27,139 research outputs found
Sampling power-law distributions
No full textPower-law distributions describe many phenomena related to rock fracture. Data collected to measure the parameters of such distributions only represent samples from some underlying population. Without proper consideration of the scale and size limitations of such data, estimates of the population parameters, particularly the exponent D, are likely to be biased. A Monte Carlo simulation of the sampling and analysis process has been made, to test the accuracy of the most common methods of analysis and to quantify the confidence interval for D. The cumulative graph is almost always biased by the scale limitations of the data and can appear non-linear, even when the sample is ideally power law. An iterative correction procedure is outlined which is generally successful in giving unbiased estimates of D. A standard discrete frequency graph has been found to be highly inaccurate, and its use is not recommended. The methods normally used for earthquake magnitudes, such as a discrete frequency graph of logs of values and various maximum likelihood formulations can be used for other types of data, and with care accurate results are possible. Empirical equations are given for the confidence limits on estimates of D, as a function of sample size, the scale range of the data and the method of analysis used. The predictions of the simulations are found to match the results from real sample D-value distributions. The application of the analysis techniques is illustrated with data examples from earthquake and fault population studies
Pickering polymerized high internal phase emulsions: fundamentals to advanced applications
No full textPickering-polymerized high internal phase emulsions have attracted attention since their successful first preparation 15 years ago, primarily due to their large pores and potential for functionalization during production. This review elucidates the fundamental principles of Pickering emulsions, Pickering HIPEs, and Pickering PolyHIPEs while comparing them to conventional surfactant-stabilized counterparts. The morphology of Pickering PolyHIPEs, with particular emphasis on methods for achieving interconnected structures, is explored and critically assessed. Lastly, the mechanical properties and diverse applications of these materials are reviewed, highlighting their use as catalytic supports and sorbent materials. The study aims to guide both new and experienced researchers in the field by comprehensively addressing the current potential and challenges of Pickering PolyHIPEs. Once the mystery behind the closed cellular pores of Pickering PolyHIPEs is resolved, these materials are expected to become more popular, particularly in applications where mass transfer is critical, such as tissue engineering
Immobilising oils in geopolymer cements using pickering emulsions
No full textSilica fume was investigated as a potential Pickering agent as an alternative route of immobilisation of organic oils (Nevastane oil or TPB/dodecane) in potassium geopolymer cement. The Pickering emulsion was able to immobilise up to 30 wt% Nevastane loading in the geopolymer cement. The formation of the Pickering emulsion was able to decrease the initial and final setting times, whilst, increasing the early compressive strength of the Pickering samples in comparison to non-emulsified Nevastane samples. The X-ray tomography data further showed the successful dispersion of the Nevastane droplets throughout the geopolymer matrix, with good uniformity of the droplet distribution. However, the Pickering emulsion was unable to successfully immobilise the TBP/dodecane at any weight loading, suggesting that this immobilisation route was not suitable for this particular organic oil. Hence, Pickering emulsions could be used as an alternative route for the immobilisation of selected organic oils into geopolymer cements
Enzymatically produced nanocellulose as emulsifier for Pickering emulsion
No full textWith the increasing demand for label-friendly emulsion products, chemical treatments and the addition of non-natural ingredients are inadvisable in food, cosmetic, and pharmaceutical sectors. The current research proposed a green development strategy from nanocellulose production to emulsion preparation, i.e., enzymatically prepared nanocellulose (ENC) for stabilizing O/W Pickering emulsions. Benefiting from a mild enzymatic reaction, ENC inherently had low Zeta potential and oil/water interfacial tension, facilitating the formation of stable Pickering emulsions. Biphasic fluorescence staining, emulsion polymerization, and rheology were employed to investigate the emulsification characteristics of ENC, establishing the interfacial adsorption behavior and concentration-dependent phase behavior of ENC-stabilized Pickering emulsions. Importantly, due to strong particle-particle and interface-particle interactions dominated by van der Waals forces and hydrogen bonding, ENC-stabilized Pickering emulsions exhibited excellent stability under different temperatures, pH values, NaCl concentrations, and centrifugation. This work provides a green pathway for the development of nanocellulose-based Pickering emulsions
Interparticle photo-cross-linkable Pickering emulsions for rapid manufacturing of complex-structured porous ceramic materials
No full textA new series of Pickering emulsions that can be photo-cured by interparticle photo-cross-linking reactions using small amounts of multifunctional acrylate (MA) monomers is proposed to rapidly manufacture complex-structured porous ceramic materials. In our new process, water in oil (w/o) Pickering emulsion was designed by vigorous mixing of water and polyethyleneimine partially complexed with oleic acid (PEI-OA)-stabilized SiO2/toluene suspension containing small amounts of MA and a photo radical initiator. Ultraviolet light irradiation to this w/o Pickering emulsion induced the formation of interparticle photo-crosslinks, which resulted in successful photocuring by photo-radical polymerization of MA and the Michael addition reaction between the polymerized MA and PEI-OA on the particles in the oil phase. We further applied the newly designed photo-curable Pickering emulsion and demonstrated that SiO2 components with pores related to the dispersed aqueous phase and complexed outer structures could be shaped via silicone molding or a hybridized approach of photocuring and green machining. Because of the reduced amounts of MA used, the porous SiO2 green components could be heat-treated using rapid heating profiles without any structural collapse for dewaxing and partial sintering. (C) 2022 The Society of Powder Technology Japan. Published by Elsevier BV and The Society of Powder Technology Japan. All rights reserved
Asymptotic behavior of <em>BV</em> functions and sets of finite perimeter in metric measure spaces
No full textAbstractIn this paper, we study the asymptotic behavior of BV functions in complete metric measure spaces equipped with a doubling measure supporting a 1-Poincaré inequality. We show that at almost every point x outside the Cantor and jump parts of a BV function, the asymptotic limit of the function is a Lipschitz continuous function of least gradient on a tangent space to the metric space based at x.We also show that, at co-dimension 1 Hausdorff measure almost every measure-theoretic boundary point of a set (Ε) of finite perimeter, there is an asymptotic limit set Ε∞ corresponding to the asymptotic expansion of Ε and that every such asymptotic limit (Ε)∞ is a quasiminimal set of finite perimeter. We also show that the perimeter measure of Ε∞ is Ahlfors co-dimension 1 regular. Abstract
In this paper, we study the asymptotic behavior of BV functions in complete metric measure spaces equipped with a doubling measure supporting a 1-Poincaré inequality. We show that at almost every point x outside the Cantor and jump parts of a BV function, the asymptotic limit of the function is a Lipschitz continuous function of least gradient on a tangent space to the metric space based at x.We also show that, at co-dimension 1 Hausdorff measure almost every measure-theoretic boundary point of a set (Ε) of finite perimeter, there is an asymptotic limit set Ε∞ corresponding to the asymptotic expansion of Ε and that every such asymptotic limit (Ε)∞ is a quasiminimal set of finite perimeter. We also show that the perimeter measure of Ε∞ is Ahlfors co-dimension 1 regular
Self-assembled graphene oxide microcapsules in Pickering emulsions for self-healing waterborne polyurethane coatings
No full textA self-assembly process was employed to prepare the graphene oxide microcapsules (GOMCs), containing linseed oil as the healing agent. The nanometer-thick shells of GOMCs were built by the liquid crystalline assembling of graphene oxide (GO) sheets, forming at liquid liquid interface in Pickering emulsions. The GOMCs were embedded into waterborne polyurethane matrix, enabling the facile fabrication of self-healing composite coatings on hot-dip galvanized steel surfaces. The inclusion of GOMCs in the composite coatings not only imparted self-healing properties to the coatings, but also improved their anticorrosion properties because of the physical barrier of the GO shell, leading to much better survival to the weather/marine environment and surface wear. (C) 2017 Elsevier Ltd. All rights reserved
Stabilization of ginger essential oil Pickering emulsions by pineapple cellulose nanocrystals
No full textPickering emulsions (PE) are systems made up of two incompatible fluids, these are stabilized by solid organic or inorganic particles located on their interface. Cellulose nanocrystals (CNCs) are sustainable and biocompatible value-added naturally occurring biomolecules which are being investigated as PE stabilizers in the cosmetic, food, and pharmaceutical industries. The objective of this research was to investigate the efficacy of pineapple cellulose nanocrystals as stabilizers for a ginger essential oil-in-water Pickering emulsion. Anionic pineapple cellulose nanocrystals were prepared by acid hydrolysis. Ginger essential oil-in-water emulsions were prepared by ultrasonication. Pineapple CNC produced stable Pickering emulsions with surface average droplet size of 4.3 μm–6.2 μm, high negative zeta potential, high viscosity, and high adsorption at the interface. Pickering emulsions by ultrasonication were stable against droplet coalescence, phase separation, and droplet flocculation for at least 8 weeks at 25 °C or 40 °C at various droplet sizes. The emulsion droplet size and volume density (droplet size distribution) were evaluated by varying the particle concentration (CNC 0.25 g/100 ml or 0.50 g/100 ml) and/or oil fraction (10–20 g/100 ml). At constant oil fraction, the emulsion viscosity increased as the nanocrystal concentration increased. The cellulose nanocrystal-stabilized ginger oil-Pickering emulsions exhibited shear-thinning characteristics of a pseudo-plastic fluid. Pineapple nanocellulose crystal -stabilized ginger oil-Pickering emulsions exhibited high stability with a creaming index of zero. CNC was found to be an effective Pickering stabilizer for oil-in-water emulsions in various food applications
Characterization of the compact operators on the class (bv,bvkθ)
No full textThe space bv, the set of all bounded variation sequences, has an important role in the summability theory. In recent study, this spaces has been extended to the space bvk? and some matrix class on this space has been characterized [2]. In the present paper, for 1 ? k ?, computing Hausdorff measure of non-compactness, we characterize compact operators in the class (bv, bvk?), where ? is a sequence of positive numbers. © 2019 Author(s)
A lower semicontinuity result for functionals on BV.
No full textIn this work the author deals with some very important problems in the calculus of variations related to the functional|
that can be considered as the natural extension to BV(Ω) of the functional
f(x,u,Du)dx, u ∈ W1,1(Ω) [see G. Dal Maso, Manuscripta Math. 30 (1979/80), no. 4, 387–416; MR0567216]. The author generalizes her results from another paper [Boll. Un. Mat. Ital. B (7) 5 (1991), no. 2, 291–313] and proves that F is lower semicontinuous, along sequences bounded in BV(Ω), relative to the strong topology of L1(Ω). The interest of the result is based on two facts: (i) the integrand f(x,s,p) is dependent on x, while in the above-mentioned paper by the author it was not so; (ii) the integrand f (x, s, p), which was supposed in Dal Maso’s paper [op. cit.] to be lower semicontinous relative to s, is not so in the present paper
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