4,376 research outputs found
Comment on ``Method to analyze electromechanical stability of dielectric elastomers" [Appl. Phys. Lett. 91, 061921 (2007)]
The model of Zhao and Suo can be readily generalized to predict the critical
breakdown electric field value of elastomers with arbitrary elastic
strain energy function. An explicit expression for is presented for
elastomeric thin films under biaxial strain and comparisons are made with
experimental data using a two term Ogden rubber elasticity model. Simplified
results for uniaxial and for equi-biaxial stress provide further insight into
the findings of Zhao and Suo.Comment: 2 page
Towards the implementation of an ion-exchange system for recovery of fluoride commodity chemicals. Kinetic and dynamic studies
Spent potlining (SPL), a hazardous waste product from primary aluminium production, presents an important opportunity to recycle fluoride and conserve global fluorspar reserves. A novel strategy for treatment of the waste requires a selective fluoride-removal step from aqueous leachate. This has been demonstrated, using a Lanthanum-loaded chelating resin, in a series of kinetic and dynamic studies, with a view to industrial implementation. Kinetics could be described by the pseudo second-order model and uptake from SPL leachate was considerably higher than from equivalent NaF solutions, although observed rate constants were an order of magnitude less. Uptake of coexisting species and activation energy calculations indicated that a novel complexation interaction between La centres and aqueous aluminium hydroxyfluorides dominated the uptake process. The resin operated efficiently in column studies, with a dynamic fluoride uptake capacity of 66.7 mg g-1, calculated by the Dose-Response model, which produced the best fit to the data. The attained elution profile suggested that fluoride recovery by cryolite precipitation would be feasible, which could be recycled back into primary aluminium production or exploited as a commodity. The resin was found to have high durability in performance studies over repeated batch treatments
Selective environmental remediation of strontium and cesium using sulfonated hypercrosslinked polymers (SHCPs)
Sulfonated hypercrosslinked polymers based on 4,4’-bis(chloromethyl)-1,1’-biphenyl (BCMBP) were synthesized via metal-free (SHCP-1) and conventional Lewis acid-catalyzed (SHCP-2) Friedel-Crafts alkylation routes. The sulfonated polymers possessed BET surface areas in excess of 500 m2 g-1. SHCP-1 was investigated for its ability to extract Sr and Cs ions from aqueous solutions via the ion-exchange reaction of the sulfonic acid moiety. Equilibrium uptake data could be accurately modelled by the Dubinin-Radushkevich isotherm, with maximum calculated loading values of 95.6 ± 2.8 mg g-1 (Sr) and 273 ± 37 mg g-1 (Cs). Uptake of both target ions was rapid, with pseudo 2nd-order rate constants calcu-lated as 7.71 ± 1.1 (x 10-2) for Sr and 0.113 ± 0.014 for Cs. Furthermore, the polymer was found to be selective towards the target ions over large excesses of naturally occurring competing metal ions such as Na and K. We conclude that hyper-crosslinked polymers may offer intrinsic advantages over other adsorbents for the remediation of aqueous Sr and Cs contamination
Group Dynamics of Zebra and Wildebeest in a Woodland Savanna: Effects of Predation Risk and Habitat Density
.Using generalized linear models, we examined the relative importance of habitat type (differing in vegetation density), probability of encountering lion (based on utilization distribution of all individual lions in the reserve), and season in predicting group size and composition. We found that only in open scrub habitat, group size for both ungulate species increased with the probability of encountering lion. Group composition differed between the two species and was driven by habitat selection as well as predation risk. For both species, composition of groups was, however, dominated by males in open scrub habitats, irrespective of the probability of encountering lion.Distribution patterns of wildebeest and zebra groups at the landscape level directly support the theoretical and empirical evidence from a range of taxa predicting that grouping is favored in open habitats and when predation risk is high. Group composition reflected species-specific social, physiological and foraging constraints, as well as the importance of predation risk. Avoidance of high resource open scrub habitat by females can lead to loss of foraging opportunities, which can be particularly costly in areas such as KGR, where this resource is limited. Thus, landscape-level grouping dynamics are species specific and particular to the composition of the group, arising from a tradeoff between maximizing resource selection and minimizing predation risk
Energy Spectrum Evolution of a Diffuse Field in Elastic Body Caused by Weak Nonlinearity
We study the evolution of diffuse elastodynamic spectral energy density under
the influence of weak nonlinearity. It is shown that the rate of change of this
quantity is given by a convolution of the linear energy at two frequencies.
Quantitative estimates are given for sample aluminum and fused silica blocks of
experimental interest.Comment: 9 pages, 3 figures; revised for better presentatio
The Cauchy problem for a class of two-dimensional nonlocal nonlinear wave equations governing anti-plane shear motions in elastic materials
This paper is concerned with the analysis of the Cauchy problem of a general
class of two-dimensional nonlinear nonlocal wave equations governing anti-plane
shear motions in nonlocal elasticity. The nonlocal nature of the problem is
reflected by a convolution integral in the space variables. The Fourier
transform of the convolution kernel is nonnegative and satisfies a certain
growth condition at infinity. For initial data in Sobolev spaces,
conditions for global existence or finite time blow-up of the solutions of the
Cauchy problem are established.Comment: 15 pages. "Section 6 The Anisotropic Case" added and minor changes.
Accepted for publication in Nonlinearit
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