Implementation of Porous Media Formulation for Geomaterials

The mechanical behavior of saturated geomaterials is largely governed by the interaction of the solid skeleton with the fluids present in the pore structure. Traditional geotechnical analyses, commonly based on simplified effective stress theories, fail to fully describe the behavior of saturated porous materials. Hence, it has become necessary to use more robust and complete formulations. In this context, the use of multiphase theories appears to be an alternative and more appropriate approach. In this work, the governing equations of a porous media interacting with immiscible porous fluids are presented in the light of the theory of mixtures. A generalized Galekin procedure is devised to establish the coupled mixed finite-element equation set with u-p-U form. An unconditionally stable implicit solution procedure is used for the time domain numerical solution. Finally, a recently developed constitutive model based on the fuzzy set plasticity concept is described and implemented in the finite-element tool. A companion paper focuses on applications of this theory, and case studies are used to evaluate the proposed formulation.     

The relationship of style difficulty, practice, and ability to efficiency of reading and to retention.

Two groups of Ss, one of high and one of low mechanical ability, read a technical passage before an eye-movement camera. An "easy" style and a "hard" style passage were used, and Ss read the passage once or three times. Reading efficiency measures collected were words read per second and per fixation; retention measures were scores on modified recall and word recognition tests. The high ability group scored better on all measures than the low ability group; three readings yielded superior scores on the retention measures; and the "easy" style gave higher scores on the reading efficiency and modified recall measures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Characterization of polyaniline via pyrolysis mass spectrometry

In this work, direct insertion probe pyrolysis mass spectrometry technique was applied to investigate the thermal and the structural characteristics of electrochemically prepared HCl and HNO₃‐doped polyaniline (PANI) films. It has been determined that the thermal degradation of both samples showed three main thermal degradation stages. The first stage around 50–60°C was associated with evolution of solvent and low‐molecular‐weight species adsorbed on the polymer, the second stage just above 150°C was attributed to evolution of dopant‐based products, and the final degradation stage at moderate and elevated temperatures was associated with evolution of degradation products of the polymer. Chlorination and nitrolysis of aniline during the electrochemical polymerization were detected. Extent of substitution increased as the electrolysis period was increased. Furthermore, for the HNO₃‐doped PANI, the evolution of CO₂ at elevated temperatures confirmed oxidation of the polymer film during electrolysis. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Expansion characteristics of a nutritious extruded snack food using response surface methodology

Response surface methodology was used to analyze the effect of screw speed (220–340 rpm), feed moisture (11.0–15.0%, wet basis) and feed rate (22.0–26.0 kg/h, wet basis) on the physical properties (i.e., bulk density, expansion, porosity) of a nutritionally balanced extruded snack food. Regression equations describing the effect of each variable on the responses were obtained. Responses were most affected by changes in screw speed followed by feed moisture and feed rate (P<0.05). Expansion and porosity increased with screw speed and feed moisture whereas the opposite was observed for bulk density. Radial expansion was found to be a better index to measure the extent of expansion than the axial and overall expansions, indicated by a higher correlation coefficient.     

Chitosan microspheres and sponges: Preparation and characterization

In this study, chitosan microspheres and sponges were prepared and characterized for diverse biomedical applications successfully. The chitosan microspheres were obtained with a “suspension crosslinking technique” in the size range of 30–700 μm. The stirring rate of the suspension medium and the chitosan/acetic acid ratio, emulsifier, and crosslinker, that is, the glutaraldehyde concentration in the suspension medium, were evaluated as the effective parameters on the size/size distributions of the microspheres. The microsphere size/size distributions were increased with the decreasing of all effective parameters except the chitosan/acetic acid ratio. In the second part of the study, chitosan sponges were prepared with a solvent‐evaporation technique and sponges were cross‐linked either during the formation or after the formation of sponges by using a cross‐linker, that is, glutaraldehyde. When the sponges were crosslinked during the formation, fibrillar structures were obtained, while the leaflet structures were obtained in the case of crosslinking after the formation of sponges. In the last part of the study, the swelling behavior of both the chitosan microspheres and sponges were evaluated using different amounts of the crosslinker. The swelling ratio was increased in both types of structures, that is, microspheres and sponges, by decreasing the amount of the crosslinker. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 76: 1637–1643, 2000