Osmotic and Activity Coefficients of {yKCl+(1−y)MgCl2}(aq) at T=298.15 K

Isopiestic vapor-pressure measurements were made at the temperature 298.15 K for aqueous KCl + MgCl₂ solutions using KCl(aq) as the reference standard. The measurements for these ternary solutions were made at KCl ionic strength fractions of y=0.0, 0.1989, 0.3996, 0.5993, 0.7925 and 1.0 (with two additional sets at y=0.0, 0.2021, 0.3998, 0.6125, 0.8209 and 1.0) for the ionic strength range from 0.4014 to 6.2790 mol?kg^?1. Our results, and those from two previous isopiestic studies, were combined and used with previously determined parameters for KCl(aq) and those determined here for MgCl₂(aq) to evaluate mixing parameters for the Clegg-Pitzer-Brimblecombe model. These combined data were also used to determine the mixing parameters of the Scatchard model. Both sets of model parameters are valid for ionic strengths of I≤12.8 mol?kg^?1, where higher-order electrostatic effects have been included in the Clegg-Pitzer-Brimblecombe mixture model. The activity coefficients for KCl and MgCl₂ were calculated from these models and the results for KCl were compared to experimental data from Emf measurements. The Scatchard model interaction parameters were used for calculation of the excess Gibbs energy as a function of the ionic strength and ionic strength fraction of KCl. The Zdanovskii-Robinson-Stokes rule of linearity for mixing of isopiestic solutions was tested.     

Singular fractional evolution differential equations

We give an existence-uniqueness result for linear and nonlinear time fractional evolution equations with singularities in corresponding norm in extended Colombeau algebra of generalized functions using fractional analog for Duhamel principle. Paper deals with some nonlinear models with singularities appearing in viscoelasticity and in anomalous processes which have met great interest among researchers who consider them as a challenge in recent years.     

On the extremal geometric–arithmetic graphs with fixed number of vertices having minimum degree

Annals of Operations Research - The geometric–arithmetic index GA of a graph is defined as sum of weights of all edges of graph. The weight of one edge is quotient of the geometric and...     

Multiscale characterization of antimicrobial poly(vinyl butyral)/titania nanofibrous composites

Titania nanofillers were used to reinforce nanofibers in composite mats produced by electrospinning of poly(vinyl butyral) with two different concentrations of polymers. The titania nanoparticles and titania nanotubes were added into an acetic acid/ethanol solution in different contents of 3 and 1 wt%, respectively. The effect of the processing system on the morphology of the produced fibers was analyzed. The antimicrobial poly(vinyl butyral) composite fibers with titanium dioxide nanoparticles and titanium dioxide nanotubes were produced by single and multineedle electrospinning systems. This study reports fabrication of composite nanofibrous mats with significant mechanical and antimicrobial properties at a high production speed, which is promising for commercial applications (health care, photocatalysis, protective clothing, etc.). The reported result revealed an outstanding correlation between values of elastic modulus derived from nanoindentation and dynamic mechanical techniques. Copyright © 2017 John Wiley & Sons, Ltd.     

Optimal damping control and nonlinear parabolic systemes

An optimal control problem for a parabolic equation when the control parameter is the zero order coefficient of the differential operator is considered. An optimality system is derived. Under a certain sign condition, the problem is solved completely, by proving uniqueness and providing a constructive existence proof for the nonlinear parabolic optimality system.