A Phase Field Crystal Study of Freezing and Melting

Though melting is a common phase transition in nature, the small scale details of the crystal breakdown in two dimensions are not yet fully understood. We present a numerical investigation of melting and freezing in two dimensions through the phase field crystal model. We start out by discussing phase transitions by means of disorder-order transitions through the phase field method. The method is suitable of describing phase transitions in heterogeneous and isotropic systems and is an important tool for modeling micro structural evolution. We continue by deriving the phase field crystal method. That is a method in which the isotropic approximation is relaxed and the free energy functional is constructed to ensure a periodic structure in the equilibrium state. By this approach, important features such as crystal orientation, defects and deformations are naturally incorporated in the model. Hence, this method provides a suitable method for describing the process of crystal growth as well as the breakdown of the crystalline structure, that is the processes of freezing and melting respectively. Additionally, a set of amplitude equations are presented for the study of the dynamical evolution in the crystalline phase. Thereafter, we discuss the process of melting and the role of dimensionality and dislocations in the phase transition. We limit our work to two dimensional systems and investigate the evolution of melting numerically with a particular focus on the role of defects in the phase transition. The simulated melting is induced by two different protocols, that is uniform heating and applied shear stress, and we evaluate our numerical results relative to the theory of dislocation mediated melting. As a closure we summarize our results, elaborate upon the challenges in the search for the melting mechanism and propose ideas for future work which can be carried through with the phase field crystal method

The Surfaces of Titanate Minerals, Ceramics and Silicate Glasses: Surface Analytical and Electron Microscope Studies

The review evaluates evidence of aqueous surface attack on glasses, titanate minerals and synthetic rock material (Synroc C) available from:- leach rates; surface analysis (XPS, SAM, SIMS); IR spectroscopy; and electron microscopy. Direct observations are described showing the formation of:- ion-exchanged, cation deficient layers; altered glass network and crystal line lattice layers and recrystallised, reprecipitated and surface-segregated layers. The titanate minerals react in the order perovskites \u3e hollandite \u3e fluorite structures (zirconolite, zirkelite, pyrochlore, polymigllyte) \u3e rutile. The formation of amorphous Ti-O films, recrystallising to TiO2 (anatase and brookite), is observed on perovskite and hollandite surfaces. The surface reactivity of the titanate minerals is essentially the same in the ceramic assemblage Synroc C but additional microstructure (intergranular films, pores, triple points, minor phases) complicates the interpretation of first-day leach rates and depth profiles of leached discs. Reinterpretation of apparently congruent and incongruent dissolution data, using this evidence, is given for the glasses and titanate minerals. It is shown that solution analyses do not adequately describe the processes occurring in leaching and dissolution. The three major mechanisms of surface attack - ion-exchange, base catalysed hydrolysis of the network or lattice, and recrystallisation - are compared. Cation-exchange is very fast but limited to a layer no more than 20nm ahead of the reacted layer. Reaction of the titanate lattice is relatively slow and, in ceramics, appears to be limited by the grain size of the perovskite phase. In situ recrystallisation of amorphous TiOx films to TiO2 is fast above 100°C giving a polycrystalline discontinuous layer of varying depth (up to the grain size)

Omvendt voldsalarm - behov for en utvidelse av dagens rettstilstand?

MasteroppgaveJUS399MAJURMAJUR-

Illegal streaming as disruptive innovation : How the established companies within the television industry deal with potential disruptive innovations

This thesis was written to examine how the established companies within the television industry in Norway deal with potential disruptive innovations. In this case the disruptive innovation is illegal streaming of sports, series and movies. This is common among the younger population, which is not the incumbents’ main target. In that way, illegal streaming can grow without them knowing it, and in worst case eventually push them out of the market. Especially when the users can “save” 900 NOK on sports or 300-400 NOK on series a month on the illegal market. In order to analyze this, there were performed five semi-structured interviews with important players in the market. To map how the Internet-users relate to and use streaming, a survey was made and shared through social media. All of these can be found in the Appendix. The results from the survey shows that all of the respondents have used streaming, due to availability and that the price is low (or free). In general the illegal sites were used more than the Norwegian services, like Comoyo and CMore Play. The interviews indicates that the established companies are doing measures to prevent loosing customers by making content available on several platforms, by making apps and adjusting to the habits people have. They are also monitoring the legal and illegal streaming market and encrypting their content. They do however not see the illegal streaming market as competitors, which is a bit frightening given that the survey indicates that these pages are used more than the ones they consider competitors. It seems like they don’t take them as seriously as they should. This trend can evolve fast and if it grows beyond the innovators-phase and over to early adopters, they can in principle loose over 500.000 customers and also 2 835.000.000 NOK a year. Recommendations for the established companies are 1. Stop illegal streaming (basically impossible) 2. Keep the price low enough for people to choose them 3. Improve service – better payment solutions, quality, selection and availability. 4. A “package-deal” between the 5. Get eaten up services where the users can get discounts would be optimal. The limitations of this thesis include: given only a few interviewees and a small amount of respondents (60) of the survey, the results from this thesis cannot be generalized to the population as a whole. Also, the analyze was conducted over a five- months period, which also make time a limitation. However, this thesis can be a good foundation for further work within this field

Versatile in situ powder X-ray diffraction cells for solid–gas investigations

Two multipurpose sample cells of quartz (SiO2) or sapphire (Al2O3) capillaries, developed for the study of solid–gas reactions in dosing or flow mode, are presented. They allow fast change of pressure up to 100 or 300 bar (1 bar = 100 000 Pa) and can also handle solid–liquid–gas studies