Impact of cellulose nanocrystal aspect ratio on crystallization and reinforcement of poly(butylene adipate‐co‐terephthalate)

Cellulose nanocrystals (CNCs) are appealing nanomaterials for the reinforcement of polymeric materials. It is now well established that high mechanical properties are obtained when preparing the nanocomposite by casting/evaporation methods and using CNC contents above the percolation threshold. This phenomenon results from the formation of a stiff CNC network within the matrix meaning that the properties of the matrix play only a limited role on the mechanical properties of the material when the matrix is in the rubbery state. In subpercolation concentration or when using a different processing technique, the level of understanding is less clear, mainly when the CNC‐induced crystallization of the matrix interferes with the reinforcing mechanism. In this study, we used CNCs with different aspect ratios to prepare nanocomposites by extrusion with polybutyrate adipate terephthalate as matrix. The impact of CNC on the crystallinity of the matrix and mechanical properties of the nanocomposite has been investigated. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 2284–2297     

Extending and relating different approaches for solving fuzzy quadratic problems

Quadratic programming problems are applied in an increasing variety of practical fields. As ambiguity and vagueness are natural and ever-present in real-life situations requiring solutions, it makes perfect sense to attempt to address them using fuzzy quadratic programming problems. This work presents two methods used to solve linear problems with uncertainties in the set of constraints, which are extended in order to solve fuzzy quadratic programming problems. Also, a new quadratic parametric method is proposed and it is shown that this proposal contains all optimal solutions obtained by the extended approaches with their satisfaction levels. A few numerical examples are presented to illustrate the proposed method.     

A diffusive logistic equation with concentrated and nonlocal sources

In this paper, we study a reaction‐diffusion equation where nonlinear memory and concentration effects are considered at the same time. We are specially concerned with the local solvability of this problem for singular initial data in Lebesgue spaces. We also analyze the vanishing concentration problem and prove a blow‐up alternative. Copyright © 2017 John Wiley & Sons, Ltd.     

Isotopic dependence of the nuclear charge radii and binding energies in the relativistic Hartree-Fock formalism

Relativistic nonlinear models based on the Hartree and Hartree-Fock approximations, including the σ, ω, π, and ρ mesons, are worked out to explore the behavior of the nuclear charge radii and the binding energies of several isotopic chains. We find a correlation between the magnitude of the anomalous kink effect (KE) in the Pb isotopic family and the compressibility modulus (K) of nuclear matter. The KE appears to be sensitive, in particular, to the mechanisms which control the K value. The influence of the symmetry energy on the Ca isotopic chain is also studied. The behavior of the charge radii of single-particle states for some special cases and its repercussion on the nuclear charge radius is analyzed. The effect of pairing correlations on the models improves considerably the quality of the results in both binding energy and KE.     

Characterization by proper-orthogonal-decomposition of the passive controlled wake flow downstream of a half cylinder

This study focuses on the flow modifications generated by a flat plate stabilizer placed downstream of a half-cylinder compared to the wake formation without the plate. For moderate Reynolds number, a snapshot proper-orthogonal-decomposition method based on particle-image-velocimetry (PIV) is used to analyze the complex dynamics of the flows and to highlight typical swirl formation mechanisms. Using this tool, the near-wake structures, the kinetic aspects, the energy contributions, the degree of organization of the structures and their temporal behaviour are identified. A strong link between the Strouhal number, the mean vorticity and the Total Energy is observed. The interference of the shear layer with the stabilizer has an atypical influence on the wake characteristics.     

Macroscopic capillary pressure

The macroscopic pressure difference between two immiscible, incompressible fluid phases flowing through homogeneous porous media is considered. Starting with the quasi-static motions of two compressible fluids, with zero surface tension, it is possible to construct a complete system of equations in which all parameters are clearly defined by physical experiments. The effect of surface tension is then formally included in the definition of the specific process under consideration. Incorporating these effects into the pressure equations and taking the limit as compressibilities go to zero, the independent pressure equations are shown to yield indeterminate forms. However, the difference of the two pressure equations is found to yield a new process-dependent dynamical equation.List of Symbols J LeverettJ function - K _i bulk modulus of fluidi (i=1, 2) - K _s bulk modulus of solid - K permeability - P fractional porosity of the wetting phase (in LeverettJ function) - p _i macroscopic pressure of fluidi (i=1, 2) - Q _ij Mobilities (i, j=1, 2) (cf. de la Cruz and Spanos, 1983) - V _i macroscopic velocity vector of fluidi (i=1, 2) Greek Letters surface tension - _i compliance factor for fluidi (i=1, 2) for incompressible flow defined in equations (29) and (30) (process-dependent) - compliance factor for the flow of two incompressible fluid (cf. eqns. (32) and (33) for relation to _i) - _i compliance factor for a compressible fluid (i=1, 2) (process-dependent) (cf. de la Cruzet al., 1989, 1993) - _i modification to static compliance factor for fluidi (i=1, 2) as a result of quasi-static flow - _i fraction of space occupied by fluidi (i=1, 2) measured dynamically - _i ^o fraction of space occupied by fluidi (i=1, 2) measured statically - _i shear viscosity of fluidi (i=1, 2) - _i bulk viscosity of fluidi (i=1, 2) - _i density of fluidi (i=1, 2)     

An analysis of the viability of polymer flooding as an enhanced oil recovery technology

The concept of improving oil recovery through polymer flooding is analysed. It is shown that while the injection of a polymer solution improves reservoir conformance, this beneficial effect ceases as soon as one attempts to push the polymer solution with water. Once water injection begins, the water quickly passes through the polymer creating a path along which all future injected water flows. Thus, the volume of the polymer slug is important to the process and an efficient recovery would require that the vast majority of the reservoir be flooded by polymer. It is also shown that the concept of grading a polymer slug to match the mobilities of the fluids at the leading and trailing edges of a polymer slug does not work in a petroleum reservoir. While this process can supply some additional stability to the slug, it is shown that for the purposes of enhanced oil recovery this additional stability is not great enough to be of any practical use. It is found that in this case the instability has simply been hidden in the interior of the slug and causes the same sort of instability to occur as was the case for the uniform slug.