas velocity above the minimum fluidization velocity resulted in an increase in the mean void fraction, an increase in the length and velocity of the slug bubbles as well as the bed height, and a slight decrease in the slug frequency. The results are presented in a level of detail suitable for comparison with later numerical simulation.     

Gold Nitride: Preparation and Properties

We review the currently known methods of producing gold nitride and report on the influence of electrically isolated substrates on the growth of gold nitride films by reactive ion sputtering (RIS). It is found that isolation of the substrate decreases grain size and increases nitrogen content, the latter attributed to longer nitrogen ion lifetime on the surface of the growing film. The chemical reactivity of gold nitride is compared with that of pure gold films using the adsorption of 1-dodecyl mercaptan (CH₃(CH₂)₁₁SH) as a model system and it is found that there is no significant difference between gold films and gold nitride in terms of Au–S binding. However, gold nitride nanoparticles are suggested to be worthy of further investigation in terms of their catalytic properties.