2,249 research outputs found
Intelligent student systems : an application of viewpoints to intelligent learning environments
No full textIntelligent Student Systems are a class of Intelligent Learning Environments that place the learner in the role of a tutor rather than a student. In an analogy with the educational practice of peer tutoring users learn by teaching the computer -- inverting the predominant `computer as tutor' metaphor. Intelligent Student Systems emphasize the learner's viewpoint in educational interactions in preference to the system's conception of the domain. These systems are considered to be less complex than Intelligent Tutoring Systems and to have the potential to generate novel human-computer educational interactions. Viewpoints also have an integral part in knowledge representation in Intelligent Learning Environments and they are utilised in the design and implementation of an Intelligent Student System in economics. Testing of the system produced insights into the future application of Intelligent Student Systems
Holmium-doped 2.1 micrometers waveguide chip laser with an output power > 1 W
No full textPublished 10 Dec 2015Abstract not availableD.G. Lancaster, V. J. Stevens, V. Michaud-Belleau, S. Gross, A. Fuerbach, and T.M. Monr
Small-scale heterogeneity in sediments : experimental and modelling investigations
No full textThis thesis consists of several studies relating to small-scale heterogeneity in sediments. The principal aim was to further our understanding of processes occurring at microniches. The individual studies consist of: 1) a critical review of previous studies of microniches that used probes with high spatial resolution and modelling approaches; 2) an experimental study of analysis of oxyanions in sediment at high resolution that applied a newly developed preparation method for a combined AgI/FeOOH binding phase, to investigating processes occurring at a sulphidic microniche within a freshwater sediment; 3) analysis of the relationship between trace metal (cobalt) and iron and manganese in a marine sediment using DGT, although this is not directly related to microniches, these data are useful in modelling the release of microniche trace metal from authigenic oxides; 4) the development and application of a three-dimensional diagenetic model to investigate conceptually the geochemical behaviour of microniches under different conditions, and to interpret modelled observations in terms of data from the literature and known trace element geochemistry. The key results/conclusions from both the laboratory and modelling studies are: 1) for a freshwater sediment, depletions in anions (of P, V, As) at a microniche of elevated sulphide were observed and the behaviour of phosphate at this niche was attributed to uptake associated with elevated activity of sulphate reducing bacteria; 2) modelled scenarios, with varying microniche properties, were shown to be relevant to experimental observations reported in the literature. The preferential deposition of FeS at the edge of microniches (with lifetimes of 2.5-5 days), forming ‘crustal’ deposits was demonstrated. The modelled data indicated that microniches may be significant in terms of the formation of some trace element sulphides. This thesis also contains an assessment of the significance of microniche processes and a discussion of priorities for future work
A miniature chip-scale mid-infrared glass laser
No full textOral presentation in Technical Session 4 – Laser Development. Monday 9 December 1600-1530D.G. Lancaster, S.Gross, M.W. Withford, T.M. Monro, H. Ebendorff Heidepriem, S. D. Jackso
Retrieval and reference
No full textKnowledge from study may be transferred in different ways: in words and images, via lectures and exhibitions, in the form of articles or books; and electronically.For the time being, the form used most frequently is written publication in text and illustration. However publishing on CD-ROM and the Internet are witnessing rapid development. Maybe this is going to have important consequences for the way in which people are searching for information. In this contribution we discuss some points needing attention for optimal accessibility of knowledge from study and suitably dealing with the sources used. We refer to handbooks for the conventional playing rules of reporting in writing such as clear and interest evoking titles of chapters and paragraphs, clear structure and table of contents, avoiding unnecessary jargon, a clear summary and their like.a,b The emphasis in this Chapter is on adequate pointers to references and the use of key-words.Before embarking, first, something about the way to stimulate potential readers to take notice of the information. It starts already with the cover and the titlepage. These give a first impression of what is waiting for the potential reader. With this author, text or images present themselves. One glance should make clear what the subject is; although it is sometimes attractive to confuse the reader. Starting from cover and title page, the reference data (copyright notice, year of publication, ISBN number, place of issue and publisher), table of contents, foreword (written by a recommending outsider or referee) and introduction, the reader is introduced from his own world into the world of the author. The author and those responsible for the lay-out should picture themselves in this process and shape the publication from the vantage point of potential readers (the target audience), their questions, their pre-suppositions, or lack thereof.Possible pre-suppositions of the reader should be supplemented or corrected. With this it is prevented that potential readers are thinking after a while “What the hell is this?” A clear text on the back cover, an index of key-words, a list of references and a sensible use of footnotes and final-notes are important conditions as well in order to achieve a publication that invites reading.Technical Ecology and Methodology (OLD)Real Estate Managemen
Stiffness-force feedback in UAV tele-operation
No full textAerospace Design, Integration and OperationsAerospace Engineerin
LITERATURE REVIEW: The Use of Cation-Exchange Resins in Natural Water Trace Metals Research. ARTICLE: Determination of Free Ion Trace Metal Concentrations in Freshwaters Using Cation-Exchange Resin Equilibrium. A Preliminary Investigation.
No full textLITERATURE REVIEW: The desire to measure low metal concentrations in natural waters stems principally from the aim to understand the effects of trace metals on aquatic biota and to understand the fate of metal pollutants. Trace metals rarely exist in the free ion form, with distribution of the different species being dependent upon pH, Eh, and the types of organic/inorganic ligands and colloidal surfaces. Use of cation exchange resins, particularly Chelex-100, has been developed over the past few decades and enables preconcentration to yield, upon elution, measurable concentrations of trace metals. These resins can also yield data on the speciation (by measuring lability) of a metal in solution by adjusting the contact time of the sample with the resin. Several speciation schemes have been developed where separation techniques (such as dialysis) are coupled with Chelex-column methods (short contact time) and Chelex-batch methods (long contact time). With the exception of recent equilibrium based studies Chelex is always used in an environment where the number of binding sites is in large excess compared to the number of competing cations, meaning competition effect are not significant, although kinetic factors are important is Chelex lability studies. Nitric acid elution generally yield good recovery rates (>90%) and stepwise elution has been shown to be the most effective for both metal recovery and minimising the eluent volume. The development of DGT speciation studies may bring about a technique that is less complex but easier to undertake and yields simple yet useful complexation data. The potential for IDA-resins to yield free-ion concentrations based on equilibrium-based sorption is a beneficial development that is currently being investigated. This review investigates the use of cation exchange resins by assessing the resin properties, the techniques developed and the optimum sorption conditions. ARTICLE: The dissolved free metal ion in natural waters is often related to bioavailability. However, no method currently exists which allows quick, simple and routine determination of free ion concentrations. This study aims to investigate the potential for an ion exchange resin (Chelex-100) to determine free ion concentrations by allowing the resin to equilibrate in situ with a natural water. The environmental concentrations can then subsequently be determined by back calculation of the concentrations eluted from the resin. The sampler employs resin beads retained between two layers of PE mesh, thus allowing flow through the device when deployed vertically in the flow of a stream. Metals are back extracted into a known volume of 2M HNO3. The Windermere Humic Aqueous model (WHAM6.1) was used to predict values for the equilibrium concentration of resin bound metals. Experimental Mn & Cd values were higher than predicted and Cu & Ni values were three orders of magnitude lower than predicted. However, these data are consistent with WHAM modelled data indicating the trend of resin-metal binding during a deployment. These data indicated that the deployment time was insufficient. The suitability of free ligand stability constants to resin binding and possible method developments are also discussed
Light-sheet skew-ray enhanced pump-absorption for sensing
No full textWe present a new sensing technique exploiting light-sheet excitation of skew rays in a multimode fiber, which can be applied to enhance the sensitivity of a range of sensing mechanisms such as pump absorption. The underlying principle is that a light sheet (i.e., thin plane of light) can selectively concentrate the optimum ray group, giving rise to enhanced interaction between light and matter (e.g., fluorophores). We compared this excitation method with others in terms of attenuation of pump light through Rhodamine B. It was observed that the attenuation experienced by light-sheet skew rays can be up to one order of magnitude higher than that of collimated skew rays, and three orders of magnitude higher than that of normal-incidence rays
Tertiary patterns in inclined layer convection
No full textConvection in an inclined layer generates various types of spatio-temporal patterns due to interaction of buoyancy and shear. At small angles of incline, the secondary instability of the uniform base state occurs in the form of buoyancy dominated longitudinal rolls. Above a critical angle of incline marking a co-dimension 2 point, shear driven transverse roll instabilities take over as the secondary instabilities. Computing the location of the co-dimension 2 point for varying thermal driving and inclination angle and determining all secondary bifurcations together with the resulting tertiary states allows to characterize the nonlinear phase diagram of inclined layer convection system. The semi-analytically computed phase diagram quantitatively matches experimental observations by Daniels et al. Close to the co-dimension 2 point, a subcritical secondary bifurcation leading to bistability is identified. In the bistable region, heteroclinic cycles generate bursting behavior
Assessment of Models for Near Wall Behavior and Swirling Flows in Nuclear Reactor Sub-system Simulations
No full textAccurate simulation of turbulence remains one of the most challenging problems in nuclear reactor analysis and design. Due to limitations in computing resources, Reynolds averaged Navier Stokes models (RANS) continue to play an important role in reactor simulations. The Consortium for advanced simulations of light water reactors (CASL) is a Department of Energy technology hub that is investing in research and developmentof a state-of-the-art computational fluid dynamics capabilityto meet the challenges of turbulent simulation of nuclear reactors. In this presentation, we assess several RANS eddy viscosity models appropriate for single-phase incompressible turbulent flows. Specifically, we compare the single equation Splalart-Allmaras to several variations of the model. The assessment takes into consideration elements of full system reactor cores such as complex geometries, heterogeneous meshes, swirling flow, near wall flow behavior, heat transfer and robustness issues. The goal of this strategically oriented assessment is to provide an accurate and robust turbulent simulation capability for the CASL community. Metrics of performance will be constructed by comparing different models on a strategically chosen set of problems that represent reactor core sub-systems
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