Algebraic preconditioning for Biot-Barenblatt poroelastic systems

Poroelastic systems describe fluid flow through porous medium coupled with deformation of the porous matrix. In this paper, the deformation is described by linear elasticity, the fluid flow is modelled as Darcy flow. The main focus is on the Biot-Barenblatt model with double porosity/double permeability flow, which distinguishes flow in two regions considered as continua. The main goal is in proposing block diagonal preconditionings to systems arising from the discretization of the Biot-Barenblatt model by a mixed finite element method in space and implicit Euler method in time and estimating the condition number for such preconditioning. The investigation of preconditioning includes its dependence on material coefficients and parameters of discretization.     

Influence of ion bombardment on growth and properties of PLD created DLC films

A hybrid PLD system with ion bombardment of films was developed. Growing DLC films were modified during the laser deposition (10 J?cm^?2) by argon ions with energy in the range from 40 eV to 210 eV and cathode current of 0.15 A and 0.5 A. The content of sp² “graphitic” and sp³ “diamond” bonds was measured using XPS. Sp³ bonds changed from 60 % to 81 %. We found the highest sp³ content for energy of 40 eV. Hardness (and reduced Young’s modulus) were determined by nanoindentation and reached 49 GPa (277 GPa). Film adhesion was studied using the scratch test and was up to 14 N for titanium substrates. Relations among deposition conditions and measured properties are presented.     

A simple-minded direct approach to estimating the calibration parameter for proportionate data

In non-destructive assay there exist techniques founded on physics principles and experimental design for which the quantity of interest y_True to be estimated is expected to vary in direct proportion to the true value x_True of the experimentally observed predictor quantity x. In other words, the calibration is a straight line passing through the origin, so that the assay method is fully described by a single parameter, the slope. In principle a single reference item is sufficient to estimate the slope. However, there are good reasons for including more than a single item in the calibration procedure. When multiple items are used questions arise regarding how to make best use of all the available calibration data in estimating the slope. This paper shows that the usual weighted least squares curve fitting approach can be circumvented by using only the familiar notion of a weighted arithmetic mean. In particular we draw attention to the ease with which uncertainties in both x and y can be incorporated using this simple and direct approach. Moreover the uncertainty in the calibration parameter is estimated using familiar techniques and with an appropriate magnitude for subsequent use, for instance, in setting reasonable uncertainties on assay results performed using the calibration. For completeness, weighted least squares accounting for nonzero covariances among the measurements y of y_True together with an errors in predictors approach accounting for errors in x is also presented.     

Carboxymethylated nanofibrillated cellulose: effect of monovalent electrolytes on the rheological properties

The effect of the ionic strength on the properties of a carboxymethylated nanofibrillated cellulose (NFC) system was investigated through rheological studies. It was shown that homogenization of pulp suspensions containing a high amount of a monovalent electrolyte leads to the production of NFC systems displaying a lower magnitude in the rheological response as compared with systems prepared at lower ionic strengths conditions. It was further shown that increasing the ionic strength of NFC suspensions after their manufacturing also results in a lowering of the rheological response. The decreased rheological response in the former case was postulated to be caused by a lowering of the delamination deficiency of the homogenization process, due to decreased swelling of the carboxymethylated pulp, caused by the screening of the charges. In the latter case (post-addition of the electrolyte), the lowering of the rheological response was postulated to be due to the compression of the electrostatic double layer, when the electrostatic repulsion between the charged fibrils diminished in the presence of the electrolyte.     

Mathematical Modeling of Tidal Effects in Groundwater

This paper presents a special use of the linear poroelasticity theory to describe tidally induced groundwater oscillations. Two models of oscillation inducing mechanism make use of this theory to predict groundwater level fluctuations. The numerical solutions of both models are presented and compared with well water level measurement obtained in Police Basin, north-east Bohemia.