1,721,973 research outputs found
Dataset for Laser-Driven Phase Segregation and Tailoring of Compositionally Graded Microstructures in Si-Ge Nanoscale Thin Films
No full textDataset supports: Aktas, Ozan, Oo, Swe, MacFarquhar, Stuart, James, Mittal, Vinita, Chong, Harold and Peacock, Anna(2020). Laser-Driven Phase Segregation and Tailoring of Compositionally Graded Microstructures in Si-Ge Nanoscale Thin Films. ACS Applied Materials & Interfaces. DOI: http://dx.doi.org/10.1021/acsami.9b22135</span
The fieldwork effect : an exploration of the role and impact of fieldwork at key stage two
No full textThis thesis explores the heuristic potential of geographical fieldwork in a cross curricular residential setting. The enquiry concentrates upon students in the upper primary range (ages nine to eleven), and examines the impact of the pedagogy and its contextual framework upon both cognitive and affective learning. It relates its results to the attempts to raise learning quality via programmes such as the Cognitive Acceleration in Science Education project (Adey and Shayer, 1994), and to similar recent work in geography by Leat (1996;1997).The work utilised a research framework drawn from both quantitative and qualitative perspectives. A quasi-experimental structure, combined with a 'case study' approach, permitted an investigation of both learning outcomes and processes operating during a residential, cross-curricular field course, and allowed for a comparison between students within that setting and a similar group in a more 'normal' school/home environment. Statistical manipulation and analysis of quantitative data, allied to phenomenological analysis of qualitative data, permitted conclusions to be drawn to a number of key questions derived from the research objectives.Results show that residential fieldwork is capable not only of generating positive cognitive and affective learning amongst students, but that this may be enhanced significantly compared to that achievable within a classroom environment. Fundamental to this is an identified relationship between the two principal learning domains, and it is argued that the role of affective learning is pivotal to the cognitive development process. The thesis also contemplates the possibility that the approach and structure employed in effective fieldwork may have a wider educational application in the context of 'raising attainment' amongst school students. Grounded theory indicates that fieldwork should be seen as a pedagogy central to the current debate over learning quality within schools, and that it is crucial to give all children the opportunity to be exposed to the broad learning techniques and structures associated with fieldwork if we truly wish to raise attainment.</p
The long-term evolution of Montserrat volcanism
No full textThis thesis investigates the long-term geochemical trends of volcanism on Montserrat and Guadeloupe, islands in the northern Lesser Antilles arc, through both their terrestrial and marine (from International Ocean Discovery Program core U1396C) records, to examine the processes driving geochemical evolution in island arcs.Detailed mapping of the Silver Hills, the least studied volcanic centre on Montserrat, reveals activity was dominated by andesite dome growth and collapse. New 40Ar/39Ar ages from terrestrial samples, combined with new palaeomagnetic and biostratigraphic ages of tephra layers from marine sediment core U1396C, reveal the previously unrecognised overlap in volcanic activity between the Silver and Centre Hills, and Centre and Soufrière Hills.Pb-Nd-Sr isotope and major and trace element data for the Silver Hills show that lavas fall into two compositional groups; ‘normal’ lavas and ‘low Al2O3-high Fe2O3’ lavas. The latter group formed from parental magmas which experienced up to 25% greater plagioclase fractionation compared to the parent magmas of the normal lavas, likely as a result of lower magmatic H2O content. There is no systematic geochemical variation between lava domes of the Silver Hills, but there is an observed systematic shift in 143Nd/144Nd to progressively less radiogenic values with time, which is inferred to result from mantle heterogeneity.Tephra layers from core U1396C have been analysed for Pb-Nd-Sr isotope and major and trace element data, which provide a record of the geochemical evolution of volcanism on Montserrat and Guadeloupe over the past ~4.5 Ma; 2.3 and 1.7 Ma longer than their respective terrestrial records. The main geochemical change for the Montserrat source region occurred ~4.5–3.9 Ma, resulting from an increase in slab sediment contribution to the mantle wedge via an aqueous fluid. Tephra layers from Guadeloupe display greater temporal geochemical variation, driven by crustal assimilation of mid-ocean ridge basalt.Componentry, grain size and grain morphology analyses of the thickest tephra layer in core U1396C derived from Guadeloupe, T2.36, reveal it was formed by deposition from fallout from an eruption column, followed by a co-ignimbrite ash cloud from the same eruption. Eruption reconstructions suggest that this deposit likely formed from a VEI 6 eruption
Direct laser writing in semiconductors for photonics applications
No full textResearch in silicon photonics is accelerated by the extensive understanding of silicon fabrication from the microelectronics industry, and silicon appears to be ideally placed to offer a solution for the integration of photonic layers onto an electronic chip. However, the manufacture of a crystalline silicon film requires high temperatures incompatible with back-end-of-line integration with the complementary metal-oxide semiconductor process flow. Significant interest therefore lies in research into low-temperature fabrication of alternatives to crystalline silicon. This thesis presents a direct laser crystallisation technique suitable for use in a low-temperature fabrication process flow, and demonstrates its applications in a range of semiconductor materials. Laser writing is used to define waveguides in thin films of hydrogenated amorphous silicon, which has attracted attention for optical applications due to its low transmission losses and high nonlinear refractive index. A lithography-free waveguide definition process is proposed, and the optical loss of the resulting waveguides is measured and compared to those in conventionally fabricated waveguides. The laser crystallisation process is then applied to etched wire structures in low temperature deposited amorphous silicon, maintaining a substrate temperature below the thermal budget for back-end-of-line integration. The material and optical properties of the resulting polycrystalline material are investigated by Raman spectroscopy, X-ray diffraction crystallography, cutback transmission measurements and nonlinear optical characterisation, and found to be comparable to those of single-crystal silicon. Most significantly, the lowest losses to date are recorded at 2.4 dB cm-1, and third-order nonlinear characteristics in or near the range reported for crystalline silicon are measured. Finally, the application of the laser writing process to silicon-germanium is investigated. Silicon-germanium is a binary alloy with composition-dependent properties and applications. The laser writing system is used to carry out localised tailoring of the germanium fraction. The change in local composition is investigated by Raman spectroscopy, electron microscopy and finite-element simulation, and the effect on the photoconductivity is studied
Map of North America
No full textRelief shown by hachures.; Prime meridian: Greenwich.; "Shows Mr. Stuart's route through the United States and Canada in 1828, 29 & 30."; "Shows the boundary of the United States both on the side of the British Possessions , & those of Mexico."; Probably taken from James Stuart's Three Years in North America
Stuart (James D.) en Sloan (W. David). Historical methods in mass communication
No full textBurgelman Jean-Claude. Stuart (James D.) en Sloan (W. David). Historical methods in mass communication. In: Revue belge de philologie et d'histoire, tome 70, fasc. 2, 1992. Histoire médiévale, moderne et contemporaine — Middeleeuwse, moderne en hedendaagse geschiedenis. pp. 567-568
Stuart (James D.) en Sloan (W. David). Historical methods in mass communication
No full textBurgelman Jean-Claude. Stuart (James D.) en Sloan (W. David). Historical methods in mass communication. In: Revue belge de philologie et d'histoire, tome 70, fasc. 2, 1992. Histoire médiévale, moderne et contemporaine — Middeleeuwse, moderne en hedendaagse geschiedenis. pp. 567-568
High throughput and traditional routes towards functional oxide and oxide-nitride materials
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
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