Atomisation of molten Zinc

Zinc dust is produced by an atomisation process in which air at 17 atmospheres pressure is directed through a narrow annular nozzle surrounding a stream of molten zinc. Industrially, it is important to control the size distribution of zinc particles. It is therefore necessary to understand the features of the process, guided where appropriate by simple mathematical models and estimates. This report examines qualitative features using simple models for number of drops produced, estimates for air speed and swirl, heat transfer in the molten zinc and droplets, and droplet collisions and stability. Results from a literature survey are presented. At this stage, the construction of more elaborate mathematical models for the process is not warranted; rather, we expect that better understanding of the process requires an experimental program involving flow visualisation

Microwave heating of flowing slurry

Mathematical models are constructed to investigate the use of microwaves to dissolve chemical crystals in a flowing solvent. The slurry is considered to be a Newtonian fluid in which the solvent is heated by microwaves. The solute crystals dissolve at a rate which depends strongly on temperature, and the dissolution has a profound effect on the viscosity of the slurry. Special consideration is given to crystal size and heating effects close to the walls containing the slurry. A simplified version of the mathematical model is solved numerically, and the results lead to suggestions for improved design of the process. We also investigate the implications of non-Newtonian fluid models. The overall outcome of the work is a better understanding of the heat and mass transfer of the slurry, as well as recommendations on crystal size and design of the process

Beyond the happy sheets! Evaluating learning in information skills teaching

This paper reviews three years of data measuring students' immediate reactions to a computer-assisted learning package in information skills and reports on work in progress to establish a more comprehensive programme of evaluation which will assess the longer term impact on learning of both the courseware itself and the way the courseware is delivered to students. The GAELS courseware was developed in the late 1990s as part of a collaborative project between the Universities of Glasgow and Strathclyde, with funding from the Scottish Higher Education Funding Council. The courseware was designed to teach higher level information skills and was initially developed for use with postgraduate engineering students; it has subsequently been adapted for use with students in other subject areas, including biological and physical sciences, and has been embedded for several years now in workshop sessions undertaken with postgraduate and undergraduate students across the Faculties of Science and Engineering at the University of Strathclyde. The courseware is introduced at the start of the academic session and made available on the Web so that students can use it as needed during their course and project work. During the first year, the courseware was used in isolation from other teaching methods (although a librarian was present to support students), whilst in the second and third years it was integrated into more traditional workshop-style teaching sessions (led by a librarian). Following work described in Joint (2003), library staff now wish to assess the longer term impact on learning of both the courseware itself and the way the courseware is delivered to students. However, the existing evaluation data does not adequately support this type of assessment. Teaching sessions are routinely evaluated by means of simple feedback forms, with four questions answered using a five-point Likert scale, collected at the conclusion of each session. According to Fitzpatrick (1998), such feedback forms measure students' reactions and represent but the first level of evaluation. Learning, which can be defined as the extent to which a student changes attitudes, improves knowledge and/or increases skill as a result of exposure to the training, is the second level and is not being measured with these forms. A more comprehensive programme of evaluation, including logging usage of the courseware outside teaching sessions and follow-up of students several months after their introduction to the courseware, is now being established to support a more meaningful assessment of impact of the courseware on student learning

Oil Blending: Mixing and Contamination

The Shell Company of Australia has a frequent need to blend lubricants. Blending, sometimes involving three lubricant oils and additives, takes place by jet mixing in large tanks of typically 45,000 titres capacity. The jets are driven by pumps with typical volume throughput of up to 1,000 titres per minute, and typical blending times may be as long as one or two hours. The jet blending process was investigated in a number of ways at the Study Group. These included: simple estimates for blending times, theoretical and experimental description of jet behaviour, development of a simple compartment model for the blending process, and several large scale computer simulations of the jet-induced motion using a commercial Computational Fluid Dynamics package. In addition, the sedimentation of contaminant particles in the tanks was investigated. This overall investigation, using a variety of approaches, gave a good knowledge of the blending process

Unambiguous one-loop quantum energies of 1+1 dimensional bosonic field configurations

We calculate one-loop quantum energies in a renormalizable self-interacting theory in one spatial dimension by summing the zero-point energies of small oscillations around a classical field configuration, which need not be a solution of the classical field equations. We unambiguously implement standard perturbative renormalization using phase shifts and the Born approximation. We illustrate our method by calculating the quantum energy of a soliton/antisoliton pair as a function of their separation. This energy includes an imaginary part that gives a quantum decay rate and is associated with a level crossing in the solutions to the classical field equation in the presence of the source that maintains the soliton/antisoliton pair.Comment: Email correspondence to [email protected] ; 10 pages, 2 figures, REVTeX, BoxedEPS; v2: Fixed description of level crossing as a function of $x_0$; v3: Fixed numerical error in figure dat

A new model for evolution in a spatial continuum

We investigate a new model for populations evolving in a spatial continuum. This model can be thought of as a spatial version of the Lambda-Fleming-Viot process. It explicitly incorporates both small scale reproduction events and large scale extinction-recolonisation events. The lineages ancestral to a sample from a population evolving according to this model can be described in terms of a spatial version of the Lambda-coalescent. Using a technique of Evans(1997), we prove existence and uniqueness in law for the model. We then investigate the asymptotic behaviour of the genealogy of a finite number of individuals sampled uniformly at random (or more generally `far enough apart') from a two-dimensional torus of side L as L tends to infinity. Under appropriate conditions (and on a suitable timescale), we can obtain as limiting genealogical processes a Kingman coalescent, a more general Lambda-coalescent or a system of coalescing Brownian motions (with a non-local coalescence mechanism).Comment: 63 pages, version accepted to Electron. J. Proba

Coalescent simulation in continuous space:Algorithms for large neighbourhood size

Many species have an essentially continuous distribution in space, in which there are no natural divisions between randomly mating subpopulations. Yet, the standard approach to modelling these populations is to impose an arbitrary grid of demes, adjusting deme sizes and migration rates in an attempt to capture the important features of the population. Such indirect methods are required because of the failure of the classical models of isolation by distance, which have been shown to have major technical flaws. A recently introduced model of extinction and recolonisation in two dimensions solves these technical problems, and provides a rigorous technical foundation for the study of populations evolving in a spatial continuum. The coalescent process for this model is simply stated, but direct simulation is very inefficient for large neighbourhood sizes. We present efficient and exact algorithms to simulate this coalescent process for arbitrary sample sizes and numbers of loci, and analyse these algorithms in detail

ExoMol line lists II: The ro-vibrational spectrum of SiO

Accurate rotation-vibration line lists are calculated for silicon monoxide. Line lists are presented for the main isotopologue, $^{28}$Si$^{16}$O, and for four monosubsituted isotopologues ($^{29}$Si$^{16}$O, $^{30}$Si$^{16}$O, $^{28}$Si$^{18}$O and $^{28}$Si$^{17}$O), in their ground electronic states. These line lists are suitable for high temperatures (up to 9000 K) including those relevant to exoplanetary atmospheres and cool stars. A combination of empirical and \textit{ab initio} methods is used: the potential energy curves are determined to high accuracy by fitting to extensive data from the analysis of both laboratory and sunspot spectra; a high quality {\it ab initio} dipole moment curve is calculated at the large basis set, multi-reference configuration interaction level. A partition function plus full line lists of rotation-vibration transitions are made available in an electronic form as supplementary data to this article and at \url{www.exomol.com}.Comment: MNRAS (in press