Showing papers by "Peter Davies published in 2004"

Effects of patchy shade on stream water temperature: how quickly do small streams heat and cool?

Abstract: Summer field observations in five 2nd order streams (width 1–2 m, depth 5–15 cm, velocity 5–10 cm s–1) in Western Australia and south-east Queensland showed that daily maximum temperatures changed by ±4°C over distances of 600–960 m (travel time 2–3 h) immediately downstream from 40–70% step changes in riparian shade. There was a strong linear relationship between the rate of change of daily maximum temperature and the change of shade such that downstream from a 100% change of shade the heating/cooling rates are ±4°C h–1 and ±10°C km–1 (upper bound ±6°C h–1 and ±15°C km–1) respectively. These high rates only apply over short distances and travel times because downstream water temperatures adjust to the new level of shade and reach a dynamic equilibrium. Shade was too patchy in the study streams to measure how long water takes to reach equilibrium, however, using an existing computer model, we estimate that this occurs after ~1200 m (travel time 4 h). Further modelling work is desirable to predict equilibrium temperatures under given meteorological, flow and shade conditions. Nevertheless, landowners and regulators can use this information to determine whether the presence/absence of certain lengths of bankside shade are likely to cause desirable/undesirable temperature decreases/increases.

Improving narrative skills in young children with delayed language development

Abstract: A substantial number of 5–7 year old children experience delayed language development which threatens their progress in school, although they have not been placed on speech and language therapy caseloads. Children with delayed language development typically have a limited ability to understand and tell stories. Intervention to develop the oral narratives of these children can significantly improve their ability to understand and tell stories. This development improves their ability to participate in, and benefit from, mainstream classroom activities. We report on a style of intervention which aims to achieve these objectives. The intervention applies a story grammar approach through a collaboration between teachers, learning support assistants and speech and language therapists. The intervention took place in UK schools with a high proportion of children from families with low socio‐economic status and this article reports significant improvements in the quality of these children's story‐telling.

Application of Interlaminar Tests to Marine Composites. A Literature Review

Abstract: This paper gives an overview of the characterization of the interlaminar properties of composites used for marine structures. Composites to be used in marine applications have particular requirements due to their environment, their large dimensions, mechanical loading and cost constraints. Under certain loading conditions (insert loading, impact) there is a risk of delamination as interlaminar strength of these materials is limited. This paper presents an overview of the tests available to measure delamination resistance. The parameters which influence this property, including the constituents (fibre, matrix, interface), specimen geometry, fabrication route and the resulting defects, and aging are reviewed here.

Application of Interlaminar Tests to Marine Composites. Relation between Glass Fibre/Polymer Interfaces and Interlaminar Properties of Marine Composites

Abstract: The need for improved performance and the development of new composite manufacturing methods require a better understanding of the role of interface phenomena in the mechanical behaviour of these materials. The influence of the cure cycle on the bulk and surface properties of the matrix resin, and of composites based on polyester and epoxy resins reinforced with glass fibres has been studied. While the mechanical properties of the epoxy vary with cure temperature the surface tension is not affected. The increase in interfacial shear strength and interlaminar shear strength with increased cure temperature cannot be simply explained by the wetting of the fibres by the matrix. The importance of thermal stresses, generated at the interface by resin shrinkage and differences in thermal expansion, for the mechanical behaviour of the composite are demonstrated.

Nutrient processes and chlorophyll in the estuaries and plume of the Gulf of Papua

Abstract: This paper investigates the waters of the Gulf of Papua during three cruises of the TROPICS (Tropical River Ocean Processes In Coastal Settings) programme Plume characteristics were investigated during Leg 1 (May 1997), and estuarine properties during Leg 5a (September 1997) and Leg 7 (January 1999) During Leg 1 the plume was apparent as a well mixed layer up to 30 m deep extending offshore to a distance of 150 km off the Fly River Lowest salinities were found off the Taruma Delta Highest chlorophyll concentrations were found at the inner plume close to the river mouth Dissolved phosphate and nitrate are removed in this zone, whereas silicate behaves conservatively Primary productivity within the plume appears to rely upon recycled nutrients, with organic fractions representing the majority of the nutrient pool In the estuaries nutrients were found to behave differently during the monsoon than during the low flow of the extremely dry conditions associated with the 1997 El Nino event Normally the Fly is characterised by remineralisation of organic nitrogen in the upper estuary, but during drought conditions DON production and NH 4 + uptake suggest that bacterial activity is more prevalent Ocean Colour and Temperature Scanner imagery shows a number of features of the plume, but generally overestimates chlorophyll concentrations due to the effects of high suspended sediment concentrations and, to a lesser extent, coloured dissolved organic matter

The Myth of the Bog Standard Secondary School: a school level analysis of students' choice of optional subjects

Abstract: We present results of an ESRC-funded study into variations in student enrolment and attainment in different subjects. Recent English policy proposals indicate a further extension of specialist secondary schools and relaxation of the National Curriculum requirements for students aged 14-16. These initiatives, together with negative comments related to ‘bog standard comprehensives’, seem to imply that a lack of choice or variation in English secondary schooling was constraining attempts to raise educational attainment levels. Policy appears again to have outstripped evidence since we know relatively little about the extent and consequences of student choice within secondary schools. In principle, increased within-school choice can raise educational attainment levels if it enables parents, students, teachers and heads to improve the match between the curriculum studied and the particular aspirations and abilities of students. We explore the extent and determinants of within-school choice using crosssectional data drawn from the YELLIS database held by the Curriculum, Evaluation and Management Centre at the University of Durham. Our analysis reveals large variation between schools in GCSE exam entries in Geography, History, Modern Foreign Languages, Business Studies and Home Economics. We show that the proportions of this variation that are due to school level factors (such as school governance and size) and the characteristics of the cohort of pupils attending a school are both relatively small. We consider the implications of these results for policy on curriculum specialisation between and within schools.

Structural mechanical testing of a full-size adhesively bonded motorboat

Abstract: This paper describes the tests performed on a full-size motorboat to demonstrate the potential for adhesive bonding to replace overlaminated connections. Adhesive bonding resulted in a significant reduction in assembly time for bulkhead connections compared with overlamination. Drop tests and sea trials were performed using specially adapted strain gauge instrumentation. These indicated low adhesive joint strain levels, even for severe test conditions. No damage was observed. The data obtained will be used to improve laboratory test procedures to simulate service loading of boat structures.

Assessment of Cable Models For Synthetic Mooring Lines

Abstract: This study deals with the modeling of the static behavior of synthetic wire ropes. The objective is the determination of the validity domain of two analytical models (Costello and Labrosse) used to predict the overall axial stiffness. First investigations have been performed for isotropic material. The results of the two analytical models are compared with a three-dimensional finite element cable model, using a non-dimensional analysis. Next, Labrosse's model is extended for synthetic fibers rope applications. Tests performed to obtain experimental stiffness measurements are then presented. Finally, predicted stiffness is compared to test results thus validating the analytical approach.

Design, manufacture and testing of stiffened panels for marine structures using adhesively bonded pultruded sections

Abstract: This paper presents results from a programme designed to evaluate the use of bonded pultrusion sections to replace overlaminated stiffeners on composite sandwich panels for marine applications. First, the existing solution is described and results from uniform pressure loading tests of these panels are presented. Second, the design of bonded pultruded stiffeners is discussed, including results from preliminary tests to evaluate adhesives, and finite element calculations to optimize stiffener geometry. Finally, results from tests on two bonded stiffened panels are given and failure loads and mechanisms are compared to predictions.