Molecular dynamics simulation of nanocolloidal amorphous silica particles: Part II

Explicit molecular dynamics simulations were applied to a pair of amorphous silica nanoparticles of diameter 3.2 nm immersed in a background electrolyte. Mean forces acting between the pair of silica nanoparticles were extracted at four different background electrolyte concentrations. Dependence of the inter-particle potential of mean force on the separation and the silicon to sodium ratio, as well as on the background electrolyte concentration, are demonstrated. The pH was indirectly accounted for via the ratio of silicon to sodium used in the simulations. The nature of the interaction of the counter-ions with charged silica surface sites (deprotonated silanols) was also investigated. The effect of the sodium double layer on the water ordering was investigated for three Si:Na+ ratios. The number of water molecules trapped inside the nanoparticles was investigated as the Si:Na+ ratio was varied. Differences in this number between the two nanoparticles in the simulations are attributed to differences in the calculated electric dipole moment. The implications of the form of the potentials for aggregation are also discussed.Comment: v1. 33 pages, 7 figures (screen-quality PDF), submitted to J. Chem. Phys v2. 15 pages, 4 tables, 6 figures. Content, author list and title changed; single space

Compositions Utilizing Fractal Flame Algorithms

“Music, by its very abstract nature, is the first of the arts to have attempted reconciliation of artistic creation with scientific thought” – Xenakis, 1992 This portfolio explores how the iterative and recursive processes employed within fractal flame algorithms can be used to create new and aesthetically pleasing micro and macro sounds from which coherent compositions can be created. A variety of existing electronic compositional procedures, including wave-set substitution and granular synthesis, as well as a number of classical compositional practices, such as hocketing, are deployed to generate a complex and diverse set of compositions. The portfolio shows how marrying these sound manipulating techniques and compositional processes with the sonic events produced by the unexplored field of fractal flame algorithms has allowed me to generate – in the words of Iannis Xenakis – ‘sounds that have never existed before’. The portfolio shows the creative potential fractal flame programs have for electronic music generation and how they offer a terra nova (new earth) upon which computergenerated music can lay down solid foundations and expand in new directions to harvest exciting results

The Fractal Geometry of Life

The goal of this design project was to bridge the intentions of mathematical theory and wearable art design by experimenting with the mergence of fractal art theory and the aesthetic of the artwork of Piet Mondrian to create an interesting, complex, and aesthetically pleasing visual form of wearable art. The garment patterns were created using Lectra Modaris and exported into DXF format for motif arrangement in Adobe Illustrator. The designers utilized laser cutting technology to represent the effects of the fractal geometric art and the concept from Mondrian’s painting. The primary colors inspired by the Mondrian’s painting were filled in a particular block on the dress using round glass seed beads. This wearable art design contributes an innovative design process that relies on computer software to give rise to the chaos and regularity, the fractal dimension and infinity, which is analogous to the fractal art design process. Keywords: Fractal art, golden ratio, laser cutting, hand beadin

An Approach to the Procedural Generation of Worn Metal Surfaces

Motivated by the phenomenon that wear and tear tends to happen more near sharp cornersof a surface, this thesis presents a method for procedurally generating photorealistic metal surfacesbased upon evaluating curvature values. The thesis describes the development of eight metal shadersthat are used to replace the manual texture painting typically used in production. The approach isdemonstrated by applying these metal shaders to a robotic dog model from a short film involvinglive action and CG elements. Frames from a short animation of the robotic dog are presented, anda discussion of the strengths and weaknesses of this methodology

Imperceptible Realities: An exhibition – and – Digitalisation: Re-imaging the real beyond notions of the original and the copy in contemporary printmaking: An exegesis

This PhD practice-led research project provides a broad overview of how newer print technologies can bring about enhanced understandings of the world whilst simultaneously questioning the value of such processes in contrast to traditional means of image making. My curiosity pivots on the worry that something essential about representation of the real might be lost if humanity were to embrace digital methods only. Through my creative project I address my concerns to re-image representations of the real beyond notions of the original and the copy through contemporary printmaking. The research culminated in the exhibition Imperceptible Realities and an exegesis. In examining Jean Baudrillard’s concept of simulacra this research argues for the continuing relevance of traditional etching techniques through a pivotal case study that scrutinised Rembrandt van Rijn’s etching The Shell (Conus marmoreus). In contrasting traditional etching techniques with newer methods of digital printmaking a significant copy, derived from a similar shell specimen that Rembrandt had observed, manifested itself in contemporary 3D print. The copying process focused the investigation into questioning the aesthetic value of this new shell in digitalised 3D form. In the contemporary printmaking field there is evidence for the continued integration of traditional and digital approaches to printmaking. New pathways were examined in printmaking to allow creative explorations of visual boundaries between contemporary images affected by digital erasure. The innovative use of photogrammetry software focused the investigation into the effects of digital capabilities on image making. The effect of examining the digital relationship in contemporary printmaking revealed that ignoring aesthetic differences between the original and copy brought about by digitised re-imaging are seemingly lost at the expense of disengagement with the physical world. As a result digital and traditional spaces that meet collaboratively through print are advantaged in the 3D printed copy itself and employed to create new understandings in creative practice. Viewing observed differences in the 2D and 3D printed copy itself became key in creating new images, beyond a hybridised printmaking process—such understandings that examined the divisive relationship between digital and traditional printmaking processes becomes invigorated with possibility. This research posits such a position by suggesting that if traditions in the printmaking field are ignored by the continued digitalisation of images through and within the employment of technologies, something is lost. Perceptual experiences of the physical world are seemingly misplaced at the expense of replacing such immediate experience with simulacra and an inward bias toward the screen. Adopting a practice-led research methodology revealed the subtleties of the ongoing relationship of digital capabilities affecting the materiality of traditional printmaking. The applications of innovative interdisciplinary discoveries to my contemporary arts practice drew on strong partnerships and collaborative relationships developed with the fields of chemistry, engineering and science. I applied these discoveries to my contemporary arts practice to examine the effects of digital capabilities and the materiality of traditional printmaking. To embrace conceptual growth creative work the research drew on philosopher Gilles Deleuze and psychiatrist Félix Guattari’s notion of the rhizome. The presence of simulacra in the world has continued to expand as digital technologies proliferate. The application of traditional printmaking and digital printmaking through open thinking offers a different way to understand physical aspects of the world and create propositions that go beyond re-imaging the real

Solute transport in layered and heterogeneous soils

Better understanding of transport of dissolved chemicals in soils and aquifers is important to evaluate and remediate contaminated soils and aquifers. Because of the nature of heterogeneity of field porous media, studies on transport processes in non-homogeneous media are necessary. In this study, transport of solutes in layered and heterogeneous media was investigated using numerical approximations. For layered soils, transport properties were assumed homogeneous within individual layers but different between layers. For heterogeneous systems, either a time-dependent or distance-dependent dispersivity was considered to represent the effects of heterogeneity. In a series of simulations of transport in two-layered soils, we found that breakthrough curves (BTCs) were similar regardless of the layering sequence for all reversible and irreversible solute retention mechanisms. Such findings were in agreement with results from laboratory experiments using tritium as a tracer and Ca and Mg as reactive solutes. Field measured apparent dispersivity is often found to increase with time because of the heterogeneity of soils and aquifers. We proposed a fractal model to explain the time dependency of dispersivity. Our model indicates a nonlinear increase of variance of travel distance with time or mean travel distance, which implies a time-dependent dispersivity. Application of our model to three field experiments (the Cape Cod, the Borden, and the Columbus sites) indicates fractal behavior for all three cases. The term scale effects is often used in the literature to refer to the dependency of dispersivity on either mean travel distance or distance from source. We presented a critical review on the ambiguity in definition of this term. We presented comparisons between transport processes in systems with time-dependent and distance-dependent dispersivities. Our results showed that enhanced spreading in BTCs consistently occurred in systems with time-dependent dispersivities. Recently, a new governing equation, factional-order advection-dispersion equation (FADE) was proposed to describe transport processes in heterogeneous systems. We proposed a statistical method to justify the use of a FADE. A fractional order of 1.82 was confirmed to be necessary to describe the bromide plumes at the Cape Cod site

X-ray and light scattering from nanostructured thin films

The object of this thesis is the study of nanostructured thin films using inelastic fight scattering and elastic x-ray scattering techniques. Their use in combination with other techniques is a powerful tool for the investigation of nanostructured materials. X-ray, Raman and Brillouin characterisation of cluster-assembled carbon films, promising for applications in the field of catalysis, hydrogen storage and field emission, is here presented. X-ray reflectivity (XRR) provided a measure of the density. Raman spectroscopy showed that the local bonding in these amorphous films depends on the size distribution of the clusters and that it is possible to select the cluster size in order to grow films with tailored properties. Brillouin scattering provided a characterisation at the mesoscopic scale and an estimate of the elastic constants, revealing a very soft material. XRR was employed to study density, layering and roughness of a wide range of amorphous carbon films grown with different techniques. Some films possess an internal layering due to plasma instabilities in the deposition apparatus. By comparing XRR with Electron Energy Loss Spectroscopy, a unique value for the electron "effective mass" was deduced and a general relationship between sp(^3)-content and density was found. XRR and H effusion were used to determine the hydrogen content. A study of the size-dependent melting temperature in tin nanoparticle thin films was undertaken with a combined use of X-Ray Diffraction (XRD) and light scattering. A redshift in the position of a Rayleigh peak in the temperature-dependent Brillouin measurements was shown to be related to the melting of the nanoparticles and explained by an effective medium model. XRD also provided information on the low-level of stress in the particles. Low-frequency Raman scattering was used to study the behaviour of the acoustic modes of a single particle as a function of temperature

Fractal Patterns from the Dynamics of Combined Polynomial Root Finding Methods

Fractal patterns generated in the complex plane by root finding methods are well known in the literature. In the generation methods of these fractals only one root finding method is used. In this paper, we propose the use of a combination of root finding methods in the generation of fractal patterns. We use three approaches to combine the methods: (1) the use of different combinations, e.g. affine and s-convex combination, (2) the use of iteration processes from fixed point theory, (3) multistep polynomiography. All the proposed approaches allow us to obtain new and diverse fractal patterns that can be used, for instance, as textile or ceramics patterns. Moreover, we study the proposed methods using five different measures: average number of iterations, convergence area index, generation time, fractal dimension and Wada measure. The computational experiments show that the dependence of the measures on the parameters used in the methods is in most cases a non-trivial, complex and non-monotonic function