Ionic and molecular diffusion in cementitious materials

The work described in this thesis is an attempt to provide improved understanding of the effects of several factors affecting diffusion in hydrated cement pastes and to aid the prediction of ionic diffusion processes in cement-based materials. Effect of pore structure on diffusion was examined by means of comparative diffusion studies of quaternary ammonium ions with different ionic radii. Diffusivities of these ions in hydrated pastes of ordinary portland cement with or without addition of fly ash were determined by a quasi-steady state technique. The restriction of the pore geometry on diffusion was evaluated from the change of diffusivity in response to the change of ionic radius. The pastes were prepared at three water-cement ratios, 0.35, 0.50 and 0.65. Attempts were made to study the effect of surface charge or the electrochemical double layer at the pore/solution interface on ionic diffusion. An approach was to evaluate the zeta potentials of hydrated cement pastes through streaming potential measurements. Another approach was the comparative studies of the diffusion kinetics of chloride and dissolved oxygen in hydrated pastes of ordinary portland cement with addition of 0 and 20% fly ash. An electrochemical technique for the determination of oxygen diffusivity was also developed. Non-steady state diffusion of sodium potassium, chloride and hydroxyl ions in hydrated ordinary portland cement paste of water-cement ratio 0.5 was studied with the aid of computer-modelling. The kinetics of both diffusion and ionic binding were considered for the characterization of the concentration profiles by Fick's first and second laws. The effect of the electrostatic interactions between ions on the overall diffusion rates was also considered. A general model concerning the prediction of ionic diffusion processes in cement-based materials has been proposed.

Concurrent multiscale modelling of atomistic and hydrodynamic processes in liquids

Fluctuations of liquids at the scales where the hydrodynamic and atomistic descriptions overlap are considered. The importance of these fluctuations for atomistic motions is discussed and examples of their accurate modelling with a multi-space-time-scale fluctuating hydrodynamics scheme are provided. To resolve microscopic details of liquid systems, including biomolecular solutions, together with macroscopic fluctuations in space-time, a novel hybrid atomistic-fluctuating hydrodynamics approach is introduced. For a smooth transition between the atomistic and continuum representations, an analogy with two-phase hydrodynamics is used that leads to a strict preservation of macroscopic mass and momentum conservation laws. Examples of numerical implementation of the new hybrid approach for the multiscale simulation of liquid argon in equilibrium conditions are provided. © 2014 The Author(s) Published by the Royal Society.

ICT innovation diffusion in small logistics service providers:an empirical study

For companies competing in highly dynamic markets, innovation is considered a fundamental component of a successful business as it allows companies to sustain profit margins, sales growth and reduce competitors’ pressures. Information and communication technology (ICT) is essential innovation enablers especially in service companies. The focus of the paper is on the analysis of the role of ICT in innovation processes of small third-party logistics service providers (3PLs). On the basis of quantitative evidence emerging from a recent survey carried out on the Italian 3PL market, the paper analyses how ICT is used to support innovation and the factors the inhibit/facilitate the usage of ICT in such companies. Implications for supply chain innovation management are derived from the research and managerial perspectives.

Discrete Models of Time-Fractional Diffusion in a Potential Well

Mathematics Subject Classification: 26A33, 45K05, 60J60, 60G50, 65N06, 80-99.

Four methods for measuring the solubilities of gases and vapors in liquids and polymers

Peer reviewed

Four methods for measuring the solubilities of gases and vapors in liquids and polymers

Peer reviewed

Digitally Mediated Political Participation: Understanding the Democratic Impact of Internet Diffusion in the Asian Media Systems

Thesis (Ph.D.)--University of Washington, 2016-08

Convection-diffusion in MHD: Comparison of primitive variable and vector potential solutions of the magnetic induction equation

Abstract not available